Check-in of initial, unmodified freemodbus-v1.5.0

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@4960 42af7a65-404d-4744-a932-0658087f49c3

25 files changed, 3881 insertions, 1 deletions

diff --git a/apps/ChangeLog.txt b/apps/ChangeLog.txt
index 54161979d..d3a78a28f 100755
--- a/apps/ChangeLog.txt
+++ b/apps/ChangeLog.txt
@@ -250,4 +250,6 @@
 
 6.21 2012-xx-xx Gregory Nutt <gnutt@nuttx.org>
 
-	* include/: Stylistic clean-up of all header files.
+	* apps/include/: Stylistic clean-up of all header files.
+	* apps/modbus and apps/include/modbus:  The beginnings of a port of
+	  freemodbus-v1.5.0.
diff --git a/apps/include/modbus/mb.h b/apps/include/modbus/mb.h
new file mode 100644
index 000000000..8d6be7b42
--- /dev/null
+++ b/apps/include/modbus/mb.h
@@ -0,0 +1,417 @@
+/* 
+ * FreeModbus Libary: A portable Modbus implementation for Modbus ASCII/RTU.
+ * Copyright (c) 2006 Christian Walter <wolti@sil.at>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * File: $Id: mb.h,v 1.17 2006/12/07 22:10:34 wolti Exp $
+ */
+
+#ifndef _MB_H
+#define _MB_H
+
+#include "port.h"
+
+#ifdef __cplusplus
+PR_BEGIN_EXTERN_C
+#endif
+
+#include "mbport.h"
+#include "mbproto.h"
+
+/*! \defgroup modbus Modbus
+ * \code #include "mb.h" \endcode
+ *
+ * This module defines the interface for the application. It contains
+ * the basic functions and types required to use the Modbus protocol stack.
+ * A typical application will want to call eMBInit() first. If the device
+ * is ready to answer network requests it must then call eMBEnable() to activate
+ * the protocol stack. In the main loop the function eMBPoll() must be called
+ * periodically. The time interval between pooling depends on the configured
+ * Modbus timeout. If an RTOS is available a separate task should be created
+ * and the task should always call the function eMBPoll().
+ *
+ * \code
+ * // Initialize protocol stack in RTU mode for a slave with address 10 = 0x0A
+ * eMBInit( MB_RTU, 0x0A, 38400, MB_PAR_EVEN );
+ * // Enable the Modbus Protocol Stack.
+ * eMBEnable(  );
+ * for( ;; )
+ * {
+ *     // Call the main polling loop of the Modbus protocol stack.
+ *     eMBPoll(  );
+ *     ...
+ * }
+ * \endcode
+ */
+
+/* ----------------------- Defines ------------------------------------------*/
+
+/*! \ingroup modbus
+ * \brief Use the default Modbus TCP port (502)
+ */
+#define MB_TCP_PORT_USE_DEFAULT 0   
+
+/* ----------------------- Type definitions ---------------------------------*/
+
+/*! \ingroup modbus
+ * \brief Modbus serial transmission modes (RTU/ASCII).
+ *
+ * Modbus serial supports two transmission modes. Either ASCII or RTU. RTU
+ * is faster but has more hardware requirements and requires a network with
+ * a low jitter. ASCII is slower and more reliable on slower links (E.g. modems)
+ */
+    typedef enum
+{
+    MB_RTU,                     /*!< RTU transmission mode. */
+    MB_ASCII,                   /*!< ASCII transmission mode. */
+    MB_TCP                      /*!< TCP mode. */
+} eMBMode;
+
+/*! \ingroup modbus
+ * \brief If register should be written or read.
+ *
+ * This value is passed to the callback functions which support either
+ * reading or writing register values. Writing means that the application
+ * registers should be updated and reading means that the modbus protocol
+ * stack needs to know the current register values.
+ *
+ * \see eMBRegHoldingCB( ), eMBRegCoilsCB( ), eMBRegDiscreteCB( ) and 
+ *   eMBRegInputCB( ).
+ */
+typedef enum
+{
+    MB_REG_READ,                /*!< Read register values and pass to protocol stack. */
+    MB_REG_WRITE                /*!< Update register values. */
+} eMBRegisterMode;
+
+/*! \ingroup modbus
+ * \brief Errorcodes used by all function in the protocol stack.
+ */
+typedef enum
+{
+    MB_ENOERR,                  /*!< no error. */
+    MB_ENOREG,                  /*!< illegal register address. */
+    MB_EINVAL,                  /*!< illegal argument. */
+    MB_EPORTERR,                /*!< porting layer error. */
+    MB_ENORES,                  /*!< insufficient resources. */
+    MB_EIO,                     /*!< I/O error. */
+    MB_EILLSTATE,               /*!< protocol stack in illegal state. */
+    MB_ETIMEDOUT                /*!< timeout error occurred. */
+} eMBErrorCode;
+
+
+/* ----------------------- Function prototypes ------------------------------*/
+/*! \ingroup modbus
+ * \brief Initialize the Modbus protocol stack.
+ *
+ * This functions initializes the ASCII or RTU module and calls the
+ * init functions of the porting layer to prepare the hardware. Please
+ * note that the receiver is still disabled and no Modbus frames are
+ * processed until eMBEnable( ) has been called.
+ *
+ * \param eMode If ASCII or RTU mode should be used.
+ * \param ucSlaveAddress The slave address. Only frames sent to this
+ *   address or to the broadcast address are processed.
+ * \param ucPort The port to use. E.g. 1 for COM1 on windows. This value
+ *   is platform dependent and some ports simply choose to ignore it.
+ * \param ulBaudRate The baudrate. E.g. 19200. Supported baudrates depend
+ *   on the porting layer.
+ * \param eParity Parity used for serial transmission.
+ *
+ * \return If no error occurs the function returns eMBErrorCode::MB_ENOERR.
+ *   The protocol is then in the disabled state and ready for activation
+ *   by calling eMBEnable( ). Otherwise one of the following error codes 
+ *   is returned:
+ *    - eMBErrorCode::MB_EINVAL If the slave address was not valid. Valid
+ *        slave addresses are in the range 1 - 247.
+ *    - eMBErrorCode::MB_EPORTERR IF the porting layer returned an error.
+ */
+eMBErrorCode    eMBInit( eMBMode eMode, UCHAR ucSlaveAddress,
+                         UCHAR ucPort, ULONG ulBaudRate, eMBParity eParity );
+
+/*! \ingroup modbus
+ * \brief Initialize the Modbus protocol stack for Modbus TCP.
+ *
+ * This function initializes the Modbus TCP Module. Please note that
+ * frame processing is still disabled until eMBEnable( ) is called.
+ *
+ * \param usTCPPort The TCP port to listen on.
+ * \return If the protocol stack has been initialized correctly the function
+ *   returns eMBErrorCode::MB_ENOERR. Otherwise one of the following error
+ *   codes is returned:
+ *    - eMBErrorCode::MB_EINVAL If the slave address was not valid. Valid
+ *        slave addresses are in the range 1 - 247.
+ *    - eMBErrorCode::MB_EPORTERR IF the porting layer returned an error.
+ */
+eMBErrorCode    eMBTCPInit( USHORT usTCPPort );
+
+/*! \ingroup modbus
+ * \brief Release resources used by the protocol stack.
+ *
+ * This function disables the Modbus protocol stack and release all
+ * hardware resources. It must only be called when the protocol stack 
+ * is disabled. 
+ *
+ * \note Note all ports implement this function. A port which wants to 
+ *   get an callback must define the macro MB_PORT_HAS_CLOSE to 1.
+ *
+ * \return If the resources where released it return eMBErrorCode::MB_ENOERR.
+ *   If the protocol stack is not in the disabled state it returns
+ *   eMBErrorCode::MB_EILLSTATE.
+ */
+eMBErrorCode    eMBClose( void );
+
+/*! \ingroup modbus
+ * \brief Enable the Modbus protocol stack.
+ *
+ * This function enables processing of Modbus frames. Enabling the protocol
+ * stack is only possible if it is in the disabled state.
+ *
+ * \return If the protocol stack is now in the state enabled it returns 
+ *   eMBErrorCode::MB_ENOERR. If it was not in the disabled state it 
+ *   return eMBErrorCode::MB_EILLSTATE.
+ */
+eMBErrorCode    eMBEnable( void );
+
+/*! \ingroup modbus
+ * \brief Disable the Modbus protocol stack.
+ *
+ * This function disables processing of Modbus frames.
+ *
+ * \return If the protocol stack has been disabled it returns 
+ *  eMBErrorCode::MB_ENOERR. If it was not in the enabled state it returns
+ *  eMBErrorCode::MB_EILLSTATE.
+ */
+eMBErrorCode    eMBDisable( void );
+
+/*! \ingroup modbus
+ * \brief The main pooling loop of the Modbus protocol stack.
+ *
+ * This function must be called periodically. The timer interval required
+ * is given by the application dependent Modbus slave timeout. Internally the
+ * function calls xMBPortEventGet() and waits for an event from the receiver or
+ * transmitter state machines. 
+ *
+ * \return If the protocol stack is not in the enabled state the function
+ *   returns eMBErrorCode::MB_EILLSTATE. Otherwise it returns 
+ *   eMBErrorCode::MB_ENOERR.
+ */
+eMBErrorCode    eMBPoll( void );
+
+/*! \ingroup modbus
+ * \brief Configure the slave id of the device.
+ *
+ * This function should be called when the Modbus function <em>Report Slave ID</em>
+ * is enabled ( By defining MB_FUNC_OTHER_REP_SLAVEID_ENABLED in mbconfig.h ).
+ *
+ * \param ucSlaveID Values is returned in the <em>Slave ID</em> byte of the
+ *   <em>Report Slave ID</em> response.
+ * \param xIsRunning If TRUE the <em>Run Indicator Status</em> byte is set to 0xFF.
+ *   otherwise the <em>Run Indicator Status</em> is 0x00.
+ * \param pucAdditional Values which should be returned in the <em>Additional</em>
+ *   bytes of the <em> Report Slave ID</em> response.
+ * \param usAdditionalLen Length of the buffer <code>pucAdditonal</code>.
+ *
+ * \return If the static buffer defined by MB_FUNC_OTHER_REP_SLAVEID_BUF in
+ *   mbconfig.h is to small it returns eMBErrorCode::MB_ENORES. Otherwise
+ *   it returns eMBErrorCode::MB_ENOERR.
+ */
+eMBErrorCode    eMBSetSlaveID( UCHAR ucSlaveID, BOOL xIsRunning,
+                               UCHAR const *pucAdditional,
+                               USHORT usAdditionalLen );
+
+/*! \ingroup modbus
+ * \brief Registers a callback handler for a given function code.
+ *
+ * This function registers a new callback handler for a given function code.
+ * The callback handler supplied is responsible for interpreting the Modbus PDU and
+ * the creation of an appropriate response. In case of an error it should return
+ * one of the possible Modbus exceptions which results in a Modbus exception frame
+ * sent by the protocol stack. 
+ *
+ * \param ucFunctionCode The Modbus function code for which this handler should
+ *   be registers. Valid function codes are in the range 1 to 127.
+ * \param pxHandler The function handler which should be called in case
+ *   such a frame is received. If \c NULL a previously registered function handler
+ *   for this function code is removed.
+ *
+ * \return eMBErrorCode::MB_ENOERR if the handler has been installed. If no
+ *   more resources are available it returns eMBErrorCode::MB_ENORES. In this
+ *   case the values in mbconfig.h should be adjusted. If the argument was not
+ *   valid it returns eMBErrorCode::MB_EINVAL.
+ */
+eMBErrorCode    eMBRegisterCB( UCHAR ucFunctionCode, 
+                               pxMBFunctionHandler pxHandler );
+
+/* ----------------------- Callback -----------------------------------------*/
+
+/*! \defgroup modbus_registers Modbus Registers
+ * \code #include "mb.h" \endcode
+ * The protocol stack does not internally allocate any memory for the
+ * registers. This makes the protocol stack very small and also usable on
+ * low end targets. In addition the values don't have to be in the memory
+ * and could for example be stored in a flash.<br>
+ * Whenever the protocol stack requires a value it calls one of the callback
+ * function with the register address and the number of registers to read
+ * as an argument. The application should then read the actual register values
+ * (for example the ADC voltage) and should store the result in the supplied
+ * buffer.<br>
+ * If the protocol stack wants to update a register value because a write
+ * register function was received a buffer with the new register values is
+ * passed to the callback function. The function should then use these values
+ * to update the application register values.
+ */
+
+/*! \ingroup modbus_registers
+ * \brief Callback function used if the value of a <em>Input Register</em>
+ *   is required by the protocol stack. The starting register address is given
+ *   by \c usAddress and the last register is given by <tt>usAddress +
+ *   usNRegs - 1</tt>.
+ *
+ * \param pucRegBuffer A buffer where the callback function should write
+ *   the current value of the modbus registers to.
+ * \param usAddress The starting address of the register. Input registers
+ *   are in the range 1 - 65535.
+ * \param usNRegs Number of registers the callback function must supply.
+ *
+ * \return The function must return one of the following error codes:
+ *   - eMBErrorCode::MB_ENOERR If no error occurred. In this case a normal
+ *       Modbus response is sent.
+ *   - eMBErrorCode::MB_ENOREG If the application can not supply values
+ *       for registers within this range. In this case a 
+ *       <b>ILLEGAL DATA ADDRESS</b> exception frame is sent as a response.
+ *   - eMBErrorCode::MB_ETIMEDOUT If the requested register block is
+ *       currently not available and the application dependent response
+ *       timeout would be violated. In this case a <b>SLAVE DEVICE BUSY</b>
+ *       exception is sent as a response.
+ *   - eMBErrorCode::MB_EIO If an unrecoverable error occurred. In this case
+ *       a <b>SLAVE DEVICE FAILURE</b> exception is sent as a response.
+ */
+eMBErrorCode    eMBRegInputCB( UCHAR * pucRegBuffer, USHORT usAddress,
+                               USHORT usNRegs );
+
+/*! \ingroup modbus_registers
+ * \brief Callback function used if a <em>Holding Register</em> value is
+ *   read or written by the protocol stack. The starting register address
+ *   is given by \c usAddress and the last register is given by
+ *   <tt>usAddress + usNRegs - 1</tt>.
+ *
+ * \param pucRegBuffer If the application registers values should be updated the
+ *   buffer points to the new registers values. If the protocol stack needs
+ *   to now the current values the callback function should write them into
+ *   this buffer.
+ * \param usAddress The starting address of the register.
+ * \param usNRegs Number of registers to read or write.
+ * \param eMode If eMBRegisterMode::MB_REG_WRITE the application register 
+ *   values should be updated from the values in the buffer. For example
+ *   this would be the case when the Modbus master has issued an 
+ *   <b>WRITE SINGLE REGISTER</b> command.
+ *   If the value eMBRegisterMode::MB_REG_READ the application should copy 
+ *   the current values into the buffer \c pucRegBuffer.
+ *
+ * \return The function must return one of the following error codes:
+ *   - eMBErrorCode::MB_ENOERR If no error occurred. In this case a normal
+ *       Modbus response is sent.
+ *   - eMBErrorCode::MB_ENOREG If the application can not supply values
+ *       for registers within this range. In this case a 
+ *       <b>ILLEGAL DATA ADDRESS</b> exception frame is sent as a response.
+ *   - eMBErrorCode::MB_ETIMEDOUT If the requested register block is
+ *       currently not available and the application dependent response
+ *       timeout would be violated. In this case a <b>SLAVE DEVICE BUSY</b>
+ *       exception is sent as a response.
+ *   - eMBErrorCode::MB_EIO If an unrecoverable error occurred. In this case
+ *       a <b>SLAVE DEVICE FAILURE</b> exception is sent as a response.
+ */
+eMBErrorCode    eMBRegHoldingCB( UCHAR * pucRegBuffer, USHORT usAddress,
+                                 USHORT usNRegs, eMBRegisterMode eMode );
+
+/*! \ingroup modbus_registers
+ * \brief Callback function used if a <em>Coil Register</em> value is
+ *   read or written by the protocol stack. If you are going to use
+ *   this function you might use the functions xMBUtilSetBits(  ) and
+ *   xMBUtilGetBits(  ) for working with bitfields.
+ *
+ * \param pucRegBuffer The bits are packed in bytes where the first coil
+ *   starting at address \c usAddress is stored in the LSB of the
+ *   first byte in the buffer <code>pucRegBuffer</code>.
+ *   If the buffer should be written by the callback function unused
+ *   coil values (I.e. if not a multiple of eight coils is used) should be set
+ *   to zero.
+ * \param usAddress The first coil number.
+ * \param usNCoils Number of coil values requested.
+ * \param eMode If eMBRegisterMode::MB_REG_WRITE the application values should
+ *   be updated from the values supplied in the buffer \c pucRegBuffer.
+ *   If eMBRegisterMode::MB_REG_READ the application should store the current
+ *   values in the buffer \c pucRegBuffer.
+ *
+ * \return The function must return one of the following error codes:
+ *   - eMBErrorCode::MB_ENOERR If no error occurred. In this case a normal
+ *       Modbus response is sent.
+ *   - eMBErrorCode::MB_ENOREG If the application does not map an coils
+ *       within the requested address range. In this case a 
+ *       <b>ILLEGAL DATA ADDRESS</b> is sent as a response.
+ *   - eMBErrorCode::MB_ETIMEDOUT If the requested register block is
+ *       currently not available and the application dependent response
+ *       timeout would be violated. In this case a <b>SLAVE DEVICE BUSY</b>
+ *       exception is sent as a response.
+ *   - eMBErrorCode::MB_EIO If an unrecoverable error occurred. In this case
+ *       a <b>SLAVE DEVICE FAILURE</b> exception is sent as a response.
+ */
+eMBErrorCode    eMBRegCoilsCB( UCHAR * pucRegBuffer, USHORT usAddress,
+                               USHORT usNCoils, eMBRegisterMode eMode );
+
+/*! \ingroup modbus_registers
+ * \brief Callback function used if a <em>Input Discrete Register</em> value is
+ *   read by the protocol stack.
+ *
+ * If you are going to use his function you might use the functions
+ * xMBUtilSetBits(  ) and xMBUtilGetBits(  ) for working with bitfields.
+ *
+ * \param pucRegBuffer The buffer should be updated with the current
+ *   coil values. The first discrete input starting at \c usAddress must be
+ *   stored at the LSB of the first byte in the buffer. If the requested number
+ *   is not a multiple of eight the remaining bits should be set to zero.
