Implement mpr121 touch sensor capability to GPIO Expanders (#192)

Co-authored-by: Andy Boff <gitdev@plek.me.uk>

components/services/gpio_exp.c

@@ -60,6 +60,10 @@ static const char TAG[] = "gpio expander";
 static void   IRAM_ATTR intr_isr_handler(void* arg);
 static gpio_exp_t* find_expander(gpio_exp_t *expander, int *gpio);
 
+static esp_err_t mpr121_init(gpio_exp_t* self);
+static uint32_t  mpr121_read(gpio_exp_t* self);
+static void      mpr121_write(gpio_exp_t* self);
+
 static void 	pca9535_set_direction(gpio_exp_t* self);
 static uint32_t pca9535_read(gpio_exp_t* self);
 static void 	pca9535_write(gpio_exp_t* self);
@@ -98,6 +102,11 @@ static const struct gpio_exp_model_s {
 	void      (*set_direction)(gpio_exp_t* self);
 	void      (*set_pull_mode)(gpio_exp_t* self);
 } registered[] = {
+	{ .model = "mpr121",
+	  .trigger = GPIO_INTR_LOW_LEVEL,
+	  .init = mpr121_init,
+	  .read = mpr121_read,
+	  .write = mpr121_write, },	
 	{ .model = "pca9535",
 	  .trigger = GPIO_INTR_LOW_LEVEL,
 	  .set_direction = pca9535_set_direction,
@@ -498,6 +507,111 @@ static gpio_exp_t* find_expander(gpio_exp_t *expander, int *gpio) {
                                         DRIVERS                                       
 ****************************************************************************************/
 
+/****************************************************************************************
+ * MPR121 family : init, direction, read and write
+ */
+static esp_err_t mpr121_init(gpio_exp_t* self) {
+	// soft reset the MPR121
+	esp_err_t err = i2c_write(self->phy.port, self->phy.addr, 0x80, 0x63, 1);
+
+	/*
+	  There is variance of default values between libraries:
+                  Reg     AN3944     Adafruit_MPR121  BareConductive/MPR121
+	      MHDR    0x2b    0x01       0x01             0x01
+	      NHDR    0x2c    0x01       0x01             0x01
+	      NCLR    0x2d    0x00       0x0e             0x10
+	      FDLR    0x2e    0x00       0x00             0x20
+
+	      MHDF    0x2f    0x01       0x01             0x01
+	      NHDF    0x30    0x01       0x05             0x01
+	      NCLF    0x31    0xff       0x01             0x10
+	      FDLF    0x32    0x20       0x00             0x20
+
+	      NHDT    0x33    ----       0x00             0x01
+	      NCLT    0x34    ----       0x00             0x10
+	      FDLT    0x35    ----       0x00             0xff
+
+	      DTR     0x5b    ----       0x00             0x11
+	      AFE1    0x5c    ----       0x10             0xff
+	      AFE2    0x5d    0x04       0x20             0x30
+	      ECR     0x5e    0x0c       ----             0xcc
+
+	      ACCR0   0x7b    0x0b       0x0b             0x00
+	      ACCR1   0x7c    ----       ----             0x00
+	      USL     0x7d    0x9c       0xc8             0x00
+	      LSL     0x7e    0x65       0xb4             0x00
+	      TL      0x7f    0x8c       0x82             0x00
+
+	  BareConductive MPR121 values used below.
+	*/
+
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x2b, 0x01, 1); // MHDR
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x2c, 0x01, 1); // NHDR
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x2d, 0x10, 1); // NCLR
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x2e, 0x20, 1); // FDLR
+
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x2f, 0x01, 1); // MHDF
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x30, 0x01, 1); // NHDF
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x31, 0x10, 1); // NCLF
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x32, 0x20, 1); // FDLF
+
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x33, 0x01, 1); // NHDT
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x34, 0x10, 1); // NCLT
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x35, 0xff, 1); // FDLT
+
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x5b, 0x11, 1); // DTR
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x5c, 0xff, 1); // AFE1
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x5d, 0x30, 1); // AFE2
+	                                                                 // ECR set last
+
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x7b, 0x00, 1); // ACCR0
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x7c, 0x00, 1); // ACCR1
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x7d, 0x00, 1); // USL
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x7e, 0x00, 1); // LSL
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x7f, 0x00, 1); // TL
+
+
+	// Touch & Release thresholds
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x41, 0x28, 1); // ELE0 Touch Threshold
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x42, 0x14, 1); // ELE0 Release Threshold
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x43, 0x28, 1); // ELE1 Touch Threshold
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x44, 0x14, 1); // ELE1 Release Threshold
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x45, 0x28, 1); // ELE2 Touch Threshold
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x46, 0x14, 1); // ELE2 Release Threshold
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x47, 0x28, 1); // ELE3 Touch Threshold
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x48, 0x14, 1); // ELE3 Release Threshold
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x49, 0x28, 1); // ELE4 Touch Threshold
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x4a, 0x14, 1); // ELE4 Release Threshold
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x4b, 0x28, 1); // ELE5 Touch Threshold
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x4c, 0x14, 1); // ELE5 Release Threshold
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x4d, 0x28, 1); // ELE6 Touch Threshold
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x4e, 0x14, 1); // ELE6 Release Threshold
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x4f, 0x28, 1); // ELE7 Touch Threshold
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x50, 0x14, 1); // ELE7 Release Threshold
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x51, 0x28, 1); // ELE8 Touch Threshold
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x52, 0x14, 1); // ELE8 Release Threshold
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x53, 0x28, 1); // ELE9 Touch Threshold
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x54, 0x14, 1); // ELE9 Release Threshold
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x55, 0x28, 1); // ELE10 Touch Threshold
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x56, 0x14, 1); // ELE10 Release Threshold
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x57, 0x28, 1); // ELE11 Touch Threshold
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x58, 0x14, 1); // ELE11 Release Threshold
+
+	// finally set to run mode with 12 electrodes enabled
+	err |= i2c_write(self->phy.port, self->phy.addr, 0x5e, 0xcc, 1); // ECR
+
+	return err;
+}
+
+static uint32_t mpr121_read(gpio_exp_t* self) {
+	// only return the lower 12 bits of the pin status registers
+	return i2c_read(self->phy.port, self->phy.addr, 0x00, 2) & 0x0fff;
+}
+
+static void mpr121_write(gpio_exp_t* self) {
+	ESP_LOGE(TAG, "MPR121 GPIO write not implemented");
+}
+
 /****************************************************************************************
  * PCA9535 family : direction, read and write
  */