XPT2046 LLD Major Update

Added 7 point median filtering to reduce noise
TOUCHPADDriver structure now encapsulates the IRQ pin, so removed
the TP_CS_ and TP_IRQ_ macros
Added generic tp_lld_read_value method to read any ADC channel from
the XPT2046, this includes on-chip temperature sensor and VBAT input
Improved SPI bus sharing, with the optional TOUCHPAD_SPI_PROLOGUE and
TOUCHPAD_SPI_EPILOGUE macros

1 files changed, 123 insertions, 32 deletions

diff --git a/drivers/touchpad/XPT2046/touchpad_lld.c b/drivers/touchpad/XPT2046/touchpad_lld.c
index 24afcab4..16e4db79 100644
--- a/drivers/touchpad/XPT2046/touchpad_lld.c
+++ b/drivers/touchpad/XPT2046/touchpad_lld.c
@@ -36,9 +36,6 @@
 /* Driver local definitions.                                                 */

 /*===========================================================================*/

 

-#define TP_CS_HIGH      palSetPad(TP_CS_PORT, TP_CS)

-#define TP_CS_LOW       palClearPad(TP_CS_PORT, TP_CS)

-

 #ifdef UNUSED

 #elif defined(__GNUC__)

 # define UNUSED(x) UNUSED_ ## x __attribute__((unused))

@@ -52,13 +49,15 @@
 /* Driver exported variables.                                                */

 /*===========================================================================*/

 

-#if !defined(__DOXYGEN__)

-	TOUCHPADDriver Touchpad;

-#endif

-

 /*===========================================================================*/

 /* Driver local variables.                                                   */

 /*===========================================================================*/

+#if !defined(__DOXYGEN__)

+    /* Local copy of the current touchpad driver */

+    static const TOUCHPADDriver *tpDriver;

+

+    static uint16_t sampleBuf[7];

+#endif

 

 /*===========================================================================*/

 /* Driver local functions.                                                   */

@@ -79,30 +78,104 @@
  *

  * @notapi

  */

-void tp_lld_init(TOUCHPADDriver *tp) {

-	spiStart(tp->spid, tp->spicfg);

+void tp_lld_init(const TOUCHPADDriver *tp) {

+  tpDriver=tp;

+

+  if (tpDriver->direct_init)

+    spiStart(tpDriver->spip, tpDriver->spicfg);

+}

+

+

+/**

+ * @brief   Reads a conversion from the touchpad

+ *

+ * @param[in] cmd    The command bits to send to the touchpad

+ *

+ * @return  The read value 12-bit right-justified

+ *

+ * @note    This function only reads data, it is assumed that the pins are

+ *          configured properly and the bus has been acquired beforehand

+ *

+ * @notapi

+ */

+uint16_t tp_lld_read_value(uint8_t cmd) {

+  static uint8_t txbuf[3]={0};

+  static uint8_t rxbuf[3]={0};

+  uint16_t ret;

+

+  txbuf[0]=cmd;

+

+  spiExchange(tpDriver->spip, 3, txbuf, rxbuf);

+

+  ret = (rxbuf[1] << 5) | (rxbuf[2] >> 3);

+

+  return ret;

+}

+

+/**

+ * @brief   7-point median filtering code for touchpad samples

+ *

+ * @note    This is an internally used routine only.

+ *

+ * @notapi

+ */

+static void tp_lld_filter(void) {

+  uint16_t temp;

+  int i,j;

+

+  for (i=0; i<4; i++) {

+    for (j=i; j<7; j++) {

+      if (sampleBuf[i] > sampleBuf[j]) {

+        /* Swap the values */

+        temp=sampleBuf[i];

+        sampleBuf[i]=sampleBuf[j];

+        sampleBuf[j]=temp;

+      }

+    }

+  }

+

 }

 

 /**

  * @brief   Reads out the X direction.