+ * \param usAddress The starting address of the first discrete input.
+ * \param usNDiscrete Number of discrete input values.
+ * \return The function must return one of the following error codes:
+ *   - eMBErrorCode::MB_ENOERR If no error occurred. In this case a normal
+ *       Modbus response is sent.
+ *   - eMBErrorCode::MB_ENOREG If no such discrete inputs exists.
+ *       In this case a <b>ILLEGAL DATA ADDRESS</b> exception frame is sent 
+ *       as a response.
+ *   - eMBErrorCode::MB_ETIMEDOUT If the requested register block is
+ *       currently not available and the application dependent response
+ *       timeout would be violated. In this case a <b>SLAVE DEVICE BUSY</b>
+ *       exception is sent as a response.
+ *   - eMBErrorCode::MB_EIO If an unrecoverable error occurred. In this case
+ *       a <b>SLAVE DEVICE FAILURE</b> exception is sent as a response.
+ */
+eMBErrorCode    eMBRegDiscreteCB( UCHAR * pucRegBuffer, USHORT usAddress,
+                                  USHORT usNDiscrete );
+
+#ifdef __cplusplus
+PR_END_EXTERN_C
+#endif
+#endif
diff --git a/apps/include/modbus/mbconfig.h b/apps/include/modbus/mbconfig.h
new file mode 100644
index 000000000..21252ae58
--- /dev/null
+++ b/apps/include/modbus/mbconfig.h
@@ -0,0 +1,132 @@
+/* 
+ * FreeModbus Libary: A portable Modbus implementation for Modbus ASCII/RTU.
+ * Copyright (c) 2006 Christian Walter <wolti@sil.at>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * File: $Id: mbconfig.h,v 1.15 2010/06/06 13:54:40 wolti Exp $
+ */
+
+#ifndef _MB_CONFIG_H
+#define _MB_CONFIG_H
+
+#ifdef __cplusplus
+PR_BEGIN_EXTERN_C
+#endif
+/* ----------------------- Defines ------------------------------------------*/
+/*! \defgroup modbus_cfg Modbus Configuration
+ *
+ * Most modules in the protocol stack are completly optional and can be
+ * excluded. This is specially important if target resources are very small
+ * and program memory space should be saved.<br>
+ *
+ * All of these settings are available in the file <code>mbconfig.h</code>
+ */
+/*! \addtogroup modbus_cfg
+ *  @{
+ */
+/*! \brief If Modbus ASCII support is enabled. */
+#define MB_ASCII_ENABLED                        (  1 )
+
+/*! \brief If Modbus RTU support is enabled. */
+#define MB_RTU_ENABLED                          (  1 )
+
+/*! \brief If Modbus TCP support is enabled. */
+#define MB_TCP_ENABLED                          (  0 )
+
+/*! \brief The character timeout value for Modbus ASCII.
+ *
+ * The character timeout value is not fixed for Modbus ASCII and is therefore
+ * a configuration option. It should be set to the maximum expected delay
+ * time of the network.
+ */
+#define MB_ASCII_TIMEOUT_SEC                    (  1 )
+
+/*! \brief Timeout to wait in ASCII prior to enabling transmitter.
+ *
+ * If defined the function calls vMBPortSerialDelay with the argument
+ * MB_ASCII_TIMEOUT_WAIT_BEFORE_SEND_MS to allow for a delay before
+ * the serial transmitter is enabled. This is required because some
+ * targets are so fast that there is no time between receiving and
+ * transmitting the frame. If the master is to slow with enabling its 
+ * receiver then he will not receive the response correctly.
+ */
+#ifndef MB_ASCII_TIMEOUT_WAIT_BEFORE_SEND_MS
+#define MB_ASCII_TIMEOUT_WAIT_BEFORE_SEND_MS    ( 0 )
+#endif
+
+/*! \brief Maximum number of Modbus functions codes the protocol stack
+ *    should support.
+ *
+ * The maximum number of supported Modbus functions must be greater than
+ * the sum of all enabled functions in this file and custom function
+ * handlers. If set to small adding more functions will fail.
+ */
+#define MB_FUNC_HANDLERS_MAX                    ( 16 )
+
+/*! \brief Number of bytes which should be allocated for the <em>Report Slave ID
+ *    </em>command.
+ *
+ * This number limits the maximum size of the additional segment in the
+ * report slave id function. See eMBSetSlaveID(  ) for more information on
+ * how to set this value. It is only used if MB_FUNC_OTHER_REP_SLAVEID_ENABLED
+ * is set to <code>1</code>.
+ */
+#define MB_FUNC_OTHER_REP_SLAVEID_BUF           ( 32 )
+
+/*! \brief If the <em>Report Slave ID</em> function should be enabled. */
+#define MB_FUNC_OTHER_REP_SLAVEID_ENABLED       (  1 )
+
+/*! \brief If the <em>Read Input Registers</em> function should be enabled. */
+#define MB_FUNC_READ_INPUT_ENABLED              (  1 )
+
+/*! \brief If the <em>Read Holding Registers</em> function should be enabled. */
+#define MB_FUNC_READ_HOLDING_ENABLED            (  1 )
+
+/*! \brief If the <em>Write Single Register</em> function should be enabled. */
+#define MB_FUNC_WRITE_HOLDING_ENABLED           (  1 )
+
+/*! \brief If the <em>Write Multiple registers</em> function should be enabled. */
+#define MB_FUNC_WRITE_MULTIPLE_HOLDING_ENABLED  (  1 )
+
+/*! \brief If the <em>Read Coils</em> function should be enabled. */
+#define MB_FUNC_READ_COILS_ENABLED              (  1 )
+
+/*! \brief If the <em>Write Coils</em> function should be enabled. */
+#define MB_FUNC_WRITE_COIL_ENABLED              (  1 )
+
+/*! \brief If the <em>Write Multiple Coils</em> function should be enabled. */
+#define MB_FUNC_WRITE_MULTIPLE_COILS_ENABLED    (  1 )
+
+/*! \brief If the <em>Read Discrete Inputs</em> function should be enabled. */
+#define MB_FUNC_READ_DISCRETE_INPUTS_ENABLED    (  1 )
+
+/*! \brief If the <em>Read/Write Multiple Registers</em> function should be enabled. */
+#define MB_FUNC_READWRITE_HOLDING_ENABLED       (  1 )
+
+/*! @} */
+#ifdef __cplusplus
+    PR_END_EXTERN_C
+#endif
+#endif
diff --git a/apps/include/modbus/mbframe.h b/apps/include/modbus/mbframe.h
new file mode 100644
index 000000000..99d59c613
--- /dev/null
+++ b/apps/include/modbus/mbframe.h
@@ -0,0 +1,87 @@
+/* 
+ * FreeModbus Libary: A portable Modbus implementation for Modbus ASCII/RTU.
+ * Copyright (c) 2006 Christian Walter <wolti@sil.at>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * File: $Id: mbframe.h,v 1.9 2006/12/07 22:10:34 wolti Exp $
+ */
+
+#ifndef _MB_FRAME_H
+#define _MB_FRAME_H
+
+#ifdef __cplusplus
+PR_BEGIN_EXTERN_C
+#endif
+
+/*!
+ * Constants which defines the format of a modbus frame. The example is
+ * shown for a Modbus RTU/ASCII frame. Note that the Modbus PDU is not
+ * dependent on the underlying transport.
+ *
+ * <code>
+ * <------------------------ MODBUS SERIAL LINE PDU (1) ------------------->
+ *              <----------- MODBUS PDU (1') ---------------->
+ *  +-----------+---------------+----------------------------+-------------+
+ *  | Address   | Function Code | Data                       | CRC/LRC     |
+ *  +-----------+---------------+----------------------------+-------------+
+ *  |           |               |                                   |
+ * (2)        (3/2')           (3')                                (4)
+ *
+ * (1)  ... MB_SER_PDU_SIZE_MAX = 256
+ * (2)  ... MB_SER_PDU_ADDR_OFF = 0
+ * (3)  ... MB_SER_PDU_PDU_OFF  = 1
+ * (4)  ... MB_SER_PDU_SIZE_CRC = 2
+ *
+ * (1') ... MB_PDU_SIZE_MAX     = 253
+ * (2') ... MB_PDU_FUNC_OFF     = 0
+ * (3') ... MB_PDU_DATA_OFF     = 1
+ * </code>
+ */
+
+/* ----------------------- Defines ------------------------------------------*/
+#define MB_PDU_SIZE_MAX     253 /*!< Maximum size of a PDU. */
+#define MB_PDU_SIZE_MIN     1   /*!< Function Code */
+#define MB_PDU_FUNC_OFF     0   /*!< Offset of function code in PDU. */
+#define MB_PDU_DATA_OFF     1   /*!< Offset for response data in PDU. */
+
+/* ----------------------- Prototypes  0-------------------------------------*/
+typedef void    ( *pvMBFrameStart ) ( void );
+
+typedef void    ( *pvMBFrameStop ) ( void );
+
+typedef eMBErrorCode( *peMBFrameReceive ) ( UCHAR * pucRcvAddress,
+                                            UCHAR ** pucFrame,
+                                            USHORT * pusLength );
+
+typedef eMBErrorCode( *peMBFrameSend ) ( UCHAR slaveAddress,
+                                         const UCHAR * pucFrame,
+                                         USHORT usLength );
+
+typedef void( *pvMBFrameClose ) ( void );
+
+#ifdef __cplusplus
+PR_END_EXTERN_C
+#endif
+#endif
diff --git a/apps/include/modbus/mbfunc.h b/apps/include/modbus/mbfunc.h
new file mode 100644
index 000000000..aea14f759
--- /dev/null
+++ b/apps/include/modbus/mbfunc.h
@@ -0,0 +1,80 @@
+/* 
+ * FreeModbus Libary: A portable Modbus implementation for Modbus ASCII/RTU.
+ * Copyright (c) 2006 Christian Walter <wolti@sil.at>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * File: $Id: mbfunc.h,v 1.12 2006/12/07 22:10:34 wolti Exp $
+ */
+
+#ifndef _MB_FUNC_H
+#define _MB_FUNC_H
+
+#ifdef __cplusplus
+PR_BEGIN_EXTERN_C
+#endif
+#if MB_FUNC_OTHER_REP_SLAVEID_BUF > 0
+    eMBException eMBFuncReportSlaveID( UCHAR * pucFrame, USHORT * usLen );
+#endif
+
+#if MB_FUNC_READ_INPUT_ENABLED > 0
+eMBException    eMBFuncReadInputRegister( UCHAR * pucFrame, USHORT * usLen );
+#endif
+
+#if MB_FUNC_READ_HOLDING_ENABLED > 0
+eMBException    eMBFuncReadHoldingRegister( UCHAR * pucFrame, USHORT * usLen );
+#endif
+
+#if MB_FUNC_WRITE_HOLDING_ENABLED > 0
+eMBException    eMBFuncWriteHoldingRegister( UCHAR * pucFrame, USHORT * usLen );
+#endif
+
+#if MB_FUNC_WRITE_MULTIPLE_HOLDING_ENABLED > 0
+eMBException    eMBFuncWriteMultipleHoldingRegister( UCHAR * pucFrame, USHORT * usLen );
+#endif
+
+#if MB_FUNC_READ_COILS_ENABLED > 0
+eMBException    eMBFuncReadCoils( UCHAR * pucFrame, USHORT * usLen );
+#endif
+
+#if MB_FUNC_WRITE_COIL_ENABLED > 0
+eMBException    eMBFuncWriteCoil( UCHAR * pucFrame, USHORT * usLen );
+#endif
+
+#if MB_FUNC_WRITE_MULTIPLE_COILS_ENABLED > 0
+eMBException    eMBFuncWriteMultipleCoils( UCHAR * pucFrame, USHORT * usLen );
+#endif
+
+#if MB_FUNC_READ_DISCRETE_INPUTS_ENABLED > 0
+eMBException    eMBFuncReadDiscreteInputs( UCHAR * pucFrame, USHORT * usLen );
+#endif
+
+#if MB_FUNC_READWRITE_HOLDING_ENABLED > 0
+eMBException    eMBFuncReadWriteMultipleHoldingRegister( UCHAR * pucFrame, USHORT * usLen );
+#endif
+
+#ifdef __cplusplus
+PR_END_EXTERN_C
+#endif
+#endif
diff --git a/apps/include/modbus/mbport.h b/apps/include/modbus/mbport.h
new file mode 100644
index 000000000..4f25a9644
--- /dev/null
+++ b/apps/include/modbus/mbport.h
@@ -0,0 +1,129 @@
+/* 
+ * FreeModbus Libary: A portable Modbus implementation for Modbus ASCII/RTU.
+ * Copyright (c) 2006 Christian Walter <wolti@sil.at>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * File: $Id: mbport.h,v 1.19 2010/06/06 13:54:40 wolti Exp $
+ */
+
+#ifndef _MB_PORT_H
+#define _MB_PORT_H
+
+#ifdef __cplusplus
+PR_BEGIN_EXTERN_C
+#endif
+
+/* ----------------------- Type definitions ---------------------------------*/
+
+typedef enum
+{
+    EV_READY,                   /*!< Startup finished. */
+    EV_FRAME_RECEIVED,          /*!< Frame received. */
+    EV_EXECUTE,                 /*!< Execute function. */
+    EV_FRAME_SENT               /*!< Frame sent. */
+} eMBEventType;
+
+/*! \ingroup modbus
+ * \brief Parity used for characters in serial mode.
+ *
+ * The parity which should be applied to the characters sent over the serial
+ * link. Please note that this values are actually passed to the porting
+ * layer and therefore not all parity modes might be available.
+ */
+typedef enum
+{
+    MB_PAR_NONE,                /*!< No parity. */
+    MB_PAR_ODD,                 /*!< Odd parity. */
+    MB_PAR_EVEN                 /*!< Even parity. */
+} eMBParity;
+
+/* ----------------------- Supporting functions -----------------------------*/
+BOOL            xMBPortEventInit( void );
+
+BOOL            xMBPortEventPost( eMBEventType eEvent );
+
+BOOL            xMBPortEventGet(  /*@out@ */ eMBEventType * eEvent );
+
+/* ----------------------- Serial port functions ----------------------------*/
+
+BOOL            xMBPortSerialInit( UCHAR ucPort, ULONG ulBaudRate,
+                                   UCHAR ucDataBits, eMBParity eParity );
+
+void            vMBPortClose( void );
+
+void            xMBPortSerialClose( void );
+
+void            vMBPortSerialEnable( BOOL xRxEnable, BOOL xTxEnable );
+
+BOOL            xMBPortSerialGetByte( CHAR * pucByte );
+
+BOOL            xMBPortSerialPutByte( CHAR ucByte );
+
+/* ----------------------- Timers functions ---------------------------------*/
+BOOL            xMBPortTimersInit( USHORT usTimeOut50us );
+
+void            xMBPortTimersClose( void );
+
+void            vMBPortTimersEnable( void );
+
+void            vMBPortTimersDisable( void );
+
+void            vMBPortTimersDelay( USHORT usTimeOutMS );
+
+/* ----------------------- Callback for the protocol stack ------------------*/
+
+/*!
+ * \brief Callback function for the porting layer when a new byte is
+ *   available.
+ *
+ * Depending upon the mode this callback function is used by the RTU or
+ * ASCII transmission layers. In any case a call to xMBPortSerialGetByte()
+ * must immediately return a new character.
+ *
+ * \return <code>TRUE</code> if a event was posted to the queue because
+ *   a new byte was received. The port implementation should wake up the
+ *   tasks which are currently blocked on the eventqueue.
+ */
+extern          BOOL( *pxMBFrameCBByteReceived ) ( void );
+
+extern          BOOL( *pxMBFrameCBTransmitterEmpty ) ( void );
+
+extern          BOOL( *pxMBPortCBTimerExpired ) ( void );
+
+/* ----------------------- TCP port functions -------------------------------*/
+BOOL            xMBTCPPortInit( USHORT usTCPPort );
+
+void            vMBTCPPortClose( void );
+
+void            vMBTCPPortDisable( void );
+
+BOOL            xMBTCPPortGetRequest( UCHAR **ppucMBTCPFrame, USHORT * usTCPLength );
+
+BOOL            xMBTCPPortSendResponse( const UCHAR *pucMBTCPFrame, USHORT usTCPLength );
+
+#ifdef __cplusplus
+PR_END_EXTERN_C
+#endif
+#endif
diff --git a/apps/include/modbus/mbproto.h b/apps/include/modbus/mbproto.h
new file mode 100644
index 000000000..786aaf403
--- /dev/null
+++ b/apps/include/modbus/mbproto.h
@@ -0,0 +1,83 @@
+/* 
+ * FreeModbus Libary: A portable Modbus implementation for Modbus ASCII/RTU.
+ * Copyright (c) 2006 Christian Walter <wolti@sil.at>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * File: $Id: mbproto.h,v 1.14 2006/12/07 22:10:34 wolti Exp $
+ */
+
+#ifndef _MB_PROTO_H
+#define _MB_PROTO_H
+
+#ifdef __cplusplus
+PR_BEGIN_EXTERN_C
+#endif
+/* ----------------------- Defines ------------------------------------------*/
+#define MB_ADDRESS_BROADCAST    ( 0 )   /*! Modbus broadcast address. */
+#define MB_ADDRESS_MIN          ( 1 )   /*! Smallest possible slave address. */
+#define MB_ADDRESS_MAX          ( 247 ) /*! Biggest possible slave address. */
+#define MB_FUNC_NONE                          (  0 )
+#define MB_FUNC_READ_COILS                    (  1 )
+#define MB_FUNC_READ_DISCRETE_INPUTS          (  2 )
+#define MB_FUNC_WRITE_SINGLE_COIL             (  5 )
+#define MB_FUNC_WRITE_MULTIPLE_COILS          ( 15 )
+#define MB_FUNC_READ_HOLDING_REGISTER         (  3 )
+#define MB_FUNC_READ_INPUT_REGISTER           (  4 )
+#define MB_FUNC_WRITE_REGISTER                (  6 )
+#define MB_FUNC_WRITE_MULTIPLE_REGISTERS      ( 16 )
+#define MB_FUNC_READWRITE_MULTIPLE_REGISTERS  ( 23 )
+#define MB_FUNC_DIAG_READ_EXCEPTION           (  7 )
+#define MB_FUNC_DIAG_DIAGNOSTIC               (  8 )
+#define MB_FUNC_DIAG_GET_COM_EVENT_CNT        ( 11 )
+#define MB_FUNC_DIAG_GET_COM_EVENT_LOG        ( 12 )
+#define MB_FUNC_OTHER_REPORT_SLAVEID          ( 17 )
+#define MB_FUNC_ERROR                         ( 128 )
+/* ----------------------- Type definitions ---------------------------------*/
+    typedef enum
+{
+    MB_EX_NONE = 0x00,
+    MB_EX_ILLEGAL_FUNCTION = 0x01,
+    MB_EX_ILLEGAL_DATA_ADDRESS = 0x02,
+    MB_EX_ILLEGAL_DATA_VALUE = 0x03,
+    MB_EX_SLAVE_DEVICE_FAILURE = 0x04,
+    MB_EX_ACKNOWLEDGE = 0x05,
+    MB_EX_SLAVE_BUSY = 0x06,
+    MB_EX_MEMORY_PARITY_ERROR = 0x08,
+    MB_EX_GATEWAY_PATH_FAILED = 0x0A,
+    MB_EX_GATEWAY_TGT_FAILED = 0x0B
+} eMBException;
+
+typedef         eMBException( *pxMBFunctionHandler ) ( UCHAR * pucFrame, USHORT * pusLength );
+
+typedef struct
+{
+    UCHAR           ucFunctionCode;
+    pxMBFunctionHandler pxHandler;
+} xMBFunctionHandler;
+
+#ifdef __cplusplus
+PR_END_EXTERN_C
+#endif
+#endif
diff --git a/apps/include/modbus/mbutils.h b/apps/include/modbus/mbutils.h
new file mode 100644
index 000000000..61495751d
--- /dev/null
+++ b/apps/include/modbus/mbutils.h
@@ -0,0 +1,108 @@
+/* 
+ * FreeModbus Libary: A portable Modbus implementation for Modbus ASCII/RTU.
