clean up of SPI bit bang logic

1 files changed, 610 insertions, 552 deletions

diff --git a/nuttx/include/nuttx/spi/spi_bitbang.c b/nuttx/include/nuttx/spi/spi_bitbang.c
index 8b1cee173..3aacc415c 100755
--- a/nuttx/include/nuttx/spi/spi_bitbang.c
+++ b/nuttx/include/nuttx/spi/spi_bitbang.c
@@ -1,552 +1,610 @@
-/****************************************************************************

- * configs/nuttx/spi/spi_bitbang.c

- *

- *   Copyright (C) 2013 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 <nuttx/spi/spi_bitbang.h>

-

-/****************************************************************************

- * Pre-processor Definitions

- ****************************************************************************/

-/* Usage ********************************************************************/

-/* To use this logic, you should provide a C file that does the following:

- *

- * - Defines SPI_SETSCK and SPI_CLRSCK to set and clear the SCK signal

- * - Defines SPI_SETMOSI and SPI_CLRMOSI to set and clear the MISO signal

- * - Defines SPI_GETMISO to sample the MISO state

- * - Defines SPI_PERBIT_NSEC which is the minimum time to transfer one bit.

- *   This determines the maximum frequency.

- * - Provide implementations of spi_select(), spi_status(), and spi_cmddata().

- * - Then include this file

- * - Provide an initialization function that initializes the GPIO pins used

- *   in the bit bang interface and calls spi_create_bitbang().

- */

-

-/* Debug ********************************************************************/

-/* Check if SPI debut is enabled (non-standard.. no support in

- * include/debug.h

- */

-

-#ifndef CONFIG_DEBUG

-#  undef CONFIG_DEBUG_VERBOSE

-#  undef CONFIG_DEBUG_SPI

-#endif

-

-#ifdef CONFIG_DEBUG_SPI

-#  define spidbg lldbg

-#  ifdef CONFIG_DEBUG_VERBOSE

-#    define spivdbg lldbg

-#  else

-#    define spivdbg(x...)

-#  endif

-#else

-#  define spidbg(x...)

-#  define spivdbg(x...)

-#endif

-

-/****************************************************************************

- * Private Types

- ****************************************************************************/

-

-/****************************************************************************

- * Private Function Prototypes

- ****************************************************************************/

-

-static void     spi_select(FAR struct spi_bitbang_s *priv,

-                  enum spi_dev_e devid, bool selected);

-static uint32_t spi_setfrequency(FAR struct spi_bitbang_s *priv,

-                  uint32_t frequency);

-static void     spi_setmode(FAR struct spi_bitbang_s *priv,

-                  enum spi_mode_e mode);

-static uint16_t spi_bitexchange0(FAR struct spi_bitbang_s *priv,

-                  uint16_t dataout);

-static uint16_t spi_bitexchange1(FAR struct spi_bitbang_s *priv,

-                  uint16_t dataout);

-static uint16_t spi_bitexchange2(FAR struct spi_bitbang_s *priv,

-                  uint16_t dataout);

-static uint16_t spi_bitexchange3(FAR struct spi_bitbang_s *priv,

-                  uint16_t dataout);

-static uint16_t spi_exchange(FAR struct spi_bitbang_s *priv,

-                  uint16_t dataout);

-static uint8_t  spi_status(FAR struct spi_bitbang_s *priv,

-                  enum spi_dev_e devid);

-#ifdef CONFIG_SPI_CMDDATA

-static int      spi_cmddata(FAR struct spi_bitbang_s *priv,

-                  enum spi_dev_e devid, bool cmd);

-#endif

-

-/****************************************************************************

- * Private Data

- ****************************************************************************/

-

-static const struct spi_bitbang_ops_s g_spiops =

-{

-  spi_select,        /* select */

-  spi_setfrequency,  /* setfrequency */

-  spi_setmode,       /* setmode */

-  spi_exchange,      /* exchange */

-  spi_status,        /* status */

-#ifdef CONFIG_SPI_CMDDATA

-  spi_cmddata,       /* cmddata */

-#endif

-};

-

-/****************************************************************************

- * Private Functions

- ****************************************************************************/

- /****************************************************************************

- * Name: spi_setfrequency

- *

- * Description:

- *   Set the SPI frequency.

- *

- * Input Parameters:

- *   dev -       Device-specific state data

- *   frequency - The SPI frequency requested

- *

- * Returned Value:

- *   Returns the actual frequency selected

- *

- ****************************************************************************/

-

-static uint32_t spi_setfrequency(FAR struct spi_bitbang_s *priv, uint32_t frequency)

-{

-  uint32_t pnsec;

-

-  /* SPI frequency cannot be precisely controlled with a bit-bang interface.

