Add an infrastructure to support a generic quadrature encoder driver

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@4390 42af7a65-404d-4744-a932-0658087f49c3

10 files changed, 901 insertions, 8 deletions

diff --git a/nuttx/ChangeLog b/nuttx/ChangeLog
index 5404cbfe7..d957a193b 100644
--- a/nuttx/ChangeLog
+++ b/nuttx/ChangeLog
@@ -2460,3 +2460,9 @@
 	  can be used to turn debug output on and off.
 
 6.16 2012-xx-xx Gregory Nutt <gnutt@nuttx.org>
+
+	* drivers/sensors/qencoder.c and include/nuttx/sensors/qencoder.h:  Add an
+	  implementation for a quadrature encoder upper half driver.
+	* arch/arm/src/stm32/stm32_qencoder.c/.h:  Add a initial implementation of
+	  a lower-half quadrature encoder driver for the STM32.  On initial check-in,
+	  this is little more than a "skeleton" file.
diff --git a/nuttx/arch/arm/src/stm32/Make.defs b/nuttx/arch/arm/src/stm32/Make.defs
index 6306f2a26..213ac0be9 100644
--- a/nuttx/arch/arm/src/stm32/Make.defs
+++ b/nuttx/arch/arm/src/stm32/Make.defs
@@ -87,6 +87,10 @@ ifeq ($(CONFIG_PWM),y)
 CHIP_CSRCS	+= stm32_pwm.c
 endif
 