+ * Copyright (c) 2006 Christian Walter <wolti@sil.at>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * File: $Id: mbutils.h,v 1.5 2006/12/07 22:10:34 wolti Exp $
+ */
+
+#ifndef _MB_UTILS_H
+#define _MB_UTILS_H
+
+#ifdef __cplusplus
+PR_BEGIN_EXTERN_C
+#endif
+/*! \defgroup modbus_utils Utilities
+ *
+ * This module contains some utility functions which can be used by
+ * the application. It includes some special functions for working with
+ * bitfields backed by a character array buffer.
+ *
+ */
+/*! \addtogroup modbus_utils
+ *  @{
+ */
+/*! \brief Function to set bits in a byte buffer.
+ *
+ * This function allows the efficient use of an array to implement bitfields.
+ * The array used for storing the bits must always be a multiple of two
+ * bytes. Up to eight bits can be set or cleared in one operation.
+ *
+ * \param ucByteBuf A buffer where the bit values are stored. Must be a
+ *   multiple of 2 bytes. No length checking is performed and if
+ *   usBitOffset / 8 is greater than the size of the buffer memory contents
+ *   is overwritten.
+ * \param usBitOffset The starting address of the bits to set. The first
+ *   bit has the offset 0.
+ * \param ucNBits Number of bits to modify. The value must always be smaller
+ *   than 8.
+ * \param ucValues Thew new values for the bits. The value for the first bit
+ *   starting at <code>usBitOffset</code> is the LSB of the value
+ *   <code>ucValues</code>
+ *
+ * \code
+ * ucBits[2] = {0, 0};
+ *
+ * // Set bit 4 to 1 (read: set 1 bit starting at bit offset 4 to value 1)
+ * xMBUtilSetBits( ucBits, 4, 1, 1 );
+ *
+ * // Set bit 7 to 1 and bit 8 to 0.
+ * xMBUtilSetBits( ucBits, 7, 2, 0x01 );
+ *
+ * // Set bits 8 - 11 to 0x05 and bits 12 - 15 to 0x0A;
+ * xMBUtilSetBits( ucBits, 8, 8, 0x5A);
+ * \endcode
+ */
+void            xMBUtilSetBits( UCHAR * ucByteBuf, USHORT usBitOffset,
+                                UCHAR ucNBits, UCHAR ucValues );
+
+/*! \brief Function to read bits in a byte buffer.
+ *
+ * This function is used to extract up bit values from an array. Up to eight
+ * bit values can be extracted in one step.
+ *
+ * \param ucByteBuf A buffer where the bit values are stored.
+ * \param usBitOffset The starting address of the bits to set. The first
+ *   bit has the offset 0.
+ * \param ucNBits Number of bits to modify. The value must always be smaller
+ *   than 8.
+ *
+ * \code
+ * UCHAR ucBits[2] = {0, 0};
+ * UCHAR ucResult;
+ *
+ * // Extract the bits 3 - 10.
+ * ucResult = xMBUtilGetBits( ucBits, 3, 8 );
+ * \endcode
+ */
+UCHAR           xMBUtilGetBits( UCHAR * ucByteBuf, USHORT usBitOffset,
+                                UCHAR ucNBits );
+
+/*! @} */
+
+#ifdef __cplusplus
+PR_END_EXTERN_C
+#endif
+#endif
diff --git a/apps/modbus/README.txt b/apps/modbus/README.txt
new file mode 100644
index 000000000..8ecf3f8db
--- /dev/null
+++ b/apps/modbus/README.txt
@@ -0,0 +1,54 @@
+apps/modbus README
+==================
+
+This directory contains a port of last open source version of freemodbus
+(BSD license).  The code in this directory is a subset of freemodbus version
+1.5.0 (June 6, 2010) that can be downloaded in its entirety from http://developer.berlios.de/project/showfiles.php?group_id=6120.
+
+Directory Structure/Relation to freemodbus-v1.5.0
+-------------------------------------------------
+
+The original freemodbus download consists of several directories.  This
+subset takes only the contents of one directory, modbus/, that implements
+the core modbus logic and integrates that directory into the NuttX build
+system.  The mapping between freemodbus-v1.5.0 and the nuttx directories
+is shown below:
+
+  --------------------------- ----------------------------------------------
+  freemodbus-v1.5.0           Nuttx
+  --------------------------- ----------------------------------------------
+  All top level .txt files    Not included
+  demo/                       Not included.  This directory contains demo
+                              and porting code for a variety of platforms.
+                              The NuttX demo was ported from the the LINUX
+                              demo in this director and can be found at
+                              apps/examples/modbus.
+  doc/                        Note included.  This directory contains Doxygen
+                              support files.
+  modbus/                     Included in its entirety in various locations:
+         ascii                  apps/modbus/ascii
+         functions              apps/modbus/functions
+         include                apps/include/modbus
+         mb.c                   apps/modbus/mb.c
+         rtu                    apps/modbus/rtu
+         tcp                    apps/modbus/tcp
+  tools/                      Note included.  This directory contain Doxygen
+                              tools.
+  --------------------------- ----------------------------------------------
+
+So this directory is equivalent to the freemodbus-v1.5.0/modbus
+directory except that (1) it may include modifications for the integration
+with NuttX and (2) the modbus/include directory was moved to apps/modbus.
+
+The original, unmodified freemodbus-v1.5.0 was checked in as SVN revision
+4937
+
+The other directory here, nuttx/, implements the NuttX modbus interface.
+It derives from the freemodbus-v1.5.0/demo/LINUX/port directory.
+
+Note
+====
+
+The developer of freemodbus, Christian Walter, is still developing Modbus
+libraries, although they are now commercial.  See
+http://www.embedded-solutions.at/ for further information.
diff --git a/apps/modbus/ascii/mbascii.c b/apps/modbus/ascii/mbascii.c
new file mode 100644
index 000000000..c513457ea
--- /dev/null
+++ b/apps/modbus/ascii/mbascii.c
@@ -0,0 +1,486 @@
+/* 
+ * FreeModbus Libary: A portable Modbus implementation for Modbus ASCII/RTU.
+ * Copyright (c) 2006 Christian Walter <wolti@sil.at>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * File: $Id: mbascii.c,v 1.17 2010/06/06 13:47:07 wolti Exp $
+ */
+
+/* ----------------------- System includes ----------------------------------*/
+#include "stdlib.h"
+#include "string.h"
+
+/* ----------------------- Platform includes --------------------------------*/
+#include "port.h"
+
+/* ----------------------- Modbus includes ----------------------------------*/
+#include "mb.h"
+#include "mbconfig.h"
+#include "mbascii.h"
+#include "mbframe.h"
+
+#include "mbcrc.h"
+#include "mbport.h"
+
+#if MB_ASCII_ENABLED > 0
+
+/* ----------------------- Defines ------------------------------------------*/
+#define MB_ASCII_DEFAULT_CR     '\r'    /*!< Default CR character for Modbus ASCII. */
+#define MB_ASCII_DEFAULT_LF     '\n'    /*!< Default LF character for Modbus ASCII. */
+#define MB_SER_PDU_SIZE_MIN     3       /*!< Minimum size of a Modbus ASCII frame. */
+#define MB_SER_PDU_SIZE_MAX     256     /*!< Maximum size of a Modbus ASCII frame. */
+#define MB_SER_PDU_SIZE_LRC     1       /*!< Size of LRC field in PDU. */
+#define MB_SER_PDU_ADDR_OFF     0       /*!< Offset of slave address in Ser-PDU. */
+#define MB_SER_PDU_PDU_OFF      1       /*!< Offset of Modbus-PDU in Ser-PDU. */
+
+/* ----------------------- Type definitions ---------------------------------*/
+typedef enum
+{
+    STATE_RX_IDLE,              /*!< Receiver is in idle state. */
+    STATE_RX_RCV,               /*!< Frame is beeing received. */
+    STATE_RX_WAIT_EOF           /*!< Wait for End of Frame. */
+} eMBRcvState;
+
+typedef enum
+{
+    STATE_TX_IDLE,              /*!< Transmitter is in idle state. */
+    STATE_TX_START,             /*!< Starting transmission (':' sent). */
+    STATE_TX_DATA,              /*!< Sending of data (Address, Data, LRC). */
+    STATE_TX_END,               /*!< End of transmission. */
+    STATE_TX_NOTIFY             /*!< Notify sender that the frame has been sent. */
+} eMBSndState;
+
+typedef enum
+{
+    BYTE_HIGH_NIBBLE,           /*!< Character for high nibble of byte. */
+    BYTE_LOW_NIBBLE             /*!< Character for low nibble of byte. */
+} eMBBytePos;
+
+/* ----------------------- Static functions ---------------------------------*/
+static UCHAR    prvucMBCHAR2BIN( UCHAR ucCharacter );
+
+static UCHAR    prvucMBBIN2CHAR( UCHAR ucByte );
+
+static UCHAR    prvucMBLRC( UCHAR * pucFrame, USHORT usLen );
+
+/* ----------------------- Static variables ---------------------------------*/
+static volatile eMBSndState eSndState;
+static volatile eMBRcvState eRcvState;
+
+/* We reuse the Modbus RTU buffer because only one buffer is needed and the
+ * RTU buffer is bigger. */
+extern volatile UCHAR ucRTUBuf[];
+static volatile UCHAR *ucASCIIBuf = ucRTUBuf;
+
+static volatile USHORT usRcvBufferPos;
+static volatile eMBBytePos eBytePos;
+
+static volatile UCHAR *pucSndBufferCur;
+static volatile USHORT usSndBufferCount;
+
+static volatile UCHAR ucLRC;
+static volatile UCHAR ucMBLFCharacter;
+
+/* ----------------------- Start implementation -----------------------------*/
+eMBErrorCode
+eMBASCIIInit( UCHAR ucSlaveAddress, UCHAR ucPort, ULONG ulBaudRate, eMBParity eParity )
+{
+    eMBErrorCode    eStatus = MB_ENOERR;
+    ( void )ucSlaveAddress;
+    
+    ENTER_CRITICAL_SECTION(  );
+    ucMBLFCharacter = MB_ASCII_DEFAULT_LF;
+
+    if( xMBPortSerialInit( ucPort, ulBaudRate, 7, eParity ) != TRUE )
+    {
+        eStatus = MB_EPORTERR;
+    }
+    else if( xMBPortTimersInit( MB_ASCII_TIMEOUT_SEC * 20000UL ) != TRUE )
+    {
+        eStatus = MB_EPORTERR;
+    }
+
+    EXIT_CRITICAL_SECTION(  );
+
+    return eStatus;
+}
+
+void
+eMBASCIIStart( void )
+{
+    ENTER_CRITICAL_SECTION(  );
+    vMBPortSerialEnable( TRUE, FALSE );
+    eRcvState = STATE_RX_IDLE;
+    EXIT_CRITICAL_SECTION(  );
+
+    /* No special startup required for ASCII. */
+    ( void )xMBPortEventPost( EV_READY );
+}
+
+void
+eMBASCIIStop( void )
+{
+    ENTER_CRITICAL_SECTION(  );
+    vMBPortSerialEnable( FALSE, FALSE );
+    vMBPortTimersDisable(  );
+    EXIT_CRITICAL_SECTION(  );
+}
+
+eMBErrorCode
+eMBASCIIReceive( UCHAR * pucRcvAddress, UCHAR ** pucFrame, USHORT * pusLength )
+{
+    eMBErrorCode    eStatus = MB_ENOERR;
+
+    ENTER_CRITICAL_SECTION(  );
+    assert( usRcvBufferPos < MB_SER_PDU_SIZE_MAX );
+
+    /* Length and CRC check */
+    if( ( usRcvBufferPos >= MB_SER_PDU_SIZE_MIN )
+        && ( prvucMBLRC( ( UCHAR * ) ucASCIIBuf, usRcvBufferPos ) == 0 ) )
+    {
+        /* Save the address field. All frames are passed to the upper layed
+         * and the decision if a frame is used is done there.
+         */
+        *pucRcvAddress = ucASCIIBuf[MB_SER_PDU_ADDR_OFF];
+
+        /* Total length of Modbus-PDU is Modbus-Serial-Line-PDU minus
+         * size of address field and CRC checksum.
+         */
+        *pusLength = ( USHORT )( usRcvBufferPos - MB_SER_PDU_PDU_OFF - MB_SER_PDU_SIZE_LRC );
+
+        /* Return the start of the Modbus PDU to the caller. */
+        *pucFrame = ( UCHAR * ) & ucASCIIBuf[MB_SER_PDU_PDU_OFF];
+    }
+    else
+    {
+        eStatus = MB_EIO;
+    }
+    EXIT_CRITICAL_SECTION(  );
+    return eStatus;
+}
+
+eMBErrorCode
+eMBASCIISend( UCHAR ucSlaveAddress, const UCHAR * pucFrame, USHORT usLength )
+{
+    eMBErrorCode    eStatus = MB_ENOERR;
+    UCHAR           usLRC;
+
+    ENTER_CRITICAL_SECTION(  );
+    /* Check if the receiver is still in idle state. If not we where too
+     * slow with processing the received frame and the master sent another
+     * frame on the network. We have to abort sending the frame.
+     */
+    if( eRcvState == STATE_RX_IDLE )
+    {
+        /* First byte before the Modbus-PDU is the slave address. */
+        pucSndBufferCur = ( UCHAR * ) pucFrame - 1;
+        usSndBufferCount = 1;
+
+        /* Now copy the Modbus-PDU into the Modbus-Serial-Line-PDU. */
+        pucSndBufferCur[MB_SER_PDU_ADDR_OFF] = ucSlaveAddress;
+        usSndBufferCount += usLength;
+
+        /* Calculate LRC checksum for Modbus-Serial-Line-PDU. */
+        usLRC = prvucMBLRC( ( UCHAR * ) pucSndBufferCur, usSndBufferCount );
+        ucASCIIBuf[usSndBufferCount++] = usLRC;
+
+        /* Activate the transmitter. */
+        eSndState = STATE_TX_START;
+        vMBPortSerialEnable( FALSE, TRUE );
+    }
+    else
+    {
+        eStatus = MB_EIO;
+    }
+    EXIT_CRITICAL_SECTION(  );
+    return eStatus;
+}
+
+BOOL
+xMBASCIIReceiveFSM( void )
+{
+    BOOL            xNeedPoll = FALSE;
+    UCHAR           ucByte;
+    UCHAR           ucResult;
+
+    assert( eSndState == STATE_TX_IDLE );
+
+    ( void )xMBPortSerialGetByte( ( CHAR * ) & ucByte );
+    switch ( eRcvState )
+    {
+        /* A new character is received. If the character is a ':' the input
+         * buffer is cleared. A CR-character signals the end of the data
+         * block. Other characters are part of the data block and their
+         * ASCII value is converted back to a binary representation.
