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

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) {
+void tp_lld_init(const TOUCHPADDriver *tp) {
-	spiStart(tp->spid, tp->spicfg);
+  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];
+  int i;
-    uint8_t rxbuf[2];
-    uint16_t x;
 
-    txbuf[0] = 0xd0;
+#if defined(SPI_USE_MUTUAL_EXCLUSION)
-    TP_CS_LOW;
+  spiAcquireBus(tpDriver->spip);
-    spiSend(&SPID1, 1, txbuf);
+#endif
-    spiReceive(&SPID1, 2, rxbuf);
-    TP_CS_HIGH;
 
-    x = rxbuf[0] << 4;
+  TOUCHPAD_SPI_PROLOGUE();
-    x |= rxbuf[1] >> 4;
+  palClearPad(tpDriver->spicfg->ssport, tpDriver->spicfg->sspad);
 
-    return x;
+  /* 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);
+  }
+
+  /* Switch on PENIRQ once again - perform a dummy read */
+  tp_lld_read_value(0xD0);
+
+  palSetPad(tpDriver->spicfg->ssport, tpDriver->spicfg->sspad);
+  TOUCHPAD_SPI_EPILOGUE();
+
+#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];
+  int i;
-    uint8_t rxbuf[2];
-    uint16_t y;
 
-    txbuf[0] = 0x90;
+#if defined(SPI_USE_MUTUAL_EXCLUSION)
-    TP_CS_LOW;
+  spiAcquireBus(tpDriver->spip);
-    spiSend(&SPID1, 1, txbuf);
+#endif
-    spiReceive(&SPID1, 2, rxbuf);
-    TP_CS_HIGH;
 
-    y = rxbuf[0] << 4;
+  TOUCHPAD_SPI_PROLOGUE();
-    y |= rxbuf[1] >> 4;
+  palClearPad(tpDriver->spicfg->ssport, tpDriver->spicfg->sspad);
 
-    return y;
+  /* 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
+
+  /* Find the median - use selection sort */
+  tp_lld_filter();
+
+  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
 

include/touchpad_lld.h

@@ -49,41 +49,76 @@
 	#define TOUCHPAD_HAS_PRESSURE	FALSE
 #endif
 
+#ifndef TOUCHPAD_SPI_PROLOGUE
+    #define TOUCHPAD_SPI_PROLOGUE()
+#endif
+
+#ifndef TOUCHPAD_SPI_EPILOGUE
+    #define TOUCHPAD_SPI_EPILOGUE()
+#endif
+
 /*===========================================================================*/
 /* Driver types.                                                             */
 /*===========================================================================*/
 
-typedef struct TOUCHPADDriver TOUCHPADDriver;
+typedef struct _TOUCHPADDriver TOUCHPADDriver;
 
 /**
  * @brief	Structure representing a Touchpad driver.
  */
-struct TOUCHPADDriver {
+struct _TOUCHPADDriver {
     /*
      * @brief   Pointer to SPI driver.
+     * @note    SPI driver must be enabled in mcuconf.h and halconf.h
      */
-	SPIDriver *spid;
+    SPIDriver       *spip;
 
     /*
-	 * @brief	SPI configuration.
+     * @brief   Pointer to the SPI configuration structure.
+     * @note    The lowest possible speed ~ 1-2MHz is to be used, otherwise
+     *          will result in a lot of noise
      */
-	SPIConfig *spicfg;	
+    const SPIConfig  *spicfg;
+
+    /*
+     * @brief   Touchscreen controller TPIRQ pin GPIO port
+     */
+    ioportid_t      tpIRQPort;
+
+    /*
+     * @brief   Touchscreen controller TPIRQ GPIO pin
+     * @note    The interface is polled as of now, interrupt support is
+     *          to be implemented in the future.
+     */
+    ioportmask_t    tpIRQPin;
+
+    /*
+     * @brief   Initialize the SPI with the configuration struct given or not
+     *          If TRUE, spiStart is called by the init, otherwise not
+     * @note    This is provided in such a case when SPI port is being shared
+     *          across multiple peripherals, so not to disturb the SPI bus.
+     *          You can use TOUCHPAD_SPI_PROLOGUE() and TOUCHPAD_SPI_EPILOGUE()
+     *          macros to change the SPI configuration or speed before and
+     *          after using the touchpad. An example case would be sharing the
+     *          bus with a fast flash memory chip.
+     */
+    bool_t          direct_init;
 };
 
+
 /*===========================================================================*/
 /* External declarations.                                                    */
 /*===========================================================================*/
 
-#if !defined(__DOXYGEN__)
-    extern TOUCHPADDriver Touchpad;
-#endif
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
 	/* Core functions */
-	void tp_lld_init(TOUCHPADDriver *tp);
+	void tp_lld_init(const TOUCHPADDriver *tp);
+
+	uint16_t tp_lld_read_value(uint8_t cmd);
 	uint16_t tp_lld_read_x(void);
 	uint16_t tp_lld_read_y(void);