+ifeq ($(CONFIG_QENCODER),y)
+CHIP_CSRCS	+= stm32_qencoder.c
+endif
+
 ifeq ($(CONFIG_CAN),y)
 CHIP_CSRCS	+= stm32_can.c
 endif
diff --git a/nuttx/arch/arm/src/stm32/stm32_qencoder.c b/nuttx/arch/arm/src/stm32/stm32_qencoder.c
new file mode 100644
index 000000000..5b138b1d8
--- /dev/null
+++ b/nuttx/arch/arm/src/stm32/stm32_qencoder.c
@@ -0,0 +1,222 @@
+/************************************************************************************
+ * arch/arm/src/stm32/stm32_qencoder.c
+ *
+ *   Copyright (C) 2012 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *
+ * 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. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "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
+ * COPYRIGHT OWNER OR CONTRIBUTORS 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.
+ *
+ ************************************************************************************/
+
+/************************************************************************************
+ * Included Files
+ ************************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <stdint.h>
+#include <errno.h>
+
+#include <nuttx/arch.h>
+#include <nuttx/kmalloc.h>
+#include <nuttx/sensors/qencoder.h>
+
+#include "up_arch.h"
+#include "stm32_qencoder.h"
+
+#ifdef CONFIG_QENCODER
+
+/************************************************************************************
+ * Private Types
+ ************************************************************************************/
+
+struct stm32_lowerhalf_s
+{
+  /* The first field of this state structure must be a pointer to the lower-
+   * half callback structure:
+   */
+
+  FAR const struct qe_ops_s *ops;  /* Lower half callback structure */
+
+  /* STM32 driver-specific fields: */
+};
+
+/************************************************************************************
+ * Private Function Prototypes
+ ************************************************************************************/
+
+/* Lower-half Quadrature Encoder Driver Methods */
+
+static int stm32_setup(FAR struct qe_lowerhalf_s *lower);
+static int stm32_shutdown(FAR struct qe_lowerhalf_s *lower);
+static int stm32_position(FAR struct qe_lowerhalf_s *lower, int32_t *pos);
+static int stm32_reset(FAR struct qe_lowerhalf_s *lower);
+static int stm32_ioctl(FAR struct qe_lowerhalf_s *lower, int cmd, unsigned long arg);
+
+ /************************************************************************************
+ * Private Data
+ ************************************************************************************/
+/* The lower half callback structure */
+
+FAR const struct qe_ops_s g_qecallbacks =
+{
+  .setup    = stm32_setup,
+  .shutdown = stm32_shutdown,
+  .position = stm32_position,
+  .reset    = stm32_reset,
+  .ioctl    = stm32_ioctl,
+};
+
+/************************************************************************************
+ * Private Functions
+ ************************************************************************************/
+
+/************************************************************************************
+ * Name: stm32_setup
+ *
+ * Description:
+ *   This method is called when the driver is opened.  The lower half driver
+ *   should configure and initialize the device so that it is ready for use.
+ *   The initial position value should be zero. *   
+ *
+ ************************************************************************************/
+
+static int stm32_setup(FAR struct qe_lowerhalf_s *lower)
+{
+#warning "Missing logic"
+  return -ENOSYS;
+}
+
+/************************************************************************************
+ * Name: stm32_shutdown
+ *
+ * Description:
+ *   This method is called when the driver is closed.  The lower half driver
+ *   should stop data collection, free any resources, disable timer hardware, and
+ *   put the system into the lowest possible power usage state *   
+ *
+ ************************************************************************************/
+
+static int stm32_shutdown(FAR struct qe_lowerhalf_s *lower)
+{
+#warning "Missing logic"
+  return -ENOSYS;
+}
+
+/************************************************************************************
+ * Name: stm32_position
+ *
+ * Description:
+ *   Return the current position measurement.
+ *
+ ************************************************************************************/
+
+static int stm32_position(FAR struct qe_lowerhalf_s *lower, int32_t *pos)
+{
+#warning "Missing logic"
+  return -ENOSYS;
+}
+