-   * Freqency corresponds to delay in toggle the SPI clock line:  Set high,

-   * wait, set low, wait, set high, wait, etc.

-   *

-   * Here we calcalute the half period of the frequency in nanoseconds (i.e.,

-   * the amount of time that the clock should remain in the high or low state).

-   *

-   *   frequency = psec / 1 sec                       psec = full period in seconds

-   *   psec      = 1 sec / frequency

-   *   pnsec     = 1000000000 nsec / (2 * frequency)  pnsec = full period in nsec

-   *

-   * As examples:

-   * 1) frequency = 400KHz; SPI_PERBIT_NSEC = 100

-   *    pnsec     = 2500 - 100 = 2400

-   *    holdtime  = ((2401) >> 1) + 500) / 1000 = 1

-   * 2) frequency = 20MHz;  SPI_PERBIT_NSEC = 100

-   *    pnsec     = 50 - 100 -> 0

-   *    holdtime  = ((0) >> 1) + 500) / 1000 = 0

-   */

-

-  pnsec = (1000000000ul + (frequency >> 1)) / frequency;

-

-  /* Minus the bit transfer overhead */

-

-  if (pnsec > SPI_PERBIT_NSEC)

-    {

-      pnsec -= SPI_PERBIT_NSEC;

-    }

-  else

-    {

-      pnsec = 0;

-    }

-

-  /* The hold time in microseconds is half of this (in microseconds) */

-

-  priv->holdtime =  (((pnsec + 1) >> 1) + 500) / 1000;

-

-  /* Let's do our best to calculate the actual frequency

-   *

-   * As examples:

-   * 1) frequency = 400KHz; SPI_PERBIT_NSEC = 100; holdtime = 1

-   *    pnsec     = 2000 * 1 + 100 = 2100

-   *    frequency = 476KHz

-   * 2) frequency = 20MHz;  SPI_PERBIT_NSEC = 100; holdtime = 0

-   *    pnsec     = 2000 * 0 + 100 = 100

-   *    frequency = 10MHz

-   */

-

-  pnsec = 2000 * priv->holdtime + SPI_PERBIT_NSEC;

-  frequency = 1000000000ul / pnsec;

-  return frequency;

-}

-

-/****************************************************************************

- * Name: spi_setmode

- *

- * Description:

- *   Select the current SPI mode

- *

- * Input Parameters:

- *   dev  - Device-specific state data

- *   mode - the new SPI mode

- *

- * Returned Value:

- *   None

- *

- ****************************************************************************/

-

-static void spi_setmode(FAR struct spi_bitbang_s *priv,

-                        enum spi_mode_e mode)

-{

-  spivdbg("mode=%d\n", mode);

-

-  switch (mode)

-    {

-    case SPIDEV_MODE0: /* CPOL=0; CPHA=0 */

-#ifndef CONFIG_SPI_BITBANG_DISABLEMODE0

-      SPI_CLRSCK;      /* Resting level of the clock is low */

-      priv->exchange = spi_bitexchange0;

-#else

-      DEBUGPANIC();

-#endif

-      break;

-

-    case SPIDEV_MODE1: /* CPOL=0; CPHA=1 */

-#ifndef CONFIG_SPI_BITBANG_DISABLEMODE1

-      SPI_CLRSCK;      /* Resting level of the clock is low */

-      priv->exchange = spi_bitexchange1;

-#else

-      DEBUGPANIC();

-#endif

-      break;

-

-    case SPIDEV_MODE2: /* CPOL=1; CPHA=0 */

-#ifndef CONFIG_SPI_BITBANG_DISABLEMODE2

-      SPI_SETSCK;      /* Resting level of the clock is high */

-      priv->exchange = spi_bitexchange2;

-#else

-      DEBUGPANIC();

-#endif

-      break;

-

-    case SPIDEV_MODE3: /* CPOL=1; CPHA=1 */

-#ifndef CONFIG_SPI_BITBANG_DISABLEMODE3

-      SPI_SETSCK;      /* Resting level of the clock is high */

-      priv->exchange = spi_bitexchange3;

-#else

-      DEBUGPANIC();

-#endif

-      break;

-

-    default:

-      DEBUGPANIC();

-      break;

-    }

-}

-

-/****************************************************************************

- * Name: spi_bitexchange0

- *

- * Description:

- *   Exchange one bit in mode 0

- *

- * Input Parameters:

- *   dev  - Device-specific state data

- *   lock - true: Lock spi bus, false: unlock SPI bus

- *

- * Returned Value:

- *   None

- *

- ****************************************************************************/

-

-#ifndef CONFIG_SPI_BITBANG_DISABLEMODE0

-static uint16_t spi_bitexchange0(FAR struct spi_bitbang_s *priv,

-                                 uint16_t dataout)

-{

-  uint16_t datain;

-                                   /* No clock transition before setting MOSI */

-  if (dataout != 0)

-    {

-      SPI_SETMOSI;                /* Set MISO if the bit is set */

-    }

-  else

-    {

-      SPI_CLRMOSI;                /* Clear MISO if the bit is not set */

-    }

-

-  SPI_SETSCK;                     /* Clock transition before getting MISO */

-  datain = (uint16_t)SPI_GETMISO; /* Get bit 0 = MOSI value */

-  if (priv->holdtime)

-    {

-      up_udelay(priv->holdtime);

-    }

-

-  SPI_CLRSCK;                     /* Return clock to the resting state after getting MISO */

-  if (priv->holdtime)

-    {

-      up_udelay(priv->holdtime);

-    }

-

-  return datain;

-}

-#endif

-

-/****************************************************************************

- * Name: spi_bitexchange1

- *

- * Description:

- *   Exchange one bit in mode 1

- *

- * Input Parameters:

- *   dev  - Device-specific state data

- *   lock - true: Lock spi bus, false: unlock SPI bus

- *

- * Returned Value:

- *   None

- *

- ****************************************************************************/

-

-#ifndef CONFIG_SPI_BITBANG_DISABLEMODE1

-static uint16_t spi_bitexchange1(FAR struct spi_bitbang_s *priv,

-                                uint16_t dataout)

-{

-  uint16_t datain;

-

-  SPI_SETSCK;                     /* Clock transition before setting MOSI */

-  if (dataout != 0)

-    {

-      SPI_SETMOSI;                /* Set MISO if the bit is set */

-    }

-  else

-    {

-      SPI_CLRMOSI;                /* Clear MISO if the bit is not set */

-    }

-

-  if (priv->holdtime)

-    {

-      up_udelay(priv->holdtime);

-    }

-

-  SPI_CLRSCK;                     /* Clock transition before getting MISO */

-  datain = (uint16_t)SPI_GETMISO; /* Get bit 0 = MOSI value */

-                                  /* Clock is in resting state after getting MISO */

-  if (priv->holdtime)

-    {

-      up_udelay(priv->holdtime);

-    }

-

-  return datain;

-}

-#endif

-

-/****************************************************************************

- * Name: spi_bitexchange2

- *

- * Description:

- *   Exchange one bit in mode 2

- *

- * Input Parameters:

- *   dev  - Device-specific state data

- *   lock - true: Lock spi bus, false: unlock SPI bus

- *

- * Returned Value:

- *   None

- *

- ****************************************************************************/

-

-#ifndef CONFIG_SPI_BITBANG_DISABLEMODE2

-static uint16_t spi_bitexchange2(FAR struct spi_bitbang_s *priv,

-                                 uint16_t dataout)

-{

-  uint16_t datain;

-                                  /* No clock transition before setting MOSI */

-  if (dataout != 0)

-    {

-      SPI_SETMOSI;                /* Set MISO if the bit is set */

-    }

-  else

-    {

-      SPI_CLRMOSI;                /* Clear MISO if the bit is not set */

-    }

-

-  SPI_CLRSCK;                     /* Clock transition before getting MISO */

-  datain = (uint16_t)SPI_GETMISO; /* Get bit 0 = MOSI value */

-  if (priv->holdtime)

-    {

-      up_udelay(priv->holdtime);

-    }

-

-  SPI_SETSCK;                     /* Return clock to the resting state after getting MISO */

-  if (priv->holdtime)

-    {

-      up_udelay(priv->holdtime);

-    }

-

-  return datain;

-}

-#endif

-

-/****************************************************************************

- * Name: spi_bitexchange3

- *

- * Description:

- *   Exchange one bit in mode 3

- *

- * Input Parameters:

- *   dev  - Device-specific state data

- *   lock - true: Lock spi bus, false: unlock SPI bus

- *

- * Returned Value:

- *   None

- *

- ****************************************************************************/

-

-#ifndef CONFIG_SPI_BITBANG_DISABLEMODE3

-static uint16_t spi_bitexchange3(FAR struct spi_bitbang_s *priv,

-                                 uint16_t dataout)

-{

-  uint16_t datain;

-

-  SPI_CLRSCK;                     /* Clock transition before setting MOSI */

-  if (dataout != 0)

-    {

-      SPI_SETMOSI;                /* Set MISO if the bit is set */

-    }

-  else

-    {

-      SPI_CLRMOSI;                /* Clear MISO if the bit is not set */

-    }

-

-  if (priv->holdtime)

-    {

-      up_udelay(priv->holdtime);

-    }

-

-  SPI_SETSCK;                     /* Clock transition before getting MISO */

-  datain = (uint16_t)SPI_GETMISO; /* Get bit 0 = MOSI value */

-                                  /* Clock is in resting state after getting MISO */

-  if (priv->holdtime)

-    {

-      up_udelay(priv->holdtime);

-    }

-

-  return datain;

-}

-#endif

-

-/****************************************************************************

- * Name: spi_exchange

- *

- * Description:

- *   Exahange on word of data on SPI

- *

- * Input Parameters:

- *   priv     - Device-specific state data

- *   data     - The TX data to be exchanged with the slave

- *

- * Returned Value:

- *   The RX data received from the slave

- *

- ****************************************************************************/

-

-#ifdef CONFIG_SPI_BITBANG_VARWIDTH

-static uint16_t spi_exchange(FAR struct spi_bitbang_s *priv, uint16_t dataout)

-{

-  uint16_t datain;

-  uint16_t bit;

-  int shift;

-

-  /* Transfer each bit.  This might be better done with straight-line

-   * logic because the loop overhead will limit our maximum transfer

-   * rate.

-   */

-

-  shift =  priv->nbits - 1

-  for (bit = 1 << shift; bit != 0; bit >>= 1)

-    {

-      /* Shift to make space for the next, less significant bit.

-       * Then exchange bits with the slave an OR in the new, returned

-       * bit.

-       */

-

-      datain <<= 1;

-      datain |= priv->exchange(priv, dataout & bit);

-    }

-

-  return datain;

-}

-

-#else

-static uint16_t spi_exchange(FAR struct spi_bitbang_s *priv, uint16_t dataout)

-{

-  uint8_t datain;

-

-  /* Transfer each bit.  This is better done with straight-line logic

-   * when possible because the loop overhead will limit our maximum transfer

-   * rate.

-   */

-

-  /* Exchange bit 7 with the slave */

-

-  datain = priv->exchange(priv, dataout & (1 << 7));

-

-  /* Exchange bit 6 with the slave */

-

-  datain <<= 1;

-  datain |= priv->exchange(priv, dataout & (1 << 6));

-

-  /* Exchange bit 5 with the slave */

-

-  datain <<= 1;

-  datain |= priv->exchange(priv, dataout & (1 << 5));

-

-  /* Exchange bit 4 with the slave */

-

-  datain <<= 1;

-  datain |= priv->exchange(priv, dataout & (1 << 4));

-

-  /* Exchange bit 3 with the slave */

-

-  datain <<= 1;

-  datain |= priv->exchange(priv, dataout & (1 << 3));

-

-  /* Exchange bit 2 with the slave */

-

-  datain <<= 1;

-  datain |= priv->exchange(priv, dataout & (1 << 2));

-

-  /* Exchange bit 1 with the slave */

-

-  datain <<= 1;

-  datain |= priv->exchange(priv, dataout & (1 << 1));

-

-  /* Exchange bit 0 with the slave */

-

-  datain <<= 1;

-  datain |= priv->exchange(priv, dataout & (1 << 0));

-

-  return datain;