  *

+ * @note    The samples are median filtered for greater noise reduction

+ *

  * @notapi

  */

 uint16_t tp_lld_read_x(void) {

-    uint8_t txbuf[1];

-    uint8_t rxbuf[2];

-    uint16_t x;

+  int i;

+

+#if defined(SPI_USE_MUTUAL_EXCLUSION)

+  spiAcquireBus(tpDriver->spip);

+#endif

+

+  TOUCHPAD_SPI_PROLOGUE();

+  palClearPad(tpDriver->spicfg->ssport, tpDriver->spicfg->sspad);

+

+  /* Discard the first conversion - very noisy and keep the ADC on hereafter

+   * till we are done with the sampling. Note that PENIRQ is disabled.

+   */

+  tp_lld_read_value(0xD1);

+

+  for (i=0;i<7;i++) {

+    sampleBuf[i]=tp_lld_read_value(0xD1);

+  }

 

-    txbuf[0] = 0xd0;

-    TP_CS_LOW;

-    spiSend(&SPID1, 1, txbuf);

-    spiReceive(&SPID1, 2, rxbuf);

-    TP_CS_HIGH;

+  /* Switch on PENIRQ once again - perform a dummy read */

+  tp_lld_read_value(0xD0);

 

-    x = rxbuf[0] << 4;

-    x |= rxbuf[1] >> 4;

+  palSetPad(tpDriver->spicfg->ssport, tpDriver->spicfg->sspad);

+  TOUCHPAD_SPI_EPILOGUE();

 

-    return x;

+#if defined(SPI_USE_MUTUAL_EXCLUSION)

+  spiReleaseBus(tpDriver->spip);

+#endif

+

+  /* Find the median - use selection sort */

+  tp_lld_filter();

+

+  return sampleBuf[3];

 }

 

 /*

@@ -111,20 +184,38 @@ uint16_t tp_lld_read_x(void) {
  * @notapi

  */

 uint16_t tp_lld_read_y(void) {

-    uint8_t txbuf[1];

-    uint8_t rxbuf[2];

-    uint16_t y;

+  int i;

+

+#if defined(SPI_USE_MUTUAL_EXCLUSION)

+  spiAcquireBus(tpDriver->spip);

+#endif

+

+  TOUCHPAD_SPI_PROLOGUE();

+  palClearPad(tpDriver->spicfg->ssport, tpDriver->spicfg->sspad);

 

-    txbuf[0] = 0x90;

-    TP_CS_LOW;

-    spiSend(&SPID1, 1, txbuf);

-    spiReceive(&SPID1, 2, rxbuf);

-    TP_CS_HIGH;

+  /* Discard the first conversion - very noisy and keep the ADC on hereafter

+   * till we are done with the sampling. Note that PENIRQ is disabled.

+   */

+  tp_lld_read_value(0x91);

+

+  for (i=0;i<7;i++) {

+    sampleBuf[i]=tp_lld_read_value(0x91);

+  }

+

+  /* Switch on PENIRQ once again - perform a dummy read */

+  tp_lld_read_value(0x90);

+

+  palSetPad(tpDriver->spicfg->ssport, tpDriver->spicfg->sspad);

+  TOUCHPAD_SPI_EPILOGUE();

+

+#ifdef SPI_USE_MUTUAL_EXCLUSION

+  spiReleaseBus(tpDriver->spip);

+#endif

 

-    y = rxbuf[0] << 4;

-    y |= rxbuf[1] >> 4;

+  /* Find the median - use selection sort */

+  tp_lld_filter();

 

-    return y;

+  return sampleBuf[3];

 }

 

 /* ---- Optional Routines ---- */

@@ -137,7 +228,7 @@ uint16_t tp_lld_read_y(void) {
 	 * @notapi

 	 */

 	 uint8_t tp_lld_irq(void) {

-		return (!palReadPad(TP_IRQ_PORT, TP_IRQ));

+		return (!palReadPad(tpDriver->tpIRQPort, tpDriver->tpIRQPin));

 	}

 #endif