+/************************************************************************************
+ * Name: stm32_reset
+ *
+ * Description:
+ *   Reset the position measurement to zero.
+ *
+ ************************************************************************************/
+
+static int stm32_reset(FAR struct qe_lowerhalf_s *lower)
+{
+#warning "Missing logic"
+  return -ENOSYS;
+}
+
+/************************************************************************************
+ * Name: stm32_ioctl
+ *
+ * Description:
+ *   Lower-half logic may support platform-specific ioctl commands
+ *
+ ************************************************************************************/
+
+static int stm32_ioctl(FAR struct qe_lowerhalf_s *lower, int cmd, unsigned long arg)
+{
+  /* No ioctl commands supported */
+
+  return -ENOTTY;
+}
+
+/************************************************************************************
+ * Public Functions
+ ************************************************************************************/
+
+/************************************************************************************
+ * Name: stm32_qeinitialize
+ *
+ * Description:
+ *   Initialize a quadrature encoder interface.  This function must be called from
+ *   board-specific logic after input pins have been configured.
+ *
+ * Input Parameters:
+ *   devpath - The full path to the driver to register. E.g., "/dev/qe0"
+ *
+ * Returned Values:
+ *   Zero on success; A negated errno value is returned on failure.
+ *
+ ************************************************************************************/
+
+int stm32_qeinitialize(FAR const char *devpath)
+{
+  FAR struct stm32_lowerhalf_s *lower;
+  int ret;
+
+  /* Allocate an instance to the device-specific, lower-half state structure */
+
+  lower = (FAR struct stm32_lowerhalf_s *)kmalloc(sizeof(struct stm32_lowerhalf_s));
+  if (lower)
+    {
+      return -ENOMEM;
+    }
+
+  /* Initialize the allocated state structure */
+
+  lower->ops = &g_qecallbacks;
+
+  /* Register the lower-half driver */
+
+  ret = qe_register(devpath, (FAR struct qe_lowerhalf_s *)lower);
+  if (ret < 0)
+    {
+      kfree(lower);
+      return ret;
+    }
+
+  return OK;
+}
+
+#endif /* CONFIG_QENCODER */
diff --git a/nuttx/arch/arm/src/stm32/stm32_qencoder.h b/nuttx/arch/arm/src/stm32/stm32_qencoder.h
new file mode 100644
index 000000000..5c977caad
--- /dev/null
+++ b/nuttx/arch/arm/src/stm32/stm32_qencoder.h
@@ -0,0 +1,72 @@
+/************************************************************************************
+ * arch/arm/src/stm32/stm32_qencoder.h
+ *
+ *   Copyright (C) 2012 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *
+ * 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. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "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
+ * COPYRIGHT OWNER OR CONTRIBUTORS 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.
+ *
+ ************************************************************************************/
+
+#ifndef __ARCH_ARM_SRC_STM32_STM32_QENCODER_H
+#define __ARCH_ARM_SRC_STM32_STM32_QENCODER_H
+
+/************************************************************************************
+ * Included Files
+ ************************************************************************************/
+
+#include <nuttx/config.h>
+
+#include "chip.h"
+
+#ifdef CONFIG_QENCODER
+
+/************************************************************************************
+ * Included Files
+ ************************************************************************************/
+
+/************************************************************************************
+ * Name: stm32_qeinitialize
+ *
+ * Description:
+ *   Initialize a quadrature encoder interface.  This function must be called from
+ *   board-specific logic after input pins have been configured.
+ *
+ * Input Parameters:
+ *   devpath - The full path to the driver to register. E.g., "/dev/qe0"
+ *
+ * Returned Values:
+ *   Zero on success; A negated errno value is returned on failure.
+ *
+ ************************************************************************************/
+
+int stm32_qeinitialize(FAR const char *devpath);
+
+#endif /* CONFIG_QENCODER */
+#endif /* __ARCH_ARM_SRC_STM32_STM32_QENCODER_H */
+
diff --git a/nuttx/drivers/sensors/Make.defs b/nuttx/drivers/sensors/Make.defs
index bda3e8ed3..bd28ba070 100644
--- a/nuttx/drivers/sensors/Make.defs
+++ b/nuttx/drivers/sensors/Make.defs
@@ -44,6 +44,12 @@ ifeq ($(CONFIG_I2C_LM75),y)
 endif
 endif
 