-}

-#endif

+/****************************************************************************
+ * configs/nuttx/spi/spi_bitbang.c
+ *
+ *   Copyright (C) 2013 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 <nuttx/spi/spi_bitbang.h>
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+/* Usage ********************************************************************/
+/* To use this logic, you should provide a C file that does the following:
+ *
+ * - Defines SPI_SETSCK and SPI_CLRSCK to set and clear the SCK signal
+ * - Defines SPI_SETMOSI and SPI_CLRMOSI to set and clear the MISO signal
+ * - Defines SPI_GETMISO to sample the MISO state
+ * - Defines SPI_PERBIT_NSEC which is the minimum time to transfer one bit.
+ *   This determines the maximum frequency.
+ * - Other configuration options:
+ *   SPI_BITBANG_DISABLEMODE0 - Define to disable Mode 0 support
+ *   SPI_BITBANG_DISABLEMODE1 - Define to disable Mode 1 support
+ *   SPI_BITBANG_DISABLEMODE2 - Define to disable Mode 2 support
+ *   SPI_BITBANG_DISABLEMODE3 - Define to disable Mode 3 support
+ * - Provide implementations of spi_select(), spi_status(), and spi_cmddata().
+ * - Then include this file
+ * - Provide an initialization function that initializes the GPIO pins used
+ *   in the bit bang interface and calls spi_create_bitbang().
+ */
+
+/* Debug ********************************************************************/
+/* Check if SPI debut is enabled (non-standard.. no support in
+ * include/debug.h
+ */
+
+#ifndef CONFIG_DEBUG
+#  undef CONFIG_DEBUG_VERBOSE
+#  undef CONFIG_DEBUG_SPI
+#endif
+
+#ifdef CONFIG_DEBUG_SPI
+#  define spidbg lldbg
+#  ifdef CONFIG_DEBUG_VERBOSE
+#    define spivdbg lldbg
+#  else
+#    define spivdbg(x...)
+#  endif
+#else
+#  define spidbg(x...)
+#  define spivdbg(x...)
+#endif
+
+/****************************************************************************
+ * Private Types
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Function Prototypes
+ ****************************************************************************/
+
+static void     spi_select(FAR struct spi_bitbang_s *priv,
+                  enum spi_dev_e devid, bool selected);
+static uint32_t spi_setfrequency(FAR struct spi_bitbang_s *priv,
+                  uint32_t frequency);
+static void     spi_setmode(FAR struct spi_bitbang_s *priv,
+                  enum spi_mode_e mode);
+static uint16_t spi_bitexchange0(FAR struct spi_bitbang_s *priv,
+                  uint16_t dataout);
+static uint16_t spi_bitexchange1(FAR struct spi_bitbang_s *priv,
+                  uint16_t dataout);
+static uint16_t spi_bitexchange2(FAR struct spi_bitbang_s *priv,
+                  uint16_t dataout);
+static uint16_t spi_bitexchange3(FAR struct spi_bitbang_s *priv,
+                  uint16_t dataout);
+static uint16_t spi_exchange(FAR struct spi_bitbang_s *priv,
+                  uint16_t dataout);
+static uint8_t  spi_status(FAR struct spi_bitbang_s *priv,
+                  enum spi_dev_e devid);
+#ifdef CONFIG_SPI_CMDDATA
+static int      spi_cmddata(FAR struct spi_bitbang_s *priv,
+                  enum spi_dev_e devid, bool cmd);
+#endif
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+static const struct spi_bitbang_ops_s g_spiops =
+{
+  spi_select,        /* select */
+  spi_setfrequency,  /* setfrequency */
+  spi_setmode,       /* setmode */
+  spi_exchange,      /* exchange */
+  spi_status,        /* status */
+#ifdef CONFIG_SPI_CMDDATA
+  spi_cmddata,       /* cmddata */
+#endif
+};
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+ /****************************************************************************
+ * Name: spi_setfrequency
+ *
+ * Description:
+ *   Set the SPI frequency.
+ *
+ * Input Parameters:
+ *   dev -       Device-specific state data
+ *   frequency - The SPI frequency requested
+ *
+ * Returned Value:
+ *   Returns the actual frequency selected
+ *
+ ****************************************************************************/
+
+static uint32_t spi_setfrequency(FAR struct spi_bitbang_s *priv, uint32_t frequency)
+{
+  uint32_t pnsec;
+