+         */
+    case STATE_RX_RCV:
+        /* Enable timer for character timeout. */
+        vMBPortTimersEnable(  );
+        if( ucByte == ':' )
+        {
+            /* Empty receive buffer. */
+            eBytePos = BYTE_HIGH_NIBBLE;
+            usRcvBufferPos = 0;
+        }
+        else if( ucByte == MB_ASCII_DEFAULT_CR )
+        {
+            eRcvState = STATE_RX_WAIT_EOF;
+        }
+        else
+        {
+            ucResult = prvucMBCHAR2BIN( ucByte );
+            switch ( eBytePos )
+            {
+                /* High nibble of the byte comes first. We check for
+                 * a buffer overflow here. */
+            case BYTE_HIGH_NIBBLE:
+                if( usRcvBufferPos < MB_SER_PDU_SIZE_MAX )
+                {
+                    ucASCIIBuf[usRcvBufferPos] = ( UCHAR )( ucResult << 4 );
+                    eBytePos = BYTE_LOW_NIBBLE;
+                    break;
+                }
+                else
+                {
+                    /* not handled in Modbus specification but seems
+                     * a resonable implementation. */
+                    eRcvState = STATE_RX_IDLE;
+                    /* Disable previously activated timer because of error state. */
+                    vMBPortTimersDisable(  );
+                }
+                break;
+
+            case BYTE_LOW_NIBBLE:
+                ucASCIIBuf[usRcvBufferPos] |= ucResult;
+                usRcvBufferPos++;
+                eBytePos = BYTE_HIGH_NIBBLE;
+                break;
+            }
+        }
+        break;
+
+    case STATE_RX_WAIT_EOF:
+        if( ucByte == ucMBLFCharacter )
+        {
+            /* Disable character timeout timer because all characters are
+             * received. */
+            vMBPortTimersDisable(  );
+            /* Receiver is again in idle state. */
+            eRcvState = STATE_RX_IDLE;
+
+            /* Notify the caller of eMBASCIIReceive that a new frame
+             * was received. */
+            xNeedPoll = xMBPortEventPost( EV_FRAME_RECEIVED );
+        }
+        else if( ucByte == ':' )
+        {
+            /* Empty receive buffer and back to receive state. */
+            eBytePos = BYTE_HIGH_NIBBLE;
+            usRcvBufferPos = 0;
+            eRcvState = STATE_RX_RCV;
+
+            /* Enable timer for character timeout. */
+            vMBPortTimersEnable(  );
+        }
+        else
+        {
+            /* Frame is not okay. Delete entire frame. */
+            eRcvState = STATE_RX_IDLE;
+        }
+        break;
+
+    case STATE_RX_IDLE:
+        if( ucByte == ':' )
+        {
+            /* Enable timer for character timeout. */
+            vMBPortTimersEnable(  );
+            /* Reset the input buffers to store the frame. */
+            usRcvBufferPos = 0;;
+            eBytePos = BYTE_HIGH_NIBBLE;
+            eRcvState = STATE_RX_RCV;
+        }
+        break;
+    }
+
+    return xNeedPoll;
+}
+
+BOOL
+xMBASCIITransmitFSM( void )
+{
+    BOOL            xNeedPoll = FALSE;
+    UCHAR           ucByte;
+
+    assert( eRcvState == STATE_RX_IDLE );
+    switch ( eSndState )
+    {
+        /* Start of transmission. The start of a frame is defined by sending
+         * the character ':'. */
+    case STATE_TX_START:
+        ucByte = ':';
+        xMBPortSerialPutByte( ( CHAR )ucByte );
+        eSndState = STATE_TX_DATA;
+        eBytePos = BYTE_HIGH_NIBBLE;
+        break;
+
+        /* Send the data block. Each data byte is encoded as a character hex
+         * stream with the high nibble sent first and the low nibble sent
+         * last. If all data bytes are exhausted we send a '\r' character
+         * to end the transmission. */
+    case STATE_TX_DATA:
+        if( usSndBufferCount > 0 )
+        {
+            switch ( eBytePos )
+            {
+            case BYTE_HIGH_NIBBLE:
+                ucByte = prvucMBBIN2CHAR( ( UCHAR )( *pucSndBufferCur >> 4 ) );
+                xMBPortSerialPutByte( ( CHAR ) ucByte );
+                eBytePos = BYTE_LOW_NIBBLE;
+                break;
+
+            case BYTE_LOW_NIBBLE:
+                ucByte = prvucMBBIN2CHAR( ( UCHAR )( *pucSndBufferCur & 0x0F ) );
+                xMBPortSerialPutByte( ( CHAR )ucByte );
+                pucSndBufferCur++;
+                eBytePos = BYTE_HIGH_NIBBLE;
+                usSndBufferCount--;
+                break;
+            }
+        }
+        else
+        {
+            xMBPortSerialPutByte( MB_ASCII_DEFAULT_CR );
+            eSndState = STATE_TX_END;
+        }
+        break;
+
+        /* Finish the frame by sending a LF character. */
+    case STATE_TX_END:
+        xMBPortSerialPutByte( ( CHAR )ucMBLFCharacter );
+        /* We need another state to make sure that the CR character has
+         * been sent. */
+        eSndState = STATE_TX_NOTIFY;
+        break;
+
+        /* Notify the task which called eMBASCIISend that the frame has
+         * been sent. */
+    case STATE_TX_NOTIFY:
+        eSndState = STATE_TX_IDLE;
+        xNeedPoll = xMBPortEventPost( EV_FRAME_SENT );
+
+        /* Disable transmitter. This prevents another transmit buffer
+         * empty interrupt. */
+        vMBPortSerialEnable( TRUE, FALSE );
+        eSndState = STATE_TX_IDLE;
+        break;
+
+        /* We should not get a transmitter event if the transmitter is in
+         * idle state.  */
+    case STATE_TX_IDLE:
+        /* enable receiver/disable transmitter. */
+        vMBPortSerialEnable( TRUE, FALSE );
+        break;
+    }
+
+    return xNeedPoll;
+}
+
+BOOL
+xMBASCIITimerT1SExpired( void )
+{
+    switch ( eRcvState )
+    {
+        /* If we have a timeout we go back to the idle state and wait for
+         * the next frame.
+         */
+    case STATE_RX_RCV:
+    case STATE_RX_WAIT_EOF:
+        eRcvState = STATE_RX_IDLE;
+        break;
+
+    default:
+        assert( ( eRcvState == STATE_RX_RCV ) || ( eRcvState == STATE_RX_WAIT_EOF ) );
+        break;
+    }
+    vMBPortTimersDisable(  );
+
+    /* no context switch required. */
+    return FALSE;
+}
+
+
+static          UCHAR
+prvucMBCHAR2BIN( UCHAR ucCharacter )
+{
+    if( ( ucCharacter >= '0' ) && ( ucCharacter <= '9' ) )
+    {
+        return ( UCHAR )( ucCharacter - '0' );
+    }
+    else if( ( ucCharacter >= 'A' ) && ( ucCharacter <= 'F' ) )
+    {
+        return ( UCHAR )( ucCharacter - 'A' + 0x0A );
+    }
+    else
+    {
+        return 0xFF;
+    }
+}
+
+static          UCHAR
+prvucMBBIN2CHAR( UCHAR ucByte )
+{
+    if( ucByte <= 0x09 )
+    {
+        return ( UCHAR )( '0' + ucByte );
+    }
+    else if( ( ucByte >= 0x0A ) && ( ucByte <= 0x0F ) )
+    {
+        return ( UCHAR )( ucByte - 0x0A + 'A' );
+    }
+    else
+    {
+        /* Programming error. */
+        assert( 0 );
+    }
+    return '0';
+}
+
+
+static          UCHAR
+prvucMBLRC( UCHAR * pucFrame, USHORT usLen )
+{
+    UCHAR           ucLRC = 0;  /* LRC char initialized */
+
+    while( usLen-- )
+    {
+        ucLRC += *pucFrame++;   /* Add buffer byte without carry */
+    }
+
+    /* Return twos complement */
+    ucLRC = ( UCHAR ) ( -( ( CHAR ) ucLRC ) );
+    return ucLRC;
+}
+
+#endif
diff --git a/apps/modbus/ascii/mbascii.h b/apps/modbus/ascii/mbascii.h
new file mode 100644
index 000000000..47846ddec
--- /dev/null
+++ b/apps/modbus/ascii/mbascii.h
@@ -0,0 +1,56 @@
+/* 
+ * FreeModbus Libary: A portable Modbus implementation for Modbus ASCII/RTU.
+ * Copyright (c) 2006 Christian Walter <wolti@sil.at>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * File: $Id: mbascii.h,v 1.8 2006/12/07 22:10:34 wolti Exp $
+ */
+
+#ifndef _MB_ASCII_H
+#define _MB_ASCII_H
+
+#ifdef __cplusplus
+PR_BEGIN_EXTERN_C
+#endif
+
+#if MB_ASCII_ENABLED > 0
+eMBErrorCode    eMBASCIIInit( UCHAR slaveAddress, UCHAR ucPort,
+                              ULONG ulBaudRate, eMBParity eParity );
+void            eMBASCIIStart( void );
+void            eMBASCIIStop( void );
+
+eMBErrorCode    eMBASCIIReceive( UCHAR * pucRcvAddress, UCHAR ** pucFrame,
+                                 USHORT * pusLength );
+eMBErrorCode    eMBASCIISend( UCHAR slaveAddress, const UCHAR * pucFrame,
+                              USHORT usLength );
+BOOL            xMBASCIIReceiveFSM( void );
+BOOL            xMBASCIITransmitFSM( void );
+BOOL            xMBASCIITimerT1SExpired( void );
+#endif
+
+#ifdef __cplusplus
+PR_END_EXTERN_C
+#endif
+#endif
diff --git a/apps/modbus/functions/mbfunccoils.c b/apps/modbus/functions/mbfunccoils.c
new file mode 100644
index 000000000..54227b335
--- /dev/null
+++ b/apps/modbus/functions/mbfunccoils.c
@@ -0,0 +1,270 @@
+/* 
+ * FreeModbus Libary: A portable Modbus implementation for Modbus ASCII/RTU.
+ * Copyright (c) 2006 Christian Walter <wolti@sil.at>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * File: $Id: mbfunccoils.c,v 1.8 2007/02/18 23:47:16 wolti Exp $
+ */
+
+/* ----------------------- System includes ----------------------------------*/
+#include "stdlib.h"
+#include "string.h"
+
+/* ----------------------- Platform includes --------------------------------*/
+#include "port.h"
+
+/* ----------------------- Modbus includes ----------------------------------*/
+#include "mb.h"
+#include "mbframe.h"
+#include "mbproto.h"
+#include "mbconfig.h"
+
+/* ----------------------- Defines ------------------------------------------*/
+#define MB_PDU_FUNC_READ_ADDR_OFF           ( MB_PDU_DATA_OFF )
+#define MB_PDU_FUNC_READ_COILCNT_OFF        ( MB_PDU_DATA_OFF + 2 )
+#define MB_PDU_FUNC_READ_SIZE               ( 4 )
+#define MB_PDU_FUNC_READ_COILCNT_MAX        ( 0x07D0 )
+
+#define MB_PDU_FUNC_WRITE_ADDR_OFF          ( MB_PDU_DATA_OFF )
+#define MB_PDU_FUNC_WRITE_VALUE_OFF         ( MB_PDU_DATA_OFF + 2 )
+#define MB_PDU_FUNC_WRITE_SIZE              ( 4 )
+
+#define MB_PDU_FUNC_WRITE_MUL_ADDR_OFF      ( MB_PDU_DATA_OFF )
+#define MB_PDU_FUNC_WRITE_MUL_COILCNT_OFF   ( MB_PDU_DATA_OFF + 2 )
+#define MB_PDU_FUNC_WRITE_MUL_BYTECNT_OFF   ( MB_PDU_DATA_OFF + 4 )
+#define MB_PDU_FUNC_WRITE_MUL_VALUES_OFF    ( MB_PDU_DATA_OFF + 5 )
+#define MB_PDU_FUNC_WRITE_MUL_SIZE_MIN      ( 5 )
+#define MB_PDU_FUNC_WRITE_MUL_COILCNT_MAX   ( 0x07B0 )
+
+/* ----------------------- Static functions ---------------------------------*/
+eMBException    prveMBError2Exception( eMBErrorCode eErrorCode );
+
+/* ----------------------- Start implementation -----------------------------*/
+
+#if MB_FUNC_READ_COILS_ENABLED > 0
+
+eMBException
+eMBFuncReadCoils( UCHAR * pucFrame, USHORT * usLen )
+{
+    USHORT          usRegAddress;
+    USHORT          usCoilCount;
+    UCHAR           ucNBytes;
+    UCHAR          *pucFrameCur;
+
+    eMBException    eStatus = MB_EX_NONE;
+    eMBErrorCode    eRegStatus;
+
+    if( *usLen == ( MB_PDU_FUNC_READ_SIZE + MB_PDU_SIZE_MIN ) )
+    {
+        usRegAddress = ( USHORT )( pucFrame[MB_PDU_FUNC_READ_ADDR_OFF] << 8 );
+        usRegAddress |= ( USHORT )( pucFrame[MB_PDU_FUNC_READ_ADDR_OFF + 1] );
+        usRegAddress++;
+
+        usCoilCount = ( USHORT )( pucFrame[MB_PDU_FUNC_READ_COILCNT_OFF] << 8 );
+        usCoilCount |= ( USHORT )( pucFrame[MB_PDU_FUNC_READ_COILCNT_OFF + 1] );
+
+        /* Check if the number of registers to read is valid. If not
+         * return Modbus illegal data value exception. 
+         */
+        if( ( usCoilCount >= 1 ) &&
+            ( usCoilCount < MB_PDU_FUNC_READ_COILCNT_MAX ) )
+        {
+            /* Set the current PDU data pointer to the beginning. */
+            pucFrameCur = &pucFrame[MB_PDU_FUNC_OFF];
+            *usLen = MB_PDU_FUNC_OFF;
+
+            /* First byte contains the function code. */
+            *pucFrameCur++ = MB_FUNC_READ_COILS;
+            *usLen += 1;
+
+            /* Test if the quantity of coils is a multiple of 8. If not last
+             * byte is only partially field with unused coils set to zero. */
+            if( ( usCoilCount & 0x0007 ) != 0 )
+            {
+                ucNBytes = ( UCHAR )( usCoilCount / 8 + 1 );
+            }
+            else
+            {
+                ucNBytes = ( UCHAR )( usCoilCount / 8 );
+            }
+            *pucFrameCur++ = ucNBytes;
+            *usLen += 1;
+
+            eRegStatus =
+                eMBRegCoilsCB( pucFrameCur, usRegAddress, usCoilCount,
+                               MB_REG_READ );
+
+            /* If an error occured convert it into a Modbus exception. */
+            if( eRegStatus != MB_ENOERR )
+            {
+                eStatus = prveMBError2Exception( eRegStatus );
+            }
+            else
+            {
+                /* The response contains the function code, the starting address
+                 * and the quantity of registers. We reuse the old values in the 
+                 * buffer because they are still valid. */
+                *usLen += ucNBytes;;
+            }
+        }
+        else
+        {
+            eStatus = MB_EX_ILLEGAL_DATA_VALUE;
+        }
+    }
+    else
+    {
+        /* Can't be a valid read coil register request because the length
+         * is incorrect. */
+        eStatus = MB_EX_ILLEGAL_DATA_VALUE;
+    }
+    return eStatus;
+}
+
+#if MB_FUNC_WRITE_COIL_ENABLED > 0
+eMBException
+eMBFuncWriteCoil( UCHAR * pucFrame, USHORT * usLen )
+{
+    USHORT          usRegAddress;
+    UCHAR           ucBuf[2];
+
+    eMBException    eStatus = MB_EX_NONE;
+    eMBErrorCode    eRegStatus;
+
+    if( *usLen == ( MB_PDU_FUNC_WRITE_SIZE + MB_PDU_SIZE_MIN ) )
+    {
+        usRegAddress = ( USHORT )( pucFrame[MB_PDU_FUNC_WRITE_ADDR_OFF] << 8 );
+        usRegAddress |= ( USHORT )( pucFrame[MB_PDU_FUNC_WRITE_ADDR_OFF + 1] );
+        usRegAddress++;
+
+        if( ( pucFrame[MB_PDU_FUNC_WRITE_VALUE_OFF + 1] == 0x00 ) &&
+            ( ( pucFrame[MB_PDU_FUNC_WRITE_VALUE_OFF] == 0xFF ) ||
+              ( pucFrame[MB_PDU_FUNC_WRITE_VALUE_OFF] == 0x00 ) ) )
+        {
+            ucBuf[1] = 0;
+            if( pucFrame[MB_PDU_FUNC_WRITE_VALUE_OFF] == 0xFF )
+            {
+                ucBuf[0] = 1;
+            }
+            else
+            {
+                ucBuf[0] = 0;
+            }
+            eRegStatus =
+                eMBRegCoilsCB( &ucBuf[0], usRegAddress, 1, MB_REG_WRITE );
+
+            /* If an error occured convert it into a Modbus exception. */
+            if( eRegStatus != MB_ENOERR )
+            {
+                eStatus = prveMBError2Exception( eRegStatus );
+            }
+        }
+        else
+        {
+            eStatus = MB_EX_ILLEGAL_DATA_VALUE;
+        }
+    }
+    else
+    {
+        /* Can't be a valid write coil register request because the length
+         * is incorrect. */
+        eStatus = MB_EX_ILLEGAL_DATA_VALUE;
+    }
+    return eStatus;
+}
+
+#endif
+
+#if MB_FUNC_WRITE_MULTIPLE_COILS_ENABLED > 0
+eMBException
+eMBFuncWriteMultipleCoils( UCHAR * pucFrame, USHORT * usLen )
+{
+    USHORT          usRegAddress;
+    USHORT          usCoilCnt;
+    UCHAR           ucByteCount;
+    UCHAR           ucByteCountVerify;
+
+    eMBException    eStatus = MB_EX_NONE;
+    eMBErrorCode    eRegStatus;
+
+    if( *usLen > ( MB_PDU_FUNC_WRITE_SIZE + MB_PDU_SIZE_MIN ) )
+    {
+        usRegAddress = ( USHORT )( pucFrame[MB_PDU_FUNC_WRITE_MUL_ADDR_OFF] << 8 );
+        usRegAddress |= ( USHORT )( pucFrame[MB_PDU_FUNC_WRITE_MUL_ADDR_OFF + 1] );
+        usRegAddress++;
+
+        usCoilCnt = ( USHORT )( pucFrame[MB_PDU_FUNC_WRITE_MUL_COILCNT_OFF] << 8 );
+        usCoilCnt |= ( USHORT )( pucFrame[MB_PDU_FUNC_WRITE_MUL_COILCNT_OFF + 1] );
+
+        ucByteCount = pucFrame[MB_PDU_FUNC_WRITE_MUL_BYTECNT_OFF];
+
+        /* Compute the number of expected bytes in the request. */
+        if( ( usCoilCnt & 0x0007 ) != 0 )
+        {
+            ucByteCountVerify = ( UCHAR )( usCoilCnt / 8 + 1 );
+        }
+        else
+        {
+            ucByteCountVerify = ( UCHAR )( usCoilCnt / 8 );
+        }
+
+        if( ( usCoilCnt >= 1 ) &&
+            ( usCoilCnt <= MB_PDU_FUNC_WRITE_MUL_COILCNT_MAX ) &&
+            ( ucByteCountVerify == ucByteCount ) )
+        {
+            eRegStatus =
+                eMBRegCoilsCB( &pucFrame[MB_PDU_FUNC_WRITE_MUL_VALUES_OFF],
+                               usRegAddress, usCoilCnt, MB_REG_WRITE );
+
+            /* If an error occured convert it into a Modbus exception. */
+            if( eRegStatus != MB_ENOERR )
+            {
+                eStatus = prveMBError2Exception( eRegStatus );
+            }
+            else
+            {
+                /* The response contains the function code, the starting address
+                 * and the quantity of registers. We reuse the old values in the 
+                 * buffer because they are still valid. */
+                *usLen = MB_PDU_FUNC_WRITE_MUL_BYTECNT_OFF;
+            }
+        }
+        else
+        {
+            eStatus = MB_EX_ILLEGAL_DATA_VALUE;
+        }
+    }
+    else
+    {
+        /* Can't be a valid write coil register request because the length
+         * is incorrect. */
+        eStatus = MB_EX_ILLEGAL_DATA_VALUE;
+    }
+    return eStatus;
+}
+
+#endif
+
+#endif
diff --git a/apps/modbus/functions/mbfuncdiag.c b/apps/modbus/functions/mbfuncdiag.c
new file mode 100644
index 000000000..d75ffc0f7
--- /dev/null
+++ b/apps/modbus/functions/mbfuncdiag.c
@@ -0,0 +1,29 @@
+/* 
+ * FreeModbus Libary: A portable Modbus implementation for Modbus ASCII/RTU.