+# Quadrature encoder upper half
+
+ifeq ($(CONFIG_QENCODER),y)
+  CSRCS += qencoder.c
+endif
+
 # Include sensor driver build support
 
 DEPPATH += --dep-path sensors
diff --git a/nuttx/drivers/sensors/qencoder.c b/nuttx/drivers/sensors/qencoder.c
new file mode 100644
index 000000000..edbe8255c
--- /dev/null
+++ b/nuttx/drivers/sensors/qencoder.c
@@ -0,0 +1,396 @@
+/****************************************************************************
+ * drivers/sensors/qencoder.c
+ *
+ *   Copyright (C) 2012 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *
+ * 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. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "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
+ * COPYRIGHT OWNER OR CONTRIBUTORS 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.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Compilation Switches
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <sys/types.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <semaphore.h>
+#include <fcntl.h>
+#include <assert.h>
+#include <errno.h>
+#include <debug.h>
+
+#include <nuttx/fs.h>
+#include <nuttx/arch.h>
+#include <nuttx/sensors/qencoder.h>
+
+#include <arch/irq.h>
+
+#ifdef CONFIG_QENCODER
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+/* Debug ********************************************************************/
+/* Non-standard debug that may be enabled just for testing PWM */
+
+#ifdef CONFIG_DEBUG_QENCODER
+#  define qedbg    dbg
+#  define qevdbg   vdbg
+#  define qelldbg  lldbg
+#  define qellvdbg llvdbg
+#else
+#  define qedbg(x...)
+#  define qevdbg(x...)
+#  define qelldbg(x...)
+#  define qellvdbg(x...)
+#endif
+
+/****************************************************************************
+ * Private Type Definitions
+ ****************************************************************************/
+
+/* This structure describes the state of the upper half drivere */
+
+struct qe_upperhalf_s
+{
+  uint8_t                    crefs;    /* The number of times the device has been opened */
+  sem_t                      exclsem;  /* Supports mutual exclusion */
+  FAR struct qe_lowerhalf_s *lower;    /* lower-half state */
+};
+
+/****************************************************************************
+ * Private Function Prototypes
+ ****************************************************************************/
+
+static int     qe_open(FAR struct file *filep);
+static int     qe_close(FAR struct file *filep);
+static ssize_t qe_read(FAR struct file *filep, FAR char *buffer, size_t buflen);
+static ssize_t qe_write(FAR struct file *filep, FAR const char *buffer, size_t buflen);
+static int     qe_ioctl(FAR struct file *filep, int cmd, unsigned long arg);
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+static const struct file_operations g_qeops =
+{
+  qe_open,  /* open */
+  qe_close, /* close */
+  qe_read,  /* read */
+  qe_write, /* write */
+  0,         /* seek */
+  qe_ioctl  /* ioctl */
+#ifndef CONFIG_DISABLE_POLL
+  , 0        /* poll */
+#endif
+};
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/************************************************************************************
+ * Name: qe_open
+ *
+ * Description:
+ *   This function is called whenever the PWM device is opened.
+ *
+ ************************************************************************************/
+
+static int qe_open(FAR struct file *filep)
+{
+  FAR struct inode           *inode = filep->f_inode;
+  FAR struct qe_upperhalf_s *upper = inode->i_private;
+  uint8_t                     tmp;
+  int                         ret;
+
+  qevdbg("crefs: %d\n", upper->crefs);
+
+  /* Get exclusive access to the device structures */
+
+  ret = sem_wait(&upper->exclsem);
+  if (ret < 0)
+    {
+      ret = -errno;
+      goto errout;
+    }
+
+  /* Increment the count of references to the device.  If this the first
+   * time that the driver has been opened for this device, then initialize
+   * the device.
+   */
+
+  tmp = upper->crefs + 1;
+  if (tmp == 0)
+    {
+      /* More than 255 opens; uint8_t overflows to zero */
+
+      ret = -EMFILE;
+      goto errout_with_sem;
+    }
+
+  /* Check if this is the first time that the driver has been opened. */
+
+  if (tmp == 1)
+    {
+      FAR struct qe_lowerhalf_s *lower = upper->lower;
+
+      /* Yes.. perform one time hardware initialization. */
+
+      DEBUGASSERT(lower->ops->setup != NULL);
+      qevdbg("calling setup\n");
+
+      ret = lower->ops->setup(lower);
+      if (ret < 0)
+        {
+          goto errout_with_sem;
+        }
+    }
+
+  /* Save the new open count on success */
+
+  upper->crefs = tmp;
+  ret = OK;
+
+errout_with_sem:
+  sem_post(&upper->exclsem);
+  
+errout:
+  return ret;
+}
+
+/************************************************************************************
+ * Name: qe_close
+ *
+ * Description:
+ *   This function is called when the PWM device is closed.
+ *
+ ************************************************************************************/
+
+static int qe_close(FAR struct file *filep)
+{
+  FAR struct inode           *inode = filep->f_inode;
+  FAR struct qe_upperhalf_s *upper = inode->i_private;