+  /* SPI frequency cannot be precisely controlled with a bit-bang interface.
+   * Freqency corresponds to delay in toggle the SPI clock line:  Set high,
+   * wait, set low, wait, set high, wait, etc.
+   *
+   * Here we calcalute the half period of the frequency in nanoseconds (i.e.,
+   * the amount of time that the clock should remain in the high or low state).
+   *
+   *   frequency = psec / 1 sec                       psec = full period in seconds
+   *   psec      = 1 sec / frequency
+   *   pnsec     = 1000000000 nsec / (2 * frequency)  pnsec = full period in nsec
+   *
+   * As examples:
+   * 1) frequency = 400KHz; SPI_PERBIT_NSEC = 100
+   *    pnsec     = 2500 - 100 = 2400
+   *    holdtime  = ((2401) >> 1) + 500) / 1000 = 1
+   * 2) frequency = 20MHz;  SPI_PERBIT_NSEC = 100
+   *    pnsec     = 50 - 100 -> 0
+   *    holdtime  = ((0) >> 1) + 500) / 1000 = 0
+   */
+
+  pnsec = (1000000000ul + (frequency >> 1)) / frequency;
+
+  /* Minus the bit transfer overhead */
+
+  if (pnsec > SPI_PERBIT_NSEC)
+    {
+      pnsec -= SPI_PERBIT_NSEC;
+    }
+  else
+    {
+      pnsec = 0;
+    }
+
+  /* The hold time in microseconds is half of this (in microseconds) */
+
+  priv->holdtime =  (((pnsec + 1) >> 1) + 500) / 1000;
+
+  /* Let's do our best to calculate the actual frequency
+   *
+   * As examples:
+   * 1) frequency = 400KHz; SPI_PERBIT_NSEC = 100; holdtime = 1
+   *    pnsec     = 2000 * 1 + 100 = 2100
+   *    frequency = 476KHz
+   * 2) frequency = 20MHz;  SPI_PERBIT_NSEC = 100; holdtime = 0
+   *    pnsec     = 2000 * 0 + 100 = 100
+   *    frequency = 10MHz
+   */
+
+  pnsec = 2000 * priv->holdtime + SPI_PERBIT_NSEC;
+  frequency = 1000000000ul / pnsec;
+  return frequency;
+}
+
+/****************************************************************************
+ * Name: spi_setmode
+ *
+ * Description:
+ *   Select the current SPI mode
+ *
+ * Input Parameters:
+ *   dev  - Device-specific state data
+ *   mode - the new SPI mode
+ *
+ * Returned Value:
+ *   None
+ *
+ ****************************************************************************/
+
+static void spi_setmode(FAR struct spi_bitbang_s *priv,
+                        enum spi_mode_e mode)
+{
+  spivdbg("mode=%d\n", mode);
+
+  switch (mode)
+    {
+    case SPIDEV_MODE0: /* CPOL=0; CPHA=0 */
+#ifndef SPI_BITBANG_DISABLEMODE0
+      SPI_CLRSCK;      /* Resting level of the clock is low */
+      priv->exchange = spi_bitexchange0;
+#else
+      DEBUGPANIC();
+#endif
+      break;
+
+    case SPIDEV_MODE1: /* CPOL=0; CPHA=1 */
+#ifndef SPI_BITBANG_DISABLEMODE1
+      SPI_CLRSCK;      /* Resting level of the clock is low */
+      priv->exchange = spi_bitexchange1;
+#else
+      DEBUGPANIC();
+#endif
+      break;
+
+    case SPIDEV_MODE2: /* CPOL=1; CPHA=0 */
+#ifndef SPI_BITBANG_DISABLEMODE2
+      SPI_SETSCK;      /* Resting level of the clock is high */
+      priv->exchange = spi_bitexchange2;
+#else
+      DEBUGPANIC();
+#endif
+      break;
+
+    case SPIDEV_MODE3: /* CPOL=1; CPHA=1 */
+#ifndef SPI_BITBANG_DISABLEMODE3
+      SPI_SETSCK;      /* Resting level of the clock is high */
+      priv->exchange = spi_bitexchange3;
+#else
+      DEBUGPANIC();
+#endif
+      break;
+
+    default:
+      DEBUGPANIC();
+      break;
+    }
+}
+
+/****************************************************************************
+ * Name: spi_bitexchange0
+ *
+ * Description:
+ *   Exchange one bit in mode 0
+ *
+ *   MODE 0: CPOL=0 and CPHA = 0
+ *   The base value of the clock is zero.  Data is captured on the clock's
+ *   rising edge and data is propagated on the falling edge (high->low
+ *   transition).
+ *
+ *         hold time
+ *       +------------+
+ *       |            | hold time
+ *  -----+            +------------
+ *    |   |           `- Propagate to next bit
+ *    |   |
+ *    |   `- MISO sampled
+ *    ` Set MOSI
+ *
+ * Input Parameters:
+ *   dev  - Device-specific state data
+ *   lock - true: Lock spi bus, false: unlock SPI bus
+ *
+ * Returned Value:
+ *   None
+ *
+ ****************************************************************************/
+