+ * Copyright (c) 2006 Christian Walter <wolti@sil.at>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * File: $Id: mbfuncdiag.c,v 1.3 2006/12/07 22:10:34 wolti Exp $
+ */
diff --git a/apps/modbus/functions/mbfuncdisc.c b/apps/modbus/functions/mbfuncdisc.c
new file mode 100644
index 000000000..fb378441b
--- /dev/null
+++ b/apps/modbus/functions/mbfuncdisc.c
@@ -0,0 +1,125 @@
+ /*
+  * FreeRTOS Modbus Libary: A Modbus serial implementation for FreeRTOS
+  * Copyright (C) 2006 Christian Walter <wolti@sil.at>
+  *
+  * This library is free software; you can redistribute it and/or
+  * modify it under the terms of the GNU Lesser General Public
+  * License as published by the Free Software Foundation; either
+  * version 2.1 of the License, or (at your option) any later version.
+  *
+  * This library is distributed in the hope that it will be useful,
+  * but WITHOUT ANY WARRANTY; without even the implied warranty of
+  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+  * Lesser General Public License for more details.
+  *
+  * You should have received a copy of the GNU Lesser General Public
+  * License along with this library; if not, write to the Free Software
+  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+  */
+
+
+
+/* ----------------------- System includes ----------------------------------*/
+#include "stdlib.h"
+#include "string.h"
+
+/* ----------------------- Platform includes --------------------------------*/
+#include "port.h"
+
+/* ----------------------- Modbus includes ----------------------------------*/
+#include "mb.h"
+#include "mbframe.h"
+#include "mbproto.h"
+#include "mbconfig.h"
+
+/* ----------------------- Defines ------------------------------------------*/
+#define MB_PDU_FUNC_READ_ADDR_OFF           ( MB_PDU_DATA_OFF )
+#define MB_PDU_FUNC_READ_DISCCNT_OFF        ( MB_PDU_DATA_OFF + 2 )
+#define MB_PDU_FUNC_READ_SIZE               ( 4 )
+#define MB_PDU_FUNC_READ_DISCCNT_MAX        ( 0x07D0 )
+
+/* ----------------------- Static functions ---------------------------------*/
+eMBException    prveMBError2Exception( eMBErrorCode eErrorCode );
+
+/* ----------------------- Start implementation -----------------------------*/
+
+#if MB_FUNC_READ_COILS_ENABLED > 0
+
+eMBException
+eMBFuncReadDiscreteInputs( UCHAR * pucFrame, USHORT * usLen )
+{
+    USHORT          usRegAddress;
+    USHORT          usDiscreteCnt;
+    UCHAR           ucNBytes;
+    UCHAR          *pucFrameCur;
+
+    eMBException    eStatus = MB_EX_NONE;
+    eMBErrorCode    eRegStatus;
+
+    if( *usLen == ( MB_PDU_FUNC_READ_SIZE + MB_PDU_SIZE_MIN ) )
+    {
+        usRegAddress = ( USHORT )( pucFrame[MB_PDU_FUNC_READ_ADDR_OFF] << 8 );
+        usRegAddress |= ( USHORT )( pucFrame[MB_PDU_FUNC_READ_ADDR_OFF + 1] );
+        usRegAddress++;
+
+        usDiscreteCnt = ( USHORT )( pucFrame[MB_PDU_FUNC_READ_DISCCNT_OFF] << 8 );
+        usDiscreteCnt |= ( USHORT )( pucFrame[MB_PDU_FUNC_READ_DISCCNT_OFF + 1] );
+
+        /* Check if the number of registers to read is valid. If not
+         * return Modbus illegal data value exception. 
+         */
+        if( ( usDiscreteCnt >= 1 ) &&
+            ( usDiscreteCnt < MB_PDU_FUNC_READ_DISCCNT_MAX ) )
+        {
+            /* Set the current PDU data pointer to the beginning. */
+            pucFrameCur = &pucFrame[MB_PDU_FUNC_OFF];
+            *usLen = MB_PDU_FUNC_OFF;
+
+            /* First byte contains the function code. */
+            *pucFrameCur++ = MB_FUNC_READ_DISCRETE_INPUTS;
+            *usLen += 1;
+
+            /* Test if the quantity of coils is a multiple of 8. If not last
+             * byte is only partially field with unused coils set to zero. */
+            if( ( usDiscreteCnt & 0x0007 ) != 0 )
+            {
+                ucNBytes = ( UCHAR ) ( usDiscreteCnt / 8 + 1 );
+            }
+            else
+            {
+                ucNBytes = ( UCHAR ) ( usDiscreteCnt / 8 );
+            }
+            *pucFrameCur++ = ucNBytes;
+            *usLen += 1;
+
+            eRegStatus =
+                eMBRegDiscreteCB( pucFrameCur, usRegAddress, usDiscreteCnt );
+
+            /* If an error occured convert it into a Modbus exception. */
+            if( eRegStatus != MB_ENOERR )
+            {
+                eStatus = prveMBError2Exception( eRegStatus );
+            }
+            else
+            {
+                /* The response contains the function code, the starting address
+                 * and the quantity of registers. We reuse the old values in the 
+                 * buffer because they are still valid. */
+                *usLen += ucNBytes;;
+            }
+        }
+        else
+        {
+            eStatus = MB_EX_ILLEGAL_DATA_VALUE;
+        }
+    }
+    else
+    {
+        /* Can't be a valid read coil register request because the length
+         * is incorrect. */
+        eStatus = MB_EX_ILLEGAL_DATA_VALUE;
+    }
+    return eStatus;
+}
+
+#endif
diff --git a/apps/modbus/functions/mbfuncholding.c b/apps/modbus/functions/mbfuncholding.c
new file mode 100644
index 000000000..e74a0624d
--- /dev/null
+++ b/apps/modbus/functions/mbfuncholding.c
@@ -0,0 +1,308 @@
+/* 
+ * FreeModbus Libary: A portable Modbus implementation for Modbus ASCII/RTU.
+ * Copyright (c) 2006 Christian Walter <wolti@sil.at>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * File: $Id: mbfuncholding.c,v 1.12 2007/02/18 23:48:22 wolti Exp $
+ */
+
+/* ----------------------- System includes ----------------------------------*/
+#include "stdlib.h"
+#include "string.h"
+
+/* ----------------------- Platform includes --------------------------------*/
+#include "port.h"
+
+/* ----------------------- Modbus includes ----------------------------------*/
+#include "mb.h"
+#include "mbframe.h"
+#include "mbproto.h"
+#include "mbconfig.h"
+
+/* ----------------------- Defines ------------------------------------------*/
+#define MB_PDU_FUNC_READ_ADDR_OFF               ( MB_PDU_DATA_OFF + 0)
+#define MB_PDU_FUNC_READ_REGCNT_OFF             ( MB_PDU_DATA_OFF + 2 )
+#define MB_PDU_FUNC_READ_SIZE                   ( 4 )
+#define MB_PDU_FUNC_READ_REGCNT_MAX             ( 0x007D )
+
+#define MB_PDU_FUNC_WRITE_ADDR_OFF              ( MB_PDU_DATA_OFF + 0)
+#define MB_PDU_FUNC_WRITE_VALUE_OFF             ( MB_PDU_DATA_OFF + 2 )
+#define MB_PDU_FUNC_WRITE_SIZE                  ( 4 )
+
+#define MB_PDU_FUNC_WRITE_MUL_ADDR_OFF          ( MB_PDU_DATA_OFF + 0 )
+#define MB_PDU_FUNC_WRITE_MUL_REGCNT_OFF        ( MB_PDU_DATA_OFF + 2 )
+#define MB_PDU_FUNC_WRITE_MUL_BYTECNT_OFF       ( MB_PDU_DATA_OFF + 4 )
+#define MB_PDU_FUNC_WRITE_MUL_VALUES_OFF        ( MB_PDU_DATA_OFF + 5 )
+#define MB_PDU_FUNC_WRITE_MUL_SIZE_MIN          ( 5 )
+#define MB_PDU_FUNC_WRITE_MUL_REGCNT_MAX        ( 0x0078 )
+
+#define MB_PDU_FUNC_READWRITE_READ_ADDR_OFF     ( MB_PDU_DATA_OFF + 0 )
+#define MB_PDU_FUNC_READWRITE_READ_REGCNT_OFF   ( MB_PDU_DATA_OFF + 2 )
+#define MB_PDU_FUNC_READWRITE_WRITE_ADDR_OFF    ( MB_PDU_DATA_OFF + 4 )
+#define MB_PDU_FUNC_READWRITE_WRITE_REGCNT_OFF  ( MB_PDU_DATA_OFF + 6 )
+#define MB_PDU_FUNC_READWRITE_BYTECNT_OFF       ( MB_PDU_DATA_OFF + 8 )
+#define MB_PDU_FUNC_READWRITE_WRITE_VALUES_OFF  ( MB_PDU_DATA_OFF + 9 )
+#define MB_PDU_FUNC_READWRITE_SIZE_MIN          ( 9 )
+
+/* ----------------------- Static functions ---------------------------------*/
+eMBException    prveMBError2Exception( eMBErrorCode eErrorCode );
+
+/* ----------------------- Start implementation -----------------------------*/
+
+#if MB_FUNC_WRITE_HOLDING_ENABLED > 0
+
+eMBException
+eMBFuncWriteHoldingRegister( UCHAR * pucFrame, USHORT * usLen )
+{
+    USHORT          usRegAddress;
+    eMBException    eStatus = MB_EX_NONE;
+    eMBErrorCode    eRegStatus;
+
+    if( *usLen == ( MB_PDU_FUNC_WRITE_SIZE + MB_PDU_SIZE_MIN ) )
+    {
+        usRegAddress = ( USHORT )( pucFrame[MB_PDU_FUNC_WRITE_ADDR_OFF] << 8 );
+        usRegAddress |= ( USHORT )( pucFrame[MB_PDU_FUNC_WRITE_ADDR_OFF + 1] );
+        usRegAddress++;
+
+        /* Make callback to update the value. */
+        eRegStatus = eMBRegHoldingCB( &pucFrame[MB_PDU_FUNC_WRITE_VALUE_OFF],
+                                      usRegAddress, 1, MB_REG_WRITE );
+
+        /* If an error occured convert it into a Modbus exception. */
+        if( eRegStatus != MB_ENOERR )
+        {
+            eStatus = prveMBError2Exception( eRegStatus );
+        }
+    }
+    else
+    {
+        /* Can't be a valid request because the length is incorrect. */
+        eStatus = MB_EX_ILLEGAL_DATA_VALUE;
+    }
+    return eStatus;
+}
+#endif
+
+#if MB_FUNC_WRITE_MULTIPLE_HOLDING_ENABLED > 0
+eMBException
+eMBFuncWriteMultipleHoldingRegister( UCHAR * pucFrame, USHORT * usLen )
+{
+    USHORT          usRegAddress;
+    USHORT          usRegCount;
+    UCHAR           ucRegByteCount;
+
+    eMBException    eStatus = MB_EX_NONE;
+    eMBErrorCode    eRegStatus;
+
+    if( *usLen >= ( MB_PDU_FUNC_WRITE_MUL_SIZE_MIN + MB_PDU_SIZE_MIN ) )
+    {
+        usRegAddress = ( USHORT )( pucFrame[MB_PDU_FUNC_WRITE_MUL_ADDR_OFF] << 8 );
+        usRegAddress |= ( USHORT )( pucFrame[MB_PDU_FUNC_WRITE_MUL_ADDR_OFF + 1] );
+        usRegAddress++;
+
+        usRegCount = ( USHORT )( pucFrame[MB_PDU_FUNC_WRITE_MUL_REGCNT_OFF] << 8 );
+        usRegCount |= ( USHORT )( pucFrame[MB_PDU_FUNC_WRITE_MUL_REGCNT_OFF + 1] );
+
+        ucRegByteCount = pucFrame[MB_PDU_FUNC_WRITE_MUL_BYTECNT_OFF];
+
+        if( ( usRegCount >= 1 ) &&
+            ( usRegCount <= MB_PDU_FUNC_WRITE_MUL_REGCNT_MAX ) &&
+            ( ucRegByteCount == ( UCHAR ) ( 2 * usRegCount ) ) )
+        {
+            /* Make callback to update the register values. */
+            eRegStatus =
+                eMBRegHoldingCB( &pucFrame[MB_PDU_FUNC_WRITE_MUL_VALUES_OFF],
+                                 usRegAddress, usRegCount, MB_REG_WRITE );
+
+            /* If an error occured convert it into a Modbus exception. */
+            if( eRegStatus != MB_ENOERR )
+            {
+                eStatus = prveMBError2Exception( eRegStatus );
+            }
+            else
+            {
+                /* The response contains the function code, the starting
+                 * address and the quantity of registers. We reuse the
+                 * old values in the buffer because they are still valid.
+                 */
+                *usLen = MB_PDU_FUNC_WRITE_MUL_BYTECNT_OFF;
+            }
+        }
+        else
+        {
+            eStatus = MB_EX_ILLEGAL_DATA_VALUE;
+        }
+    }
+    else
+    {
+        /* Can't be a valid request because the length is incorrect. */
+        eStatus = MB_EX_ILLEGAL_DATA_VALUE;
+    }
+    return eStatus;
+}
+#endif
+
+#if MB_FUNC_READ_HOLDING_ENABLED > 0
+
+eMBException
+eMBFuncReadHoldingRegister( UCHAR * pucFrame, USHORT * usLen )
+{
+    USHORT          usRegAddress;
+    USHORT          usRegCount;
+    UCHAR          *pucFrameCur;
+
+    eMBException    eStatus = MB_EX_NONE;
+    eMBErrorCode    eRegStatus;
+
+    if( *usLen == ( MB_PDU_FUNC_READ_SIZE + MB_PDU_SIZE_MIN ) )
+    {
+        usRegAddress = ( USHORT )( pucFrame[MB_PDU_FUNC_READ_ADDR_OFF] << 8 );
+        usRegAddress |= ( USHORT )( pucFrame[MB_PDU_FUNC_READ_ADDR_OFF + 1] );
+        usRegAddress++;
+
+        usRegCount = ( USHORT )( pucFrame[MB_PDU_FUNC_READ_REGCNT_OFF] << 8 );
+        usRegCount = ( USHORT )( pucFrame[MB_PDU_FUNC_READ_REGCNT_OFF + 1] );
+
+        /* Check if the number of registers to read is valid. If not
+         * return Modbus illegal data value exception. 
+         */
+        if( ( usRegCount >= 1 ) && ( usRegCount <= MB_PDU_FUNC_READ_REGCNT_MAX ) )
+        {
+            /* Set the current PDU data pointer to the beginning. */
+            pucFrameCur = &pucFrame[MB_PDU_FUNC_OFF];
+            *usLen = MB_PDU_FUNC_OFF;
+
+            /* First byte contains the function code. */
+            *pucFrameCur++ = MB_FUNC_READ_HOLDING_REGISTER;
+            *usLen += 1;
+
+            /* Second byte in the response contain the number of bytes. */
+            *pucFrameCur++ = ( UCHAR ) ( usRegCount * 2 );
+            *usLen += 1;
+
+            /* Make callback to fill the buffer. */
+            eRegStatus = eMBRegHoldingCB( pucFrameCur, usRegAddress, usRegCount, MB_REG_READ );
+            /* If an error occured convert it into a Modbus exception. */
+            if( eRegStatus != MB_ENOERR )
+            {
+                eStatus = prveMBError2Exception( eRegStatus );
+            }
+            else
+            {
+                *usLen += usRegCount * 2;
+            }
+        }
+        else
+        {
+            eStatus = MB_EX_ILLEGAL_DATA_VALUE;
+        }
+    }
+    else
+    {
+        /* Can't be a valid request because the length is incorrect. */
+        eStatus = MB_EX_ILLEGAL_DATA_VALUE;
+    }
+    return eStatus;
+}
+
+#endif
+
+#if MB_FUNC_READWRITE_HOLDING_ENABLED > 0
+
+eMBException
+eMBFuncReadWriteMultipleHoldingRegister( UCHAR * pucFrame, USHORT * usLen )
+{
+    USHORT          usRegReadAddress;
+    USHORT          usRegReadCount;
+    USHORT          usRegWriteAddress;
+    USHORT          usRegWriteCount;
+    UCHAR           ucRegWriteByteCount;
+    UCHAR          *pucFrameCur;
+
+    eMBException    eStatus = MB_EX_NONE;
+    eMBErrorCode    eRegStatus;
+
+    if( *usLen >= ( MB_PDU_FUNC_READWRITE_SIZE_MIN + MB_PDU_SIZE_MIN ) )
+    {
+        usRegReadAddress = ( USHORT )( pucFrame[MB_PDU_FUNC_READWRITE_READ_ADDR_OFF] << 8U );
+        usRegReadAddress |= ( USHORT )( pucFrame[MB_PDU_FUNC_READWRITE_READ_ADDR_OFF + 1] );
+        usRegReadAddress++;
+
+        usRegReadCount = ( USHORT )( pucFrame[MB_PDU_FUNC_READWRITE_READ_REGCNT_OFF] << 8U );
+        usRegReadCount |= ( USHORT )( pucFrame[MB_PDU_FUNC_READWRITE_READ_REGCNT_OFF + 1] );
+
+        usRegWriteAddress = ( USHORT )( pucFrame[MB_PDU_FUNC_READWRITE_WRITE_ADDR_OFF] << 8U );
+        usRegWriteAddress |= ( USHORT )( pucFrame[MB_PDU_FUNC_READWRITE_WRITE_ADDR_OFF + 1] );
+        usRegWriteAddress++;
+
+        usRegWriteCount = ( USHORT )( pucFrame[MB_PDU_FUNC_READWRITE_WRITE_REGCNT_OFF] << 8U );
+        usRegWriteCount |= ( USHORT )( pucFrame[MB_PDU_FUNC_READWRITE_WRITE_REGCNT_OFF + 1] );
+
+        ucRegWriteByteCount = pucFrame[MB_PDU_FUNC_READWRITE_BYTECNT_OFF];
+
+        if( ( usRegReadCount >= 1 ) && ( usRegReadCount <= 0x7D ) &&
+            ( usRegWriteCount >= 1 ) && ( usRegWriteCount <= 0x79 ) &&
+            ( ( 2 * usRegWriteCount ) == ucRegWriteByteCount ) )
+        {
+            /* Make callback to update the register values. */
+            eRegStatus = eMBRegHoldingCB( &pucFrame[MB_PDU_FUNC_READWRITE_WRITE_VALUES_OFF],
+                                          usRegWriteAddress, usRegWriteCount, MB_REG_WRITE );
+
+            if( eRegStatus == MB_ENOERR )
+            {
+                /* Set the current PDU data pointer to the beginning. */
+                pucFrameCur = &pucFrame[MB_PDU_FUNC_OFF];
+                *usLen = MB_PDU_FUNC_OFF;
+
+                /* First byte contains the function code. */
+                *pucFrameCur++ = MB_FUNC_READWRITE_MULTIPLE_REGISTERS;
+                *usLen += 1;
+
+                /* Second byte in the response contain the number of bytes. */
+                *pucFrameCur++ = ( UCHAR ) ( usRegReadCount * 2 );
+                *usLen += 1;
+
+                /* Make the read callback. */
+                eRegStatus =
+                    eMBRegHoldingCB( pucFrameCur, usRegReadAddress, usRegReadCount, MB_REG_READ );
+                if( eRegStatus == MB_ENOERR )
+                {
+                    *usLen += 2 * usRegReadCount;
+                }
+            }
+            if( eRegStatus != MB_ENOERR )
+            {
+                eStatus = prveMBError2Exception( eRegStatus );
+            }
+        }
+        else
+        {
+            eStatus = MB_EX_ILLEGAL_DATA_VALUE;
+        }
+    }
+    return eStatus;
+}
+
+#endif
diff --git a/apps/modbus/functions/mbfuncinput.c b/apps/modbus/functions/mbfuncinput.c
new file mode 100644
index 000000000..cceedbafe
--- /dev/null
+++ b/apps/modbus/functions/mbfuncinput.c
@@ -0,0 +1,122 @@
+/* 
+ * FreeModbus Libary: A portable Modbus implementation for Modbus ASCII/RTU.