+  int                         ret;
+
+  qevdbg("crefs: %d\n", upper->crefs);
+
+  /* Get exclusive access to the device structures */
+
+  ret = sem_wait(&upper->exclsem);
+  if (ret < 0)
+    {
+      ret = -errno;
+      goto errout;
+    }
+
+  /* Decrement the references to the driver.  If the reference count will
+   * decrement to 0, then uninitialize the driver.
+   */
+
+  if (upper->crefs > 1)
+    {
+      upper->crefs--;
+    }
+  else
+    {
+      FAR struct qe_lowerhalf_s *lower = upper->lower;
+
+      /* There are no more references to the port */
+
+      upper->crefs = 0;
+
+      /* Disable the PWM device */
+
+      DEBUGASSERT(lower->ops->shutdown != NULL);
+      qevdbg("calling shutdown: %d\n");
+
+      lower->ops->shutdown(lower);
+    }
+  ret = OK;
+
+//errout_with_sem:
+  sem_post(&upper->exclsem);
+  
+errout:
+  return ret;
+}
+
+/************************************************************************************
+ * Name: qe_read
+ *
+ * Description:
+ *   A dummy read method.  This is provided only to satsify the VFS layer.
+ *
+ ************************************************************************************/
+
+static ssize_t qe_read(FAR struct file *filep, FAR char *buffer, size_t buflen)
+{
+  /* Return zero -- usually meaning end-of-file */
+
+  return 0;
+}
+
+/************************************************************************************
+ * Name: qe_write
+ *
+ * Description:
+ *   A dummy write method.  This is provided only to satsify the VFS layer.
+ *
+ ************************************************************************************/
+
+static ssize_t qe_write(FAR struct file *filep, FAR const char *buffer, size_t buflen)
+{
+  /* Return a failure */
+
+  return -EPERM;
+}
+
+/************************************************************************************
+ * Name: qe_ioctl
+ *
+ * Description:
+ *   The standard ioctl method.  This is where ALL of the PWM work is done.
+ *   
+ ************************************************************************************/
+
+static int qe_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
+{
+  FAR struct inode          *inode = filep->f_inode;
+  FAR struct qe_upperhalf_s *upper = inode->i_private;
+  FAR struct qe_lowerhalf_s *lower = upper->lower;
+  int                        ret;
+
+  qevdbg("cmd: %d arg: %ld\n", cmd, arg);
+  DEBUGASSERT(upper && lower);
+
+  /* Get exclusive access to the device structures */
+
+  ret = sem_wait(&upper->exclsem);
+  if (ret < 0)
+    {
+      return ret;
+    }
+
+  /* Handle built-in ioctl commands */
+
+  switch (cmd)
+    {
+      /* QEIOC_POSITION - Get the current position from the encoder.
+       *   Argument: int32_t pointer to the location to return the position.
+       */
+
+      case QEIOC_POSITION:
+        {
+          FAR int32_t *ptr = (FAR int32_t *)((uintptr_t)arg);
+          DEBUGASSERT(lower->ops->position != NULL && ptr);
+          ret = lower->ops->position(lower, ptr);
+        }
+        break;
+
+      /* QEIOC_RESET - Reset the position to zero.
+       *   Argument: None
+       */
+
+      case QEIOC_RESET:
+        {
+          DEBUGASSERT(lower->ops->reset != NULL);
+          ret = lower->ops->reset(lower);
+        }
+        break;
+
+      /* Any unrecognized IOCTL commands might be platform-specific ioctl commands */
+
+      default:
+        {
+          qevdbg("Forwarding unrecognized cmd: %d arg: %ld\n", cmd, arg);
+          DEBUGASSERT(lower->ops->ioctl != NULL);
+          ret = lower->ops->ioctl(lower, cmd, arg);
+        }
+        break;
+    }
+
+  sem_post(&upper->exclsem);
+  return ret;
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: qe_register
+ *
+ * Description:
+ *   Register the Quadrature Encoder lower half device as 'devpath'
+ *
+ * Input Parameters:
+ *   devpath - The full path to the driver to register. E.g., "/dev/qe0"
+ *   lower - An instance of the lower half interface
+ *
+ * Returned Value:
+ *   Zero (OK) on success; a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+int qe_register(FAR const char *devpath, FAR struct qe_lowerhalf_s *lower)
+{
+  FAR struct qe_upperhalf_s *upper;
+
+  /* Allocate the upper-half data structure */
+
+  upper = (FAR struct qe_upperhalf_s *)zalloc(sizeof(struct qe_upperhalf_s));
+  if (!upper)
+    {
+      qedbg("Allocation failed\n");
+      return -ENOMEM;
+    }
+
+  /* Initialize the PWM device structure (it was already zeroed by zalloc()) */
+
+  sem_init(&upper->exclsem, 0, 1);
+  upper->lower = lower;
+
+  /* Register the PWM device */
+
+  qevdbg("Registering %s\n", devpath);
+  return register_driver(devpath, &g_qeops, 0666, upper);
+}
+
+#endif /* CONFIG_QENCODER */
diff --git a/nuttx/include/nuttx/ioctl.h b/nuttx/include/nuttx/ioctl.h
index b39bd65cb..c269b0772 100644
--- a/nuttx/include/nuttx/ioctl.h
+++ b/nuttx/include/nuttx/ioctl.h
@@ -65,6 +65,7 @@
 #define _PWMIOCBASE     (0x0c00) /* PWM ioctl commands */
 #define _CAIOCBASE      (0x0d00) /* CDC/ACM ioctl commands */
 #define _BATIOCBASE     (0x0e00) /* Battery driver ioctl commands */
+#define _QEIOCBASE      (0x0f00) /* Quadrature encoder ioctl commands */
 