+#ifndef SPI_BITBANG_DISABLEMODE0
+static uint16_t spi_bitexchange0(FAR struct spi_bitbang_s *priv,
+                                 uint16_t dataout)
+{
+  uint16_t datain;
+                                   /* No clock transition before setting MOSI */
+  if (dataout != 0)
+    {
+      SPI_SETMOSI;                /* Set MISO if the bit is set */
+    }
+  else
+    {
+      SPI_CLRMOSI;                /* Clear MISO if the bit is not set */
+    }
+
+  SPI_SETSCK;                     /* Clock transition before getting MISO */
+  datain = (uint16_t)SPI_GETMISO; /* Get bit 0 = MOSI value */
+  if (priv->holdtime)
+    {
+      up_udelay(priv->holdtime);
+    }
+
+  SPI_CLRSCK;                     /* Return clock to the resting state after getting MISO */
+  if (priv->holdtime)
+    {
+      up_udelay(priv->holdtime);
+    }
+
+  return datain;
+}
+#endif
+
+/****************************************************************************
+ * Name: spi_bitexchange1
+ *
+ * Description:
+ *   Exchange one bit in mode 1
+ *
+ *   MODE 1: CPOL=0 and CPHA = 1
+ *   The base value of the clock is zero.  Data is captured on the clock's
+ *   falling edge and data is propagated on the rising edge
+ *
+ *         hold time
+ *       +------------+
+ *       |            | hold time
+ *  -----+            +------------
+ *        |           | `- MISO sampled
+ *        |           |
+ *        |           `- Propagate to next bit
+ *        ` Set MOSI
+ *
+ * Input Parameters:
+ *   dev  - Device-specific state data
+ *   lock - true: Lock spi bus, false: unlock SPI bus
+ *
+ * Returned Value:
+ *   None
+ *
+ ****************************************************************************/
+
+#ifndef SPI_BITBANG_DISABLEMODE1
+static uint16_t spi_bitexchange1(FAR struct spi_bitbang_s *priv,
+                                uint16_t dataout)
+{
+  uint16_t datain;
+
+  SPI_SETSCK;                     /* Clock transition before setting MOSI */
+  if (dataout != 0)
+    {
+      SPI_SETMOSI;                /* Set MISO if the bit is set */
+    }
+  else
+    {
+      SPI_CLRMOSI;                /* Clear MISO if the bit is not set */
+    }
+
+  if (priv->holdtime)
+    {
+      up_udelay(priv->holdtime);
+    }
+
+  SPI_CLRSCK;                     /* Clock transition before getting MISO */
+  datain = (uint16_t)SPI_GETMISO; /* Get bit 0 = MOSI value */
+                                  /* Clock is in resting state after getting MISO */
+  if (priv->holdtime)
+    {
+      up_udelay(priv->holdtime);
+    }
+
+  return datain;
+}
+#endif
+
+/****************************************************************************
+ * Name: spi_bitexchange2
+ *
+ * Description:
+ *   Exchange one bit in mode 2
+ *
+ *   MODE 2: CPOL=1 and CPHA = 0
+ *     The base value of the clock is one.  Data is captured on the clock's
+ *     falling edge and data is propagated on the rising edge.
+ *
+ *         hold time
+ *  -----+            +------------
+ *       |            | hold time
+ *       +------------+
+ *      |  |          `- Propagate to next bit
+ *      |  |
+ *      |  `- MISO sampled
+ *       ` Set MOSI
+ *
+ * Input Parameters:
+ *   dev  - Device-specific state data
+ *   lock - true: Lock spi bus, false: unlock SPI bus
+ *
+ * Returned Value:
+ *   None
+ *
+ ****************************************************************************/
+
+#ifndef SPI_BITBANG_DISABLEMODE2
+static uint16_t spi_bitexchange2(FAR struct spi_bitbang_s *priv,
+                                 uint16_t dataout)
+{
+  uint16_t datain;
+                                  /* No clock transition before setting MOSI */
+  if (dataout != 0)
+    {
+      SPI_SETMOSI;                /* Set MISO if the bit is set */
+    }
+  else
+    {
+      SPI_CLRMOSI;                /* Clear MISO if the bit is not set */
+    }
+
+  SPI_CLRSCK;                     /* Clock transition before getting MISO */
+  datain = (uint16_t)SPI_GETMISO; /* Get bit 0 = MOSI value */
+  if (priv->holdtime)
+    {
+      up_udelay(priv->holdtime);
+    }
+
+  SPI_SETSCK;                     /* Return clock to the resting state after getting MISO */