+ * Copyright (c) 2006 Christian Walter <wolti@sil.at>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * File: $Id: mbfuncinput.c,v 1.10 2007/09/12 10:15:56 wolti Exp $
+ */
+
+/* ----------------------- System includes ----------------------------------*/
+#include "stdlib.h"
+#include "string.h"
+
+/* ----------------------- Platform includes --------------------------------*/
+#include "port.h"
+
+/* ----------------------- Modbus includes ----------------------------------*/
+#include "mb.h"
+#include "mbframe.h"
+#include "mbproto.h"
+#include "mbconfig.h"
+
+/* ----------------------- Defines ------------------------------------------*/
+#define MB_PDU_FUNC_READ_ADDR_OFF           ( MB_PDU_DATA_OFF )
+#define MB_PDU_FUNC_READ_REGCNT_OFF         ( MB_PDU_DATA_OFF + 2 )
+#define MB_PDU_FUNC_READ_SIZE               ( 4 )
+#define MB_PDU_FUNC_READ_REGCNT_MAX         ( 0x007D )
+
+#define MB_PDU_FUNC_READ_RSP_BYTECNT_OFF    ( MB_PDU_DATA_OFF )
+
+/* ----------------------- Static functions ---------------------------------*/
+eMBException    prveMBError2Exception( eMBErrorCode eErrorCode );
+
+/* ----------------------- Start implementation -----------------------------*/
+#if MB_FUNC_READ_INPUT_ENABLED > 0
+
+eMBException
+eMBFuncReadInputRegister( UCHAR * pucFrame, USHORT * usLen )
+{
+    USHORT          usRegAddress;
+    USHORT          usRegCount;
+    UCHAR          *pucFrameCur;
+
+    eMBException    eStatus = MB_EX_NONE;
+    eMBErrorCode    eRegStatus;
+
+    if( *usLen == ( MB_PDU_FUNC_READ_SIZE + MB_PDU_SIZE_MIN ) )
+    {
+        usRegAddress = ( USHORT )( pucFrame[MB_PDU_FUNC_READ_ADDR_OFF] << 8 );
+        usRegAddress |= ( USHORT )( pucFrame[MB_PDU_FUNC_READ_ADDR_OFF + 1] );
+        usRegAddress++;
+
+        usRegCount = ( USHORT )( pucFrame[MB_PDU_FUNC_READ_REGCNT_OFF] << 8 );
+        usRegCount |= ( USHORT )( pucFrame[MB_PDU_FUNC_READ_REGCNT_OFF + 1] );
+
+        /* Check if the number of registers to read is valid. If not
+         * return Modbus illegal data value exception. 
+         */
+        if( ( usRegCount >= 1 )
+            && ( usRegCount < MB_PDU_FUNC_READ_REGCNT_MAX ) )
+        {
+            /* Set the current PDU data pointer to the beginning. */
+            pucFrameCur = &pucFrame[MB_PDU_FUNC_OFF];
+            *usLen = MB_PDU_FUNC_OFF;
+
+            /* First byte contains the function code. */
+            *pucFrameCur++ = MB_FUNC_READ_INPUT_REGISTER;
+            *usLen += 1;
+
+            /* Second byte in the response contain the number of bytes. */
+            *pucFrameCur++ = ( UCHAR )( usRegCount * 2 );
+            *usLen += 1;
+
+            eRegStatus =
+                eMBRegInputCB( pucFrameCur, usRegAddress, usRegCount );
+
+            /* If an error occured convert it into a Modbus exception. */
+            if( eRegStatus != MB_ENOERR )
+            {
+                eStatus = prveMBError2Exception( eRegStatus );
+            }
+            else
+            {
+                *usLen += usRegCount * 2;
+            }
+        }
+        else
+        {
+            eStatus = MB_EX_ILLEGAL_DATA_VALUE;
+        }
+    }
+    else
+    {
+        /* Can't be a valid read input register request because the length
+         * is incorrect. */
+        eStatus = MB_EX_ILLEGAL_DATA_VALUE;
+    }
+    return eStatus;
+}
+
+#endif
diff --git a/apps/modbus/functions/mbfuncother.c b/apps/modbus/functions/mbfuncother.c
new file mode 100644
index 000000000..fcee972bf
--- /dev/null
+++ b/apps/modbus/functions/mbfuncother.c
@@ -0,0 +1,88 @@
+/* 
+ * FreeModbus Libary: A portable Modbus implementation for Modbus ASCII/RTU.
+ * Copyright (c) 2006 Christian Walter <wolti@sil.at>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * File: $Id: mbfuncother.c,v 1.8 2006/12/07 22:10:34 wolti Exp $
+ */
+
+/* ----------------------- System includes ----------------------------------*/
+#include "stdlib.h"
+#include "string.h"
+
+/* ----------------------- Platform includes --------------------------------*/
+#include "port.h"
+
+/* ----------------------- Modbus includes ----------------------------------*/
+#include "mb.h"
+#include "mbframe.h"
+#include "mbproto.h"
+#include "mbconfig.h"
+
+#if MB_FUNC_OTHER_REP_SLAVEID_ENABLED > 0
+
+/* ----------------------- Static variables ---------------------------------*/
+static UCHAR    ucMBSlaveID[MB_FUNC_OTHER_REP_SLAVEID_BUF];
+static USHORT   usMBSlaveIDLen;
+
+/* ----------------------- Start implementation -----------------------------*/
+
+eMBErrorCode
+eMBSetSlaveID( UCHAR ucSlaveID, BOOL xIsRunning,
+               UCHAR const *pucAdditional, USHORT usAdditionalLen )
+{
+    eMBErrorCode    eStatus = MB_ENOERR;
+
+    /* the first byte and second byte in the buffer is reserved for
+     * the parameter ucSlaveID and the running flag. The rest of
+     * the buffer is available for additional data. */
+    if( usAdditionalLen + 2 < MB_FUNC_OTHER_REP_SLAVEID_BUF )
+    {
+        usMBSlaveIDLen = 0;
+        ucMBSlaveID[usMBSlaveIDLen++] = ucSlaveID;
+        ucMBSlaveID[usMBSlaveIDLen++] = ( UCHAR )( xIsRunning ? 0xFF : 0x00 );
+        if( usAdditionalLen > 0 )
+        {
+            memcpy( &ucMBSlaveID[usMBSlaveIDLen], pucAdditional,
+                    ( size_t )usAdditionalLen );
+            usMBSlaveIDLen += usAdditionalLen;
+        }
+    }
+    else
+    {
+        eStatus = MB_ENORES;
+    }
+    return eStatus;
+}
+
+eMBException
+eMBFuncReportSlaveID( UCHAR * pucFrame, USHORT * usLen )
+{
+    memcpy( &pucFrame[MB_PDU_DATA_OFF], &ucMBSlaveID[0], ( size_t )usMBSlaveIDLen );
+    *usLen = ( USHORT )( MB_PDU_DATA_OFF + usMBSlaveIDLen );
+    return MB_EX_NONE;
+}
+
+#endif
diff --git a/apps/modbus/functions/mbutils.c b/apps/modbus/functions/mbutils.c
new file mode 100644
index 000000000..6a725703e
--- /dev/null
+++ b/apps/modbus/functions/mbutils.c
@@ -0,0 +1,141 @@
+/* 
+ * FreeModbus Libary: A portable Modbus implementation for Modbus ASCII/RTU.
+ * Copyright (c) 2006 Christian Walter <wolti@sil.at>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * File: $Id: mbutils.c,v 1.6 2007/02/18 23:49:07 wolti Exp $
+ */
+
+/* ----------------------- System includes ----------------------------------*/
+#include "stdlib.h"
+#include "string.h"
+
+/* ----------------------- Platform includes --------------------------------*/
+#include "port.h"
+
+/* ----------------------- Modbus includes ----------------------------------*/
+#include "mb.h"
+#include "mbproto.h"
+
+/* ----------------------- Defines ------------------------------------------*/
+#define BITS_UCHAR      8U
+
+/* ----------------------- Start implementation -----------------------------*/
+void
+xMBUtilSetBits( UCHAR * ucByteBuf, USHORT usBitOffset, UCHAR ucNBits,
+                UCHAR ucValue )
+{
+    USHORT          usWordBuf;
+    USHORT          usMask;
+    USHORT          usByteOffset;
+    USHORT          usNPreBits;
+    USHORT          usValue = ucValue;
+
+    assert( ucNBits <= 8 );
+    assert( ( size_t )BITS_UCHAR == sizeof( UCHAR ) * 8 );
+
+    /* Calculate byte offset for first byte containing the bit values starting
+     * at usBitOffset. */
+    usByteOffset = ( USHORT )( ( usBitOffset ) / BITS_UCHAR );
+
+    /* How many bits precede our bits to set. */
+    usNPreBits = ( USHORT )( usBitOffset - usByteOffset * BITS_UCHAR );
+
+    /* Move bit field into position over bits to set */
+    usValue <<= usNPreBits;
+
+    /* Prepare a mask for setting the new bits. */
+    usMask = ( USHORT )( ( 1 << ( USHORT ) ucNBits ) - 1 );
+    usMask <<= usBitOffset - usByteOffset * BITS_UCHAR;
+
+    /* copy bits into temporary storage. */
+    usWordBuf = ucByteBuf[usByteOffset];
+    usWordBuf |= ucByteBuf[usByteOffset + 1] << BITS_UCHAR;
+
+    /* Zero out bit field bits and then or value bits into them. */
+    usWordBuf = ( USHORT )( ( usWordBuf & ( ~usMask ) ) | usValue );
+
+    /* move bits back into storage */
+    ucByteBuf[usByteOffset] = ( UCHAR )( usWordBuf & 0xFF );
+    ucByteBuf[usByteOffset + 1] = ( UCHAR )( usWordBuf >> BITS_UCHAR );
+}
+
+UCHAR
+xMBUtilGetBits( UCHAR * ucByteBuf, USHORT usBitOffset, UCHAR ucNBits )
+{
+    USHORT          usWordBuf;
+    USHORT          usMask;
+    USHORT          usByteOffset;
+    USHORT          usNPreBits;
+
+    /* Calculate byte offset for first byte containing the bit values starting
+     * at usBitOffset. */
+    usByteOffset = ( USHORT )( ( usBitOffset ) / BITS_UCHAR );
+
+    /* How many bits precede our bits to set. */
+    usNPreBits = ( USHORT )( usBitOffset - usByteOffset * BITS_UCHAR );
+
+    /* Prepare a mask for setting the new bits. */
+    usMask = ( USHORT )( ( 1 << ( USHORT ) ucNBits ) - 1 );
+
+    /* copy bits into temporary storage. */
+    usWordBuf = ucByteBuf[usByteOffset];
+    usWordBuf |= ucByteBuf[usByteOffset + 1] << BITS_UCHAR;
+
+    /* throw away unneeded bits. */
+    usWordBuf >>= usNPreBits;
+
+    /* mask away bits above the requested bitfield. */
+    usWordBuf &= usMask;
+
+    return ( UCHAR ) usWordBuf;
+}
+
+eMBException
+prveMBError2Exception( eMBErrorCode eErrorCode )
+{
+    eMBException    eStatus;
+
+    switch ( eErrorCode )
+    {
+        case MB_ENOERR:
+            eStatus = MB_EX_NONE;
+            break;
+
+        case MB_ENOREG:
+            eStatus = MB_EX_ILLEGAL_DATA_ADDRESS;
+            break;
+
+        case MB_ETIMEDOUT:
+            eStatus = MB_EX_SLAVE_BUSY;
+            break;
+
+        default:
+            eStatus = MB_EX_SLAVE_DEVICE_FAILURE;
+            break;
+    }
+
+    return eStatus;
+}
diff --git a/apps/modbus/mb.c b/apps/modbus/mb.c
new file mode 100644
index 000000000..e7f372de8
--- /dev/null
+++ b/apps/modbus/mb.c
@@ -0,0 +1,412 @@
+/* 
+ * FreeModbus Libary: A portable Modbus implementation for Modbus ASCII/RTU.
+ * Copyright (c) 2006 Christian Walter <wolti@sil.at>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * File: $Id: mb.c,v 1.28 2010/06/06 13:54:40 wolti Exp $
+ */
+
+/* ----------------------- System includes ----------------------------------*/
+#include "stdlib.h"
+#include "string.h"
+
+/* ----------------------- Platform includes --------------------------------*/
+#include "port.h"
+
+/* ----------------------- Modbus includes ----------------------------------*/
+#include "mb.h"
+#include "mbconfig.h"
+#include "mbframe.h"
+#include "mbproto.h"
+#include "mbfunc.h"
+
+#include "mbport.h"
+#if MB_RTU_ENABLED == 1
+#include "mbrtu.h"
+#endif
+#if MB_ASCII_ENABLED == 1
+#include "mbascii.h"
+#endif
+#if MB_TCP_ENABLED == 1
+#include "mbtcp.h"
+#endif
+
+#ifndef MB_PORT_HAS_CLOSE
+#define MB_PORT_HAS_CLOSE 0
+#endif
+
+/* ----------------------- Static variables ---------------------------------*/
+
+static UCHAR    ucMBAddress;
+static eMBMode  eMBCurrentMode;
+
+static enum
+{
+    STATE_ENABLED,
+    STATE_DISABLED,
+    STATE_NOT_INITIALIZED
+} eMBState = STATE_NOT_INITIALIZED;
+
+/* Functions pointer which are initialized in eMBInit( ). Depending on the
+ * mode (RTU or ASCII) the are set to the correct implementations.
+ */
+static peMBFrameSend peMBFrameSendCur;
+static pvMBFrameStart pvMBFrameStartCur;
+static pvMBFrameStop pvMBFrameStopCur;
+static peMBFrameReceive peMBFrameReceiveCur;
+static pvMBFrameClose pvMBFrameCloseCur;
+
+/* Callback functions required by the porting layer. They are called when
+ * an external event has happend which includes a timeout or the reception
+ * or transmission of a character.
+ */
+BOOL( *pxMBFrameCBByteReceived ) ( void );
+BOOL( *pxMBFrameCBTransmitterEmpty ) ( void );
+BOOL( *pxMBPortCBTimerExpired ) ( void );
+
+BOOL( *pxMBFrameCBReceiveFSMCur ) ( void );
+BOOL( *pxMBFrameCBTransmitFSMCur ) ( void );
+
+/* An array of Modbus functions handlers which associates Modbus function
+ * codes with implementing functions.