 /* Macros used to manage ioctl commands */
 
@@ -193,6 +194,12 @@
 #define _BATIOCVALID(c)   (_IOC_TYPE(c)==_BATIOCBASE)
 #define _BATIOC(nr)       _IOC(_BATIOCBASE,nr)
 
+/* NuttX Quadrature Encoder driver ioctol definitions ***********************/
+/* (see nuttx/power/battery.h) */
+
+#define _QEIOCVALID(c)    (_IOC_TYPE(c)==_QEIOCBASE)
+#define _QEIOC(nr)        _IOC(_QEIOCBASE,nr)
+
 /****************************************************************************
  * Public Type Definitions
  ****************************************************************************/
diff --git a/nuttx/include/nuttx/pwm.h b/nuttx/include/nuttx/pwm.h
index acb65688b..3ebea1c13 100644
--- a/nuttx/include/nuttx/pwm.h
+++ b/nuttx/include/nuttx/pwm.h
@@ -81,7 +81,7 @@
 /* The PWM module uses a standard character driver framework.  However, since
  * the PWM driver is a devices control interface and not a data transfer
  * interface, the majority of the functionality is implemented in driver
- * ioctl calls.  The PWM ioctal commands are lised below:
+ * ioctl calls.  The PWM ioctl commands are lised below:
  *
  * PWMIOC_SETCHARACTERISTICS - Set the characteristics of the next pulsed
  *   output.  This command will neither start nor stop the pulsed output.
@@ -152,7 +152,7 @@ struct pwm_ops_s
   CODE int (*setup)(FAR struct pwm_lowerhalf_s *dev);
 
   /* This method is called when the driver is closed.  The lower half driver
-   * stop pulsed output, free any resources, disable the timer hardware, and
+   * should stop pulsed output, free any resources, disable the timer hardware, and
    * put the system into the lowest possible power usage state
    */
 
@@ -203,7 +203,7 @@ struct pwm_lowerhalf_s
   FAR const struct pwm_ops_s *ops;
 
   /* The custom timer state structure may include additional fields after
-   * the pointer to the PWM callback structgure.
+   * the pointer to the PWM callback structure.
    */
 };
 
diff --git a/nuttx/include/nuttx/sensors/lm75.h b/nuttx/include/nuttx/sensors/lm75.h
index 0d27a586b..43c90a466 100644
--- a/nuttx/include/nuttx/sensors/lm75.h
+++ b/nuttx/include/nuttx/sensors/lm75.h
@@ -1,8 +1,8 @@
 /****************************************************************************
  * include/nuttx/lm75.h
  *
- *   Copyright (C) 2011 Gregory Nutt. All rights reserved.
- *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *   Copyright (C) 2011-2012 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -33,8 +33,8 @@
  *
  ****************************************************************************/
 
-#ifndef __NUTTX_SENSORSD_LM75_H
-#define __NUTTX_SENSORSD_LM75_H
+#ifndef __NUTTX_SENSORS_LM75_H
+#define __NUTTX_SENSORS_LM75_H
 
 /****************************************************************************
  * Included Files
@@ -130,4 +130,4 @@ EXTERN int lm75_register(FAR const char *devpath, FAR struct i2c_dev_s *i2c,
 }
 #endif
 