+  if (priv->holdtime)
+    {
+      up_udelay(priv->holdtime);
+    }
+
+  return datain;
+}
+#endif
+
+/****************************************************************************
+ * Name: spi_bitexchange3
+ *
+ * Description:
+ *   Exchange one bit in mode 3
+ *
+ *   MODE 3: CPOL=1 and CPHA = 1
+ *     The base value of the clock is one.  Data is captured on the clock's
+ *     rising edge and data is propagated on the falling edge.
+ *
+ *         hold time
+ *  -----+            +------------
+ *       |            | hold time
+ *       +------------+
+ *        |           | `- MISO sampled
+ *        |           |
+ *        |           `- Propagate to next bit
+ *         ` Set MOSI
+ *
+ * Input Parameters:
+ *   dev  - Device-specific state data
+ *   lock - true: Lock spi bus, false: unlock SPI bus
+ *
+ * Returned Value:
+ *   None
+ *
+ ****************************************************************************/
+
+#ifndef SPI_BITBANG_DISABLEMODE3
+static uint16_t spi_bitexchange3(FAR struct spi_bitbang_s *priv,
+                                 uint16_t dataout)
+{
+  uint16_t datain;
+
+  SPI_CLRSCK;                     /* Clock transition before setting MOSI */
+  if (dataout != 0)
+    {
+      SPI_SETMOSI;                /* Set MISO if the bit is set */
+    }
+  else
+    {
+      SPI_CLRMOSI;                /* Clear MISO if the bit is not set */
+    }
+
+  if (priv->holdtime)
+    {
+      up_udelay(priv->holdtime);
+    }
+
+  SPI_SETSCK;                     /* Clock transition before getting MISO */
+  datain = (uint16_t)SPI_GETMISO; /* Get bit 0 = MOSI value */
+                                  /* Clock is in resting state after getting MISO */
+  if (priv->holdtime)
+    {
+      up_udelay(priv->holdtime);
+    }
+
+  return datain;
+}
+#endif
+
+/****************************************************************************
+ * Name: spi_exchange
+ *
+ * Description:
+ *   Exahange on word of data on SPI
+ *
+ * Input Parameters:
+ *   priv     - Device-specific state data
+ *   data     - The TX data to be exchanged with the slave
+ *
+ * Returned Value:
+ *   The RX data received from the slave
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_SPI_BITBANG_VARWIDTH
+static uint16_t spi_exchange(FAR struct spi_bitbang_s *priv, uint16_t dataout)
+{
+  uint16_t datain;
+  uint16_t bit;
+  int shift;
+
+  /* Transfer each bit.  This might be better done with straight-line
+   * logic because the loop overhead will limit our maximum transfer
+   * rate.
+   */
+
+  shift =  priv->nbits - 1
+  for (bit = 1 << shift; bit != 0; bit >>= 1)
+    {
+      /* Shift to make space for the next, less significant bit.
+       * Then exchange bits with the slave an OR in the new, returned
+       * bit.
+       */
+
+      datain <<= 1;
+      datain |= priv->exchange(priv, dataout & bit);
+    }
+
+  return datain;
+}
+
+#else
+static uint16_t spi_exchange(FAR struct spi_bitbang_s *priv, uint16_t dataout)
+{
+  uint8_t datain;
+
+  /* Transfer each bit.  This is better done with straight-line logic
+   * when possible because the loop overhead will limit our maximum transfer
+   * rate.
+   */
+
+  /* Exchange bit 7 with the slave */
+
+  datain = priv->exchange(priv, dataout & (1 << 7));
+
+  /* Exchange bit 6 with the slave */
+
+  datain <<= 1;
+  datain |= priv->exchange(priv, dataout & (1 << 6));
+
+  /* Exchange bit 5 with the slave */
+
+  datain <<= 1;
+  datain |= priv->exchange(priv, dataout & (1 << 5));
+
+  /* Exchange bit 4 with the slave */
+
+  datain <<= 1;
+  datain |= priv->exchange(priv, dataout & (1 << 4));
+
+  /* Exchange bit 3 with the slave */
+
+  datain <<= 1;
+  datain |= priv->exchange(priv, dataout & (1 << 3));
+
+  /* Exchange bit 2 with the slave */
+
+  datain <<= 1;
+  datain |= priv->exchange(priv, dataout & (1 << 2));
+
+  /* Exchange bit 1 with the slave */
+
+  datain <<= 1;
+  datain |= priv->exchange(priv, dataout & (1 << 1));
+
+  /* Exchange bit 0 with the slave */
+
+  datain <<= 1;
+  datain |= priv->exchange(priv, dataout & (1 << 0));
+
+  return datain;
+}
+#endif