+ */
+static xMBFunctionHandler xFuncHandlers[MB_FUNC_HANDLERS_MAX] = {
+#if MB_FUNC_OTHER_REP_SLAVEID_ENABLED > 0
+    {MB_FUNC_OTHER_REPORT_SLAVEID, eMBFuncReportSlaveID},
+#endif
+#if MB_FUNC_READ_INPUT_ENABLED > 0
+    {MB_FUNC_READ_INPUT_REGISTER, eMBFuncReadInputRegister},
+#endif
+#if MB_FUNC_READ_HOLDING_ENABLED > 0
+    {MB_FUNC_READ_HOLDING_REGISTER, eMBFuncReadHoldingRegister},
+#endif
+#if MB_FUNC_WRITE_MULTIPLE_HOLDING_ENABLED > 0
+    {MB_FUNC_WRITE_MULTIPLE_REGISTERS, eMBFuncWriteMultipleHoldingRegister},
+#endif
+#if MB_FUNC_WRITE_HOLDING_ENABLED > 0
+    {MB_FUNC_WRITE_REGISTER, eMBFuncWriteHoldingRegister},
+#endif
+#if MB_FUNC_READWRITE_HOLDING_ENABLED > 0
+    {MB_FUNC_READWRITE_MULTIPLE_REGISTERS, eMBFuncReadWriteMultipleHoldingRegister},
+#endif
+#if MB_FUNC_READ_COILS_ENABLED > 0
+    {MB_FUNC_READ_COILS, eMBFuncReadCoils},
+#endif
+#if MB_FUNC_WRITE_COIL_ENABLED > 0
+    {MB_FUNC_WRITE_SINGLE_COIL, eMBFuncWriteCoil},
+#endif
+#if MB_FUNC_WRITE_MULTIPLE_COILS_ENABLED > 0
+    {MB_FUNC_WRITE_MULTIPLE_COILS, eMBFuncWriteMultipleCoils},
+#endif
+#if MB_FUNC_READ_DISCRETE_INPUTS_ENABLED > 0
+    {MB_FUNC_READ_DISCRETE_INPUTS, eMBFuncReadDiscreteInputs},
+#endif
+};
+
+/* ----------------------- Start implementation -----------------------------*/
+eMBErrorCode
+eMBInit( eMBMode eMode, UCHAR ucSlaveAddress, UCHAR ucPort, ULONG ulBaudRate, eMBParity eParity )
+{
+    eMBErrorCode    eStatus = MB_ENOERR;
+
+    /* check preconditions */
+    if( ( ucSlaveAddress == MB_ADDRESS_BROADCAST ) ||
+        ( ucSlaveAddress < MB_ADDRESS_MIN ) || ( ucSlaveAddress > MB_ADDRESS_MAX ) )
+    {
+        eStatus = MB_EINVAL;
+    }
+    else
+    {
+        ucMBAddress = ucSlaveAddress;
+
+        switch ( eMode )
+        {
+#if MB_RTU_ENABLED > 0
+        case MB_RTU:
+            pvMBFrameStartCur = eMBRTUStart;
+            pvMBFrameStopCur = eMBRTUStop;
+            peMBFrameSendCur = eMBRTUSend;
+            peMBFrameReceiveCur = eMBRTUReceive;
+            pvMBFrameCloseCur = MB_PORT_HAS_CLOSE ? vMBPortClose : NULL;
+            pxMBFrameCBByteReceived = xMBRTUReceiveFSM;
+            pxMBFrameCBTransmitterEmpty = xMBRTUTransmitFSM;
+            pxMBPortCBTimerExpired = xMBRTUTimerT35Expired;
+
+            eStatus = eMBRTUInit( ucMBAddress, ucPort, ulBaudRate, eParity );
+            break;
+#endif
+#if MB_ASCII_ENABLED > 0
+        case MB_ASCII:
+            pvMBFrameStartCur = eMBASCIIStart;
+            pvMBFrameStopCur = eMBASCIIStop;
+            peMBFrameSendCur = eMBASCIISend;
+            peMBFrameReceiveCur = eMBASCIIReceive;
+            pvMBFrameCloseCur = MB_PORT_HAS_CLOSE ? vMBPortClose : NULL;
+            pxMBFrameCBByteReceived = xMBASCIIReceiveFSM;
+            pxMBFrameCBTransmitterEmpty = xMBASCIITransmitFSM;
+            pxMBPortCBTimerExpired = xMBASCIITimerT1SExpired;
+
+            eStatus = eMBASCIIInit( ucMBAddress, ucPort, ulBaudRate, eParity );
+            break;
+#endif
+        default:
+            eStatus = MB_EINVAL;
+        }
+
+        if( eStatus == MB_ENOERR )
+        {
+            if( !xMBPortEventInit(  ) )
+            {
+                /* port dependent event module initalization failed. */
+                eStatus = MB_EPORTERR;
+            }
+            else
+            {
+                eMBCurrentMode = eMode;
+                eMBState = STATE_DISABLED;
+            }
+        }
+    }
+    return eStatus;
+}
+
+#if MB_TCP_ENABLED > 0
+eMBErrorCode
+eMBTCPInit( USHORT ucTCPPort )
+{
+    eMBErrorCode    eStatus = MB_ENOERR;
+
+    if( ( eStatus = eMBTCPDoInit( ucTCPPort ) ) != MB_ENOERR )
+    {
+        eMBState = STATE_DISABLED;
+    }
+    else if( !xMBPortEventInit(  ) )
+    {
+        /* Port dependent event module initalization failed. */
+        eStatus = MB_EPORTERR;
+    }
+    else
+    {
+        pvMBFrameStartCur = eMBTCPStart;
+        pvMBFrameStopCur = eMBTCPStop;
+        peMBFrameReceiveCur = eMBTCPReceive;
+        peMBFrameSendCur = eMBTCPSend;
+        pvMBFrameCloseCur = MB_PORT_HAS_CLOSE ? vMBTCPPortClose : NULL;
+        ucMBAddress = MB_TCP_PSEUDO_ADDRESS;
+        eMBCurrentMode = MB_TCP;
+        eMBState = STATE_DISABLED;
+    }
+    return eStatus;
+}
+#endif
+
+eMBErrorCode
+eMBRegisterCB( UCHAR ucFunctionCode, pxMBFunctionHandler pxHandler )
+{
+    int             i;
+    eMBErrorCode    eStatus;
+
+    if( ( 0 < ucFunctionCode ) && ( ucFunctionCode <= 127 ) )
+    {
+        ENTER_CRITICAL_SECTION(  );
+        if( pxHandler != NULL )
+        {
+            for( i = 0; i < MB_FUNC_HANDLERS_MAX; i++ )
+            {
+                if( ( xFuncHandlers[i].pxHandler == NULL ) ||
+                    ( xFuncHandlers[i].pxHandler == pxHandler ) )
+                {
+                    xFuncHandlers[i].ucFunctionCode = ucFunctionCode;
+                    xFuncHandlers[i].pxHandler = pxHandler;
+                    break;
+                }
+            }
+            eStatus = ( i != MB_FUNC_HANDLERS_MAX ) ? MB_ENOERR : MB_ENORES;
+        }
+        else
+        {
+            for( i = 0; i < MB_FUNC_HANDLERS_MAX; i++ )
+            {
+                if( xFuncHandlers[i].ucFunctionCode == ucFunctionCode )
+                {
+                    xFuncHandlers[i].ucFunctionCode = 0;
+                    xFuncHandlers[i].pxHandler = NULL;
+                    break;
+                }
+            }
+            /* Remove can't fail. */
+            eStatus = MB_ENOERR;
+        }
+        EXIT_CRITICAL_SECTION(  );
+    }
+    else
+    {
+        eStatus = MB_EINVAL;
+    }
+    return eStatus;
+}
+
+
+eMBErrorCode
+eMBClose( void )
+{
+    eMBErrorCode    eStatus = MB_ENOERR;
+
+    if( eMBState == STATE_DISABLED )
+    {
+        if( pvMBFrameCloseCur != NULL )
+        {
+            pvMBFrameCloseCur(  );
+        }
+    }
+    else
+    {
+        eStatus = MB_EILLSTATE;
+    }
+    return eStatus;
+}
+
+eMBErrorCode
+eMBEnable( void )
+{
+    eMBErrorCode    eStatus = MB_ENOERR;
+
+    if( eMBState == STATE_DISABLED )
+    {
+        /* Activate the protocol stack. */
+        pvMBFrameStartCur(  );
+        eMBState = STATE_ENABLED;
+    }
+    else
+    {
+        eStatus = MB_EILLSTATE;
+    }
+    return eStatus;
+}
+
+eMBErrorCode
+eMBDisable( void )
+{
+    eMBErrorCode    eStatus;
+
+    if( eMBState == STATE_ENABLED )
+    {
+        pvMBFrameStopCur(  );
+        eMBState = STATE_DISABLED;
+        eStatus = MB_ENOERR;
+    }
+    else if( eMBState == STATE_DISABLED )
+    {
+        eStatus = MB_ENOERR;
+    }
+    else
+    {
+        eStatus = MB_EILLSTATE;
+    }
+    return eStatus;
+}
+
+eMBErrorCode
+eMBPoll( void )
+{
+    static UCHAR   *ucMBFrame;
+    static UCHAR    ucRcvAddress;
+    static UCHAR    ucFunctionCode;
+    static USHORT   usLength;
+    static eMBException eException;
+
+    int             i;
+    eMBErrorCode    eStatus = MB_ENOERR;
+    eMBEventType    eEvent;
+
+    /* Check if the protocol stack is ready. */
+    if( eMBState != STATE_ENABLED )
+    {
+        return MB_EILLSTATE;
+    }
+
+    /* Check if there is a event available. If not return control to caller.
+     * Otherwise we will handle the event. */
+    if( xMBPortEventGet( &eEvent ) == TRUE )
+    {
+        switch ( eEvent )
+        {
+        case EV_READY:
+            break;
+
+        case EV_FRAME_RECEIVED:
+            eStatus = peMBFrameReceiveCur( &ucRcvAddress, &ucMBFrame, &usLength );
+            if( eStatus == MB_ENOERR )
+            {
+                /* Check if the frame is for us. If not ignore the frame. */
+                if( ( ucRcvAddress == ucMBAddress ) || ( ucRcvAddress == MB_ADDRESS_BROADCAST ) )
+                {
+                    ( void )xMBPortEventPost( EV_EXECUTE );
+                }
+            }
+            break;
+
+        case EV_EXECUTE:
+            ucFunctionCode = ucMBFrame[MB_PDU_FUNC_OFF];
+            eException = MB_EX_ILLEGAL_FUNCTION;
+            for( i = 0; i < MB_FUNC_HANDLERS_MAX; i++ )
+            {
+                /* No more function handlers registered. Abort. */
+                if( xFuncHandlers[i].ucFunctionCode == 0 )
+                {
+                    break;
+                }
+                else if( xFuncHandlers[i].ucFunctionCode == ucFunctionCode )
+                {
+                    eException = xFuncHandlers[i].pxHandler( ucMBFrame, &usLength );
+                    break;
+                }
+            }
+
+            /* If the request was not sent to the broadcast address we
+             * return a reply. */
+            if( ucRcvAddress != MB_ADDRESS_BROADCAST )
+            {
+                if( eException != MB_EX_NONE )
+                {
+                    /* An exception occured. Build an error frame. */
+                    usLength = 0;
+                    ucMBFrame[usLength++] = ( UCHAR )( ucFunctionCode | MB_FUNC_ERROR );
+                    ucMBFrame[usLength++] = eException;
+                }
+                if( ( eMBCurrentMode == MB_ASCII ) && MB_ASCII_TIMEOUT_WAIT_BEFORE_SEND_MS )
+                {
+                    vMBPortTimersDelay( MB_ASCII_TIMEOUT_WAIT_BEFORE_SEND_MS );
+                }                
+                eStatus = peMBFrameSendCur( ucMBAddress, ucMBFrame, usLength );
+            }
+            break;
+
+        case EV_FRAME_SENT:
+            break;
+        }
+    }
+    return MB_ENOERR;
+}
diff --git a/apps/modbus/rtu/mbcrc.c b/apps/modbus/rtu/mbcrc.c
new file mode 100644
index 000000000..29b9ea765
--- /dev/null
+++ b/apps/modbus/rtu/mbcrc.c
@@ -0,0 +1,98 @@
+/* 
+ * FreeModbus Libary: A portable Modbus implementation for Modbus ASCII/RTU.
+ * Copyright (c) 2006 Christian Walter <wolti@sil.at>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * File: $Id: mbcrc.c,v 1.7 2007/02/18 23:50:27 wolti Exp $
+ */
+
+/* ----------------------- Platform includes --------------------------------*/
+#include "port.h"
+
+static const UCHAR aucCRCHi[] = {
+    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
+    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
+    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
+    0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
+    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
+    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
+    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
+    0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
+    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
+    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
+    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
+    0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 
+    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
+    0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 
+    0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
+    0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
+    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 
+    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
+    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
+    0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
+    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
+    0x00, 0xC1, 0x81, 0x40
+};
+
+static const UCHAR aucCRCLo[] = {
+    0x00, 0xC0, 0xC1, 0x01, 0xC3, 0x03, 0x02, 0xC2, 0xC6, 0x06, 0x07, 0xC7,
+    0x05, 0xC5, 0xC4, 0x04, 0xCC, 0x0C, 0x0D, 0xCD, 0x0F, 0xCF, 0xCE, 0x0E,
+    0x0A, 0xCA, 0xCB, 0x0B, 0xC9, 0x09, 0x08, 0xC8, 0xD8, 0x18, 0x19, 0xD9,
+    0x1B, 0xDB, 0xDA, 0x1A, 0x1E, 0xDE, 0xDF, 0x1F, 0xDD, 0x1D, 0x1C, 0xDC,
+    0x14, 0xD4, 0xD5, 0x15, 0xD7, 0x17, 0x16, 0xD6, 0xD2, 0x12, 0x13, 0xD3,
+    0x11, 0xD1, 0xD0, 0x10, 0xF0, 0x30, 0x31, 0xF1, 0x33, 0xF3, 0xF2, 0x32,
+    0x36, 0xF6, 0xF7, 0x37, 0xF5, 0x35, 0x34, 0xF4, 0x3C, 0xFC, 0xFD, 0x3D,
+    0xFF, 0x3F, 0x3E, 0xFE, 0xFA, 0x3A, 0x3B, 0xFB, 0x39, 0xF9, 0xF8, 0x38, 
+    0x28, 0xE8, 0xE9, 0x29, 0xEB, 0x2B, 0x2A, 0xEA, 0xEE, 0x2E, 0x2F, 0xEF,
+    0x2D, 0xED, 0xEC, 0x2C, 0xE4, 0x24, 0x25, 0xE5, 0x27, 0xE7, 0xE6, 0x26,
+    0x22, 0xE2, 0xE3, 0x23, 0xE1, 0x21, 0x20, 0xE0, 0xA0, 0x60, 0x61, 0xA1,
+    0x63, 0xA3, 0xA2, 0x62, 0x66, 0xA6, 0xA7, 0x67, 0xA5, 0x65, 0x64, 0xA4,
+    0x6C, 0xAC, 0xAD, 0x6D, 0xAF, 0x6F, 0x6E, 0xAE, 0xAA, 0x6A, 0x6B, 0xAB, 
+    0x69, 0xA9, 0xA8, 0x68, 0x78, 0xB8, 0xB9, 0x79, 0xBB, 0x7B, 0x7A, 0xBA,
+    0xBE, 0x7E, 0x7F, 0xBF, 0x7D, 0xBD, 0xBC, 0x7C, 0xB4, 0x74, 0x75, 0xB5,
+    0x77, 0xB7, 0xB6, 0x76, 0x72, 0xB2, 0xB3, 0x73, 0xB1, 0x71, 0x70, 0xB0,
+    0x50, 0x90, 0x91, 0x51, 0x93, 0x53, 0x52, 0x92, 0x96, 0x56, 0x57, 0x97,
+    0x55, 0x95, 0x94, 0x54, 0x9C, 0x5C, 0x5D, 0x9D, 0x5F, 0x9F, 0x9E, 0x5E,
+    0x5A, 0x9A, 0x9B, 0x5B, 0x99, 0x59, 0x58, 0x98, 0x88, 0x48, 0x49, 0x89,
+    0x4B, 0x8B, 0x8A, 0x4A, 0x4E, 0x8E, 0x8F, 0x4F, 0x8D, 0x4D, 0x4C, 0x8C,
+    0x44, 0x84, 0x85, 0x45, 0x87, 0x47, 0x46, 0x86, 0x82, 0x42, 0x43, 0x83,
+    0x41, 0x81, 0x80, 0x40
+};
+
+USHORT
+usMBCRC16( UCHAR * pucFrame, USHORT usLen )
+{
+    UCHAR           ucCRCHi = 0xFF;
+    UCHAR           ucCRCLo = 0xFF;
+    int             iIndex;
+
+    while( usLen-- )
+    {
+        iIndex = ucCRCLo ^ *( pucFrame++ );
+        ucCRCLo = ( UCHAR )( ucCRCHi ^ aucCRCHi[iIndex] );
+        ucCRCHi = aucCRCLo[iIndex];
+    }
+    return ( USHORT )( ucCRCHi << 8 | ucCRCLo );
+}
diff --git a/apps/modbus/rtu/mbcrc.h b/apps/modbus/rtu/mbcrc.h
new file mode 100644
index 000000000..db227763f
--- /dev/null
+++ b/apps/modbus/rtu/mbcrc.h
@@ -0,0 +1,36 @@
+/* 
+ * FreeModbus Libary: A portable Modbus implementation for Modbus ASCII/RTU.
+ * Copyright (c) 2006 Christian Walter <wolti@sil.at>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * File: $Id: mbcrc.h,v 1.5 2006/12/07 22:10:34 wolti Exp $
+ */
+
+#ifndef _MB_CRC_H
+#define _MB_CRC_H
+
+USHORT          usMBCRC16( UCHAR * pucFrame, USHORT usLen );
+
+#endif
diff --git a/apps/modbus/rtu/mbrtu.c b/apps/modbus/rtu/mbrtu.c
new file mode 100644
index 000000000..fc9b854ff
--- /dev/null
+++ b/apps/modbus/rtu/mbrtu.c
@@ -0,0 +1,355 @@
+/* 
+ * FreeModbus Libary: A portable Modbus implementation for Modbus ASCII/RTU.
+ * Copyright (c) 2006 Christian Walter <wolti@sil.at>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * File: $Id: mbrtu.c,v 1.18 2007/09/12 10:15:56 wolti Exp $
+ */
+
+/* ----------------------- System includes ----------------------------------*/
+#include "stdlib.h"
+#include "string.h"
+
+/* ----------------------- Platform includes --------------------------------*/
+#include "port.h"
+
+/* ----------------------- Modbus includes ----------------------------------*/
+#include "mb.h"
+#include "mbrtu.h"
+#include "mbframe.h"
+
+#include "mbcrc.h"
+#include "mbport.h"
+
+/* ----------------------- Defines ------------------------------------------*/
+#define MB_SER_PDU_SIZE_MIN     4       /*!< Minimum size of a Modbus RTU frame. */
+#define MB_SER_PDU_SIZE_MAX     256     /*!< Maximum size of a Modbus RTU frame. */
+#define MB_SER_PDU_SIZE_CRC     2       /*!< Size of CRC field in PDU. */
+#define MB_SER_PDU_ADDR_OFF     0       /*!< Offset of slave address in Ser-PDU. */
+#define MB_SER_PDU_PDU_OFF      1       /*!< Offset of Modbus-PDU in Ser-PDU. */
+
+/* ----------------------- Type definitions ---------------------------------*/
+typedef enum
+{
+    STATE_RX_INIT,              /*!< Receiver is in initial state. */
+    STATE_RX_IDLE,              /*!< Receiver is in idle state. */
+    STATE_RX_RCV,               /*!< Frame is beeing received. */
+    STATE_RX_ERROR              /*!< If the frame is invalid. */
+} eMBRcvState;
+
+typedef enum
+{
+    STATE_TX_IDLE,              /*!< Transmitter is in idle state. */
+    STATE_TX_XMIT               /*!< Transmitter is in transfer state. */
+} eMBSndState;
+
+/* ----------------------- Static variables ---------------------------------*/
+static volatile eMBSndState eSndState;
+static volatile eMBRcvState eRcvState;
+
+volatile UCHAR  ucRTUBuf[MB_SER_PDU_SIZE_MAX];
+
+static volatile UCHAR *pucSndBufferCur;
+static volatile USHORT usSndBufferCount;
+
+static volatile USHORT usRcvBufferPos;
+
+/* ----------------------- Start implementation -----------------------------*/
+eMBErrorCode
+eMBRTUInit( UCHAR ucSlaveAddress, UCHAR ucPort, ULONG ulBaudRate, eMBParity eParity )
+{
+    eMBErrorCode    eStatus = MB_ENOERR;
+    ULONG           usTimerT35_50us;
+
+    ( void )ucSlaveAddress;
+    ENTER_CRITICAL_SECTION(  );
+
+    /* Modbus RTU uses 8 Databits. */
+    if( xMBPortSerialInit( ucPort, ulBaudRate, 8, eParity ) != TRUE )
+    {
+        eStatus = MB_EPORTERR;
+    }
+    else
+    {
+        /* If baudrate > 19200 then we should use the fixed timer values
+         * t35 = 1750us. Otherwise t35 must be 3.5 times the character time.