-#endif /* __NUTTX_SENSORSD_LM75_H */
+#endif /* __NUTTX_SENSORS_LM75_H */
diff --git a/nuttx/include/nuttx/sensors/qencoder.h b/nuttx/include/nuttx/sensors/qencoder.h
new file mode 100644
index 000000000..b1ca83259
--- /dev/null
+++ b/nuttx/include/nuttx/sensors/qencoder.h
@@ -0,0 +1,180 @@
+/****************************************************************************
+ * include/nuttx/qencoder.h
+ *
+ *   Copyright (C) 2012 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *
+ * 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. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "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
+ * COPYRIGHT OWNER OR CONTRIBUTORS 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.
+ *
+ ****************************************************************************/
+
+#ifndef __NUTTX_SENSORS_QENCODER_H
+#define __NUTTX_SENSORS_QENCODER_H
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+#include <nuttx/ioctl.h>
+
+#ifdef CONFIG_QENCODER
+
+/****************************************************************************
+ * Pre-Processor Definitions
+ ****************************************************************************/
+/* Configuration ************************************************************
+ * CONFIG_QENCODER - Enables support for the quadrature encoder upper half
+ */
+
+/* IOCTL Commands ***********************************************************/
+/* The Quadrature Encode module uses a standard character driver framework. 
+ * However, since the driver is a devices control interface and not a data
+ * transfer interface, the majority of the functionality is implemented in
+ * driver ioctl calls.  The PWM ioctal commands are lised below:
+ *
+ * QEIOC_POSITION - Get the current position from the encoder.
+ *   Argument: int32_t pointer to the location to return the position.
+ * QEIOC_RESET - Reset the position to zero.
+ *   Argument: None
+ */
+
+#define QEIOC_POSITION     _QEIOC(0x0001) /* Arg: int32_t* pointer */
+#define QEIOC_RESET        _QEIOC(0x0002) /* Arg: None */
+
+/* User defined ioctl cms should use QEIOC_USER like this:
+ *
+ * #define QEIOC_MYCMD1    _QEIOC(QEIOC_USER)
+ * #define QEIOC_MYCMD2    _QEIOC(QEIOC_USER+1)
+ * ...
+ */
+
+#define QEIOC_USER         0x0003
+
+/****************************************************************************
+ * Public Types
+ ****************************************************************************/
+/* This is the vtable that is used to by the upper half quadrature encoder
+ * to call back into the lower half quadrature encoder.
+ */
+
+struct qe_lowerhalf_s;
+struct qe_ops_s
+{
+  /* This method is called when the driver is opened.  The lower half driver
+   * should configure and initialize the device so that it is ready for use.
+   * The initial position value should be zero.
+   */
+
+  CODE int (*setup)(FAR struct qe_lowerhalf_s *lower);
+
+  /* This method is called when the driver is closed.  The lower half driver
+   * should stop data collection, free any resources, disable timer hardware, and
+   * put the system into the lowest possible power usage state
+   */
+
+  CODE int (*shutdown)(FAR struct qe_lowerhalf_s *lower);
+
+  /* Return the current position measurement. */
+
+  CODE int (*position)(FAR struct qe_lowerhalf_s *lower, int32_t *pos);
+
+  /* Reset the position measurement to zero. */
+
+  CODE int (*reset)(FAR struct qe_lowerhalf_s *lower);
+
+  /* Lower-half logic may support platform-specific ioctl commands */
+
+  CODE int (*ioctl)(FAR struct qe_lowerhalf_s *lower,
+                    int cmd, unsigned long arg);
+};
+
+/* This is the interface between the lower half quadrature encoder driver
+ * and the upper half quadrature encoder driver.  A (device-specific)
+ * instance of this structure is passed to the upper-half driver when the
+ * quadrature encoder driver is registered.
+ *
+ * Normally that lower half logic will have its own, custom state structure
+ * that is simply cast to struct qe_lowerhalf_s.  In order to perform such casts,
+ * the initial fields of the custom state structure match the initial fields
+ * of the following generic lower half state structure.
+ */
+
+struct qe_lowerhalf_s
+{
+  /* The first field of this state structure must be a pointer to the lower-
+   * half callback structure:
+   */
+
+  FAR const struct qe_ops_s *ops;
+
+  /* The custom timer state structure may include additional fields after
+   * the pointer to the callback structure.
+   */
+
+};
+
+/****************************************************************************
+ * Public Data
+ ****************************************************************************/
+
+#ifdef __cplusplus
+#define EXTERN extern "C"
+extern "C" {
+#else
+#define EXTERN extern
+#endif
+
+/****************************************************************************
+ * Public Function Prototypes
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: qe_register
+ *
+ * Description:
+ *   Register the Quadrature Encoder lower half device as 'devpath'
+ *
+ * Input Parameters:
+ *   devpath - The full path to the driver to register. E.g., "/dev/qe0"
+ *   lower - An instance of the lower half interface
+ *
+ * Returned Value:
+ *   Zero (OK) on success; a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+EXTERN int qe_register(FAR const char *devpath, FAR struct qe_lowerhalf_s *lower);
+
+#undef EXTERN
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* CONFIG_QENCODER */
+#endif /* __NUTTX_SENSORS_QENCODER_H */