+         */
+        if( ulBaudRate > 19200 )
+        {
+            usTimerT35_50us = 35;       /* 1800us. */
+        }
+        else
+        {
+            /* The timer reload value for a character is given by:
+             *
+             * ChTimeValue = Ticks_per_1s / ( Baudrate / 11 )
+             *             = 11 * Ticks_per_1s / Baudrate
+             *             = 220000 / Baudrate
+             * The reload for t3.5 is 1.5 times this value and similary
+             * for t3.5.
+             */
+            usTimerT35_50us = ( 7UL * 220000UL ) / ( 2UL * ulBaudRate );
+        }
+        if( xMBPortTimersInit( ( USHORT ) usTimerT35_50us ) != TRUE )
+        {
+            eStatus = MB_EPORTERR;
+        }
+    }
+    EXIT_CRITICAL_SECTION(  );
+
+    return eStatus;
+}
+
+void
+eMBRTUStart( void )
+{
+    ENTER_CRITICAL_SECTION(  );
+    /* Initially the receiver is in the state STATE_RX_INIT. we start
+     * the timer and if no character is received within t3.5 we change
+     * to STATE_RX_IDLE. This makes sure that we delay startup of the
+     * modbus protocol stack until the bus is free.
+     */
+    eRcvState = STATE_RX_INIT;
+    vMBPortSerialEnable( TRUE, FALSE );
+    vMBPortTimersEnable(  );
+
+    EXIT_CRITICAL_SECTION(  );
+}
+
+void
+eMBRTUStop( void )
+{
+    ENTER_CRITICAL_SECTION(  );
+    vMBPortSerialEnable( FALSE, FALSE );
+    vMBPortTimersDisable(  );
+    EXIT_CRITICAL_SECTION(  );
+}
+
+eMBErrorCode
+eMBRTUReceive( UCHAR * pucRcvAddress, UCHAR ** pucFrame, USHORT * pusLength )
+{
+    BOOL            xFrameReceived = FALSE;
+    eMBErrorCode    eStatus = MB_ENOERR;
+
+    ENTER_CRITICAL_SECTION(  );
+    assert( usRcvBufferPos < MB_SER_PDU_SIZE_MAX );
+
+    /* Length and CRC check */
+    if( ( usRcvBufferPos >= MB_SER_PDU_SIZE_MIN )
+        && ( usMBCRC16( ( UCHAR * ) ucRTUBuf, usRcvBufferPos ) == 0 ) )
+    {
+        /* Save the address field. All frames are passed to the upper layed
+         * and the decision if a frame is used is done there.
+         */
+        *pucRcvAddress = ucRTUBuf[MB_SER_PDU_ADDR_OFF];
+
+        /* Total length of Modbus-PDU is Modbus-Serial-Line-PDU minus
+         * size of address field and CRC checksum.
+         */
+        *pusLength = ( USHORT )( usRcvBufferPos - MB_SER_PDU_PDU_OFF - MB_SER_PDU_SIZE_CRC );
+
+        /* Return the start of the Modbus PDU to the caller. */
+        *pucFrame = ( UCHAR * ) & ucRTUBuf[MB_SER_PDU_PDU_OFF];
+        xFrameReceived = TRUE;
+    }
+    else
+    {
+        eStatus = MB_EIO;
+    }
+
+    EXIT_CRITICAL_SECTION(  );
+    return eStatus;
+}
+
+eMBErrorCode
+eMBRTUSend( UCHAR ucSlaveAddress, const UCHAR * pucFrame, USHORT usLength )
+{
+    eMBErrorCode    eStatus = MB_ENOERR;
+    USHORT          usCRC16;
+
+    ENTER_CRITICAL_SECTION(  );
+
+    /* Check if the receiver is still in idle state. If not we where to
+     * slow with processing the received frame and the master sent another
+     * frame on the network. We have to abort sending the frame.
+     */
+    if( eRcvState == STATE_RX_IDLE )
+    {
+        /* First byte before the Modbus-PDU is the slave address. */
+        pucSndBufferCur = ( UCHAR * ) pucFrame - 1;
+        usSndBufferCount = 1;
+
+        /* Now copy the Modbus-PDU into the Modbus-Serial-Line-PDU. */
+        pucSndBufferCur[MB_SER_PDU_ADDR_OFF] = ucSlaveAddress;
+        usSndBufferCount += usLength;
+
+        /* Calculate CRC16 checksum for Modbus-Serial-Line-PDU. */
+        usCRC16 = usMBCRC16( ( UCHAR * ) pucSndBufferCur, usSndBufferCount );
+        ucRTUBuf[usSndBufferCount++] = ( UCHAR )( usCRC16 & 0xFF );
+        ucRTUBuf[usSndBufferCount++] = ( UCHAR )( usCRC16 >> 8 );
+
+        /* Activate the transmitter. */
+        eSndState = STATE_TX_XMIT;
+        vMBPortSerialEnable( FALSE, TRUE );
+    }
+    else
+    {
+        eStatus = MB_EIO;
+    }
+    EXIT_CRITICAL_SECTION(  );
+    return eStatus;
+}
+
+BOOL
+xMBRTUReceiveFSM( void )
+{
+    BOOL            xTaskNeedSwitch = FALSE;
+    UCHAR           ucByte;
+
+    assert( eSndState == STATE_TX_IDLE );
+
+    /* Always read the character. */
+    ( void )xMBPortSerialGetByte( ( CHAR * ) & ucByte );
+
+    switch ( eRcvState )
+    {
+        /* If we have received a character in the init state we have to
+         * wait until the frame is finished.
+         */
+    case STATE_RX_INIT:
+        vMBPortTimersEnable(  );
+        break;
+
+        /* In the error state we wait until all characters in the
+         * damaged frame are transmitted.
+         */
+    case STATE_RX_ERROR:
+        vMBPortTimersEnable(  );
+        break;
+
+        /* In the idle state we wait for a new character. If a character
+         * is received the t1.5 and t3.5 timers are started and the
+         * receiver is in the state STATE_RX_RECEIVCE.
+         */
+    case STATE_RX_IDLE:
+        usRcvBufferPos = 0;
+        ucRTUBuf[usRcvBufferPos++] = ucByte;
+        eRcvState = STATE_RX_RCV;
+
+        /* Enable t3.5 timers. */
+        vMBPortTimersEnable(  );
+        break;
+
+        /* We are currently receiving a frame. Reset the timer after
+         * every character received. If more than the maximum possible
+         * number of bytes in a modbus frame is received the frame is
+         * ignored.
+         */
+    case STATE_RX_RCV:
+        if( usRcvBufferPos < MB_SER_PDU_SIZE_MAX )
+        {
+            ucRTUBuf[usRcvBufferPos++] = ucByte;
+        }
+        else
+        {
+            eRcvState = STATE_RX_ERROR;
+        }
+        vMBPortTimersEnable(  );
+        break;
+    }
+    return xTaskNeedSwitch;
+}
+
+BOOL
+xMBRTUTransmitFSM( void )
+{
+    BOOL            xNeedPoll = FALSE;
+
+    assert( eRcvState == STATE_RX_IDLE );
+
+    switch ( eSndState )
+    {
+        /* We should not get a transmitter event if the transmitter is in
+         * idle state.  */
+    case STATE_TX_IDLE:
+        /* enable receiver/disable transmitter. */
+        vMBPortSerialEnable( TRUE, FALSE );
+        break;
+
+    case STATE_TX_XMIT:
+        /* check if we are finished. */
+        if( usSndBufferCount != 0 )
+        {
+            xMBPortSerialPutByte( ( CHAR )*pucSndBufferCur );
+            pucSndBufferCur++;  /* next byte in sendbuffer. */
+            usSndBufferCount--;
+        }
+        else
+        {
+            xNeedPoll = xMBPortEventPost( EV_FRAME_SENT );
+            /* Disable transmitter. This prevents another transmit buffer
+             * empty interrupt. */
+            vMBPortSerialEnable( TRUE, FALSE );
+            eSndState = STATE_TX_IDLE;
+        }
+        break;
+    }
+
+    return xNeedPoll;
+}
+
+BOOL
+xMBRTUTimerT35Expired( void )
+{
+    BOOL            xNeedPoll = FALSE;
+
+    switch ( eRcvState )
+    {
+        /* Timer t35 expired. Startup phase is finished. */
+    case STATE_RX_INIT:
+        xNeedPoll = xMBPortEventPost( EV_READY );
+        break;
+
+        /* A frame was received and t35 expired. Notify the listener that
+         * a new frame was received. */
+    case STATE_RX_RCV:
+        xNeedPoll = xMBPortEventPost( EV_FRAME_RECEIVED );
+        break;
+
+        /* An error occured while receiving the frame. */
+    case STATE_RX_ERROR:
+        break;
+
+        /* Function called in an illegal state. */
+    default:
+        assert( ( eRcvState == STATE_RX_INIT ) ||
+                ( eRcvState == STATE_RX_RCV ) || ( eRcvState == STATE_RX_ERROR ) );
+    }
+
+    vMBPortTimersDisable(  );
+    eRcvState = STATE_RX_IDLE;
+
+    return xNeedPoll;
+}
diff --git a/apps/modbus/rtu/mbrtu.h b/apps/modbus/rtu/mbrtu.h
new file mode 100644
index 000000000..8d8bd1f0a
--- /dev/null
+++ b/apps/modbus/rtu/mbrtu.h
@@ -0,0 +1,51 @@
+/* 
+ * FreeModbus Libary: A portable Modbus implementation for Modbus ASCII/RTU.
+ * Copyright (c) 2006 Christian Walter <wolti@sil.at>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * File: $Id: mbrtu.h,v 1.9 2006/12/07 22:10:34 wolti Exp $
+ */
+
+#ifndef _MB_RTU_H
+#define _MB_RTU_H
+
+#ifdef __cplusplus
+PR_BEGIN_EXTERN_C
+#endif
+    eMBErrorCode eMBRTUInit( UCHAR slaveAddress, UCHAR ucPort, ULONG ulBaudRate,
+                             eMBParity eParity );
+void            eMBRTUStart( void );
+void            eMBRTUStop( void );
+eMBErrorCode    eMBRTUReceive( UCHAR * pucRcvAddress, UCHAR ** pucFrame, USHORT * pusLength );
+eMBErrorCode    eMBRTUSend( UCHAR slaveAddress, const UCHAR * pucFrame, USHORT usLength );
+BOOL            xMBRTUReceiveFSM( void );
+BOOL            xMBRTUTransmitFSM( void );
+BOOL            xMBRTUTimerT15Expired( void );
+BOOL            xMBRTUTimerT35Expired( void );
+
+#ifdef __cplusplus
+PR_END_EXTERN_C
+#endif
+#endif
diff --git a/apps/modbus/tcp/mbtcp.c b/apps/modbus/tcp/mbtcp.c
new file mode 100644
index 000000000..fb06144ae
--- /dev/null
+++ b/apps/modbus/tcp/mbtcp.c
@@ -0,0 +1,158 @@
+/* 
+ * FreeModbus Libary: A portable Modbus implementation for Modbus ASCII/RTU.
+ * Copyright (c) 2006 Christian Walter <wolti@sil.at>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * File: $Id: mbtcp.c,v 1.3 2006/12/07 22:10:34 wolti Exp $
+ */
+
+/* ----------------------- System includes ----------------------------------*/
+#include "stdlib.h"
+#include "string.h"
+
+/* ----------------------- Platform includes --------------------------------*/
+#include "port.h"
+
+/* ----------------------- Modbus includes ----------------------------------*/
+#include "mb.h"
+#include "mbconfig.h"
+#include "mbtcp.h"
+#include "mbframe.h"
+#include "mbport.h"
+
+#if MB_TCP_ENABLED > 0
+
+/* ----------------------- Defines ------------------------------------------*/
+
+/* ----------------------- MBAP Header --------------------------------------*/
+/*
+ *
+ * <------------------------ MODBUS TCP/IP ADU(1) ------------------------->
+ *              <----------- MODBUS PDU (1') ---------------->
+ *  +-----------+---------------+------------------------------------------+
+ *  | TID | PID | Length | UID  |Code | Data                               |
+ *  +-----------+---------------+------------------------------------------+
+ *  |     |     |        |      |                                           
+ * (2)   (3)   (4)      (5)    (6)                                          
+ *
+ * (2)  ... MB_TCP_TID          = 0 (Transaction Identifier - 2 Byte) 
+ * (3)  ... MB_TCP_PID          = 2 (Protocol Identifier - 2 Byte)
+ * (4)  ... MB_TCP_LEN          = 4 (Number of bytes - 2 Byte)
+ * (5)  ... MB_TCP_UID          = 6 (Unit Identifier - 1 Byte)
+ * (6)  ... MB_TCP_FUNC         = 7 (Modbus Function Code)
+ *
+ * (1)  ... Modbus TCP/IP Application Data Unit
+ * (1') ... Modbus Protocol Data Unit
+ */
+
+#define MB_TCP_TID          0
+#define MB_TCP_PID          2
+#define MB_TCP_LEN          4
+#define MB_TCP_UID          6
+#define MB_TCP_FUNC         7
+
+#define MB_TCP_PROTOCOL_ID  0   /* 0 = Modbus Protocol */
+
+
+/* ----------------------- Start implementation -----------------------------*/
+eMBErrorCode
+eMBTCPDoInit( USHORT ucTCPPort )
+{
+    eMBErrorCode    eStatus = MB_ENOERR;
+
+    if( xMBTCPPortInit( ucTCPPort ) == FALSE )
+    {
+        eStatus = MB_EPORTERR;
+    }
+    return eStatus;
+}
+
+void
+eMBTCPStart( void )
+{
+}
+
+void
+eMBTCPStop( void )
+{
+    /* Make sure that no more clients are connected. */
+    vMBTCPPortDisable( );
+}
+
+eMBErrorCode
+eMBTCPReceive( UCHAR * pucRcvAddress, UCHAR ** ppucFrame, USHORT * pusLength )
+{
+    eMBErrorCode    eStatus = MB_EIO;
+    UCHAR          *pucMBTCPFrame;
+    USHORT          usLength;
+    USHORT          usPID;
+
+    if( xMBTCPPortGetRequest( &pucMBTCPFrame, &usLength ) != FALSE )
+    {
+        usPID = pucMBTCPFrame[MB_TCP_PID] << 8U;
+        usPID |= pucMBTCPFrame[MB_TCP_PID + 1];
+
+        if( usPID == MB_TCP_PROTOCOL_ID )
+        {
+            *ppucFrame = &pucMBTCPFrame[MB_TCP_FUNC];
+            *pusLength = usLength - MB_TCP_FUNC;
+            eStatus = MB_ENOERR;
+
+            /* Modbus TCP does not use any addresses. Fake the source address such
+             * that the processing part deals with this frame.
+             */
+            *pucRcvAddress = MB_TCP_PSEUDO_ADDRESS;
+        }
+    }
+    else
+    {
+        eStatus = MB_EIO;
+    }
+    return eStatus;
+}
+
+eMBErrorCode
+eMBTCPSend( UCHAR _unused, const UCHAR * pucFrame, USHORT usLength )
+{
+    eMBErrorCode    eStatus = MB_ENOERR;
+    UCHAR          *pucMBTCPFrame = ( UCHAR * ) pucFrame - MB_TCP_FUNC;
+    USHORT          usTCPLength = usLength + MB_TCP_FUNC;
+
+    /* The MBAP header is already initialized because the caller calls this
+     * function with the buffer returned by the previous call. Therefore we 
+     * only have to update the length in the header. Note that the length 
+     * header includes the size of the Modbus PDU and the UID Byte. Therefore 
+     * the length is usLength plus one.
+     */
+    pucMBTCPFrame[MB_TCP_LEN] = ( usLength + 1 ) >> 8U;
+    pucMBTCPFrame[MB_TCP_LEN + 1] = ( usLength + 1 ) & 0xFF;
+    if( xMBTCPPortSendResponse( pucMBTCPFrame, usTCPLength ) == FALSE )
+    {
+        eStatus = MB_EIO;
+    }
+    return eStatus;
+}
+
+#endif
diff --git a/apps/modbus/tcp/mbtcp.h b/apps/modbus/tcp/mbtcp.h
new file mode 100644
index 000000000..905d113c5
--- /dev/null
+++ b/apps/modbus/tcp/mbtcp.h
@@ -0,0 +1,53 @@
+/* 
+ * FreeModbus Libary: A portable Modbus implementation for Modbus ASCII/RTU.
+ * Copyright (c) 2006 Christian Walter <wolti@sil.at>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * File: $Id: mbtcp.h,v 1.2 2006/12/07 22:10:34 wolti Exp $
+ */
+
+#ifndef _MB_TCP_H
+#define _MB_TCP_H
+
+#ifdef __cplusplus
+PR_BEGIN_EXTERN_C
+#endif
+
+/* ----------------------- Defines ------------------------------------------*/
+#define MB_TCP_PSEUDO_ADDRESS   255
+
+/* ----------------------- Function prototypes ------------------------------*/
+    eMBErrorCode eMBTCPDoInit( USHORT ucTCPPort );
+void            eMBTCPStart( void );
+void            eMBTCPStop( void );
+eMBErrorCode    eMBTCPReceive( UCHAR * pucRcvAddress, UCHAR ** pucFrame,
+                               USHORT * pusLength );
+eMBErrorCode    eMBTCPSend( UCHAR _unused, const UCHAR * pucFrame,
+                            USHORT usLength );
+
+#ifdef __cplusplus
+PR_END_EXTERN_C
+#endif
+#endif