Merge pull request #9 from liebman/use_z_test_for_press

XPT2046 optionally (Kconfig option) validate a touch with pressure, not just IRQ low

lvgl_touch/Kconfig

@@ -99,7 +99,6 @@ menu "LVGL Touch controller"
 	    range 0 39	
             default 35 if LV_PREDEFINED_PINS_38V1
             default 19
-
             help
             Configure the touchpanel MISO pin here.
 
@@ -109,7 +108,6 @@ menu "LVGL Touch controller"
 	    range 0 39	
             default 32 if LV_PREDEFINED_PINS_38V1
             default 23
-
             help
             Configure the touchpanel MOSI pin here.
 
@@ -135,7 +133,7 @@ menu "LVGL Touch controller"
             default 27 if LV_PREDEFINED_PINS_38V4
             default 25
             help
-            Configure the touchpanel CS pin here.
+            Configure the touchpanel IRQ pin here.
     endmenu
     
     menu "Touchpanel Configuration (XPT2046)"
@@ -180,6 +178,19 @@ menu "LVGL Touch controller"
             prompt "Invert Y coordinate value."
             default y
 
+        choice
+            prompt "Select touch detection method."
+            default LV_TOUCH_DETECT_IRQ
+            help
+                Select the controller for your touch panel.
+
+            config LV_TOUCH_DETECT_IRQ
+                bool "IRQ pin only"
+            config LV_TOUCH_DETECT_IRQ_PRESSURE
+                bool "IRQ pin and pressure"
+            config LV_TOUCH_DETECT_PRESSURE
+                bool "Pressure only"
+        endchoice
     endmenu
 
     menu "Touchpanel (FT6X06) Pin Assignments"

lvgl_touch/xpt2046.c

@@ -18,18 +18,26 @@
  *********************/
 #define TAG "XPT2046"
 
-#define CMD_X_READ  0b10010000
+#define CMD_X_READ  0b10010000  // NOTE: XPT2046 data sheet says this is actually Y
-#define CMD_Y_READ  0b11010000
+#define CMD_Y_READ  0b11010000  // NOTE: XPT2046 data sheet says this is actually X
+#define CMD_Z1_READ 0b10110000
+#define CMD_Z2_READ 0b11000000
 
 /**********************
  *      TYPEDEFS
  **********************/
+typedef enum {
+    TOUCH_NOT_DETECTED = 0,
+    TOUCH_DETECTED = 1,
+} xpt2046_touch_detect_t;
 
 /**********************
  *  STATIC PROTOTYPES
  **********************/
 static void xpt2046_corr(int16_t * x, int16_t * y);
 static void xpt2046_avg(int16_t * x, int16_t * y);
+static int16_t xpt2046_cmd(uint8_t cmd);
+static xpt2046_touch_detect_t xpt2048_is_touch_detected();
 
 /**********************
  *  STATIC VARIABLES
@@ -51,6 +59,9 @@ uint8_t avg_last;
  */
 void xpt2046_init(void)
 {
+    ESP_LOGI(TAG, "XPT2046 Initialization");
+
+#if XPT2046_TOUCH_IRQ || XPT2046_TOUCH_IRQ_PRESS
     gpio_config_t irq_config = {
         .pin_bit_mask = BIT64(XPT2046_IRQ),
         .mode = GPIO_MODE_INPUT,
@@ -59,10 +70,9 @@ void xpt2046_init(void)
         .intr_type = GPIO_INTR_DISABLE,
     };
     
-    ESP_LOGI(TAG, "XPT2046 Initialization");
-
     esp_err_t ret = gpio_config(&irq_config);
     assert(ret == ESP_OK);
+#endif
 }
 
 /**
@@ -74,21 +84,16 @@ bool xpt2046_read(lv_indev_drv_t * drv, lv_indev_data_t * data)
 {
     static int16_t last_x = 0;
     static int16_t last_y = 0;
-    bool valid = true;
+    bool valid = false;
 
-    int16_t x = 0;
+    int16_t x = last_x;
-    int16_t y = 0;
+    int16_t y = last_y;
+    if (xpt2048_is_touch_detected() == TOUCH_DETECTED)
+    {
+        valid = true;
 
-    uint8_t irq = gpio_get_level(XPT2046_IRQ);
+        x = xpt2046_cmd(CMD_X_READ);
-
+        y = xpt2046_cmd(CMD_Y_READ);
-    if (irq == 0) {
-		uint8_t data[2];
-		
-		tp_spi_read_reg(CMD_X_READ, data, 2);
-		x = (data[0] << 8) | data[1];
-		
-		tp_spi_read_reg(CMD_Y_READ, data, 2);
-		y = (data[0] << 8) | data[1];
         ESP_LOGI(TAG, "P(%d,%d)", x, y);
 
         /*Normalize Data back to 12-bits*/
@@ -102,11 +107,10 @@ bool xpt2046_read(lv_indev_drv_t * drv, lv_indev_data_t * data)
         last_y = y;
 
         ESP_LOGI(TAG, "x = %d, y = %d", x, y);
-    } else {
+    }
-        x = last_x;
+    else
-        y = last_y;
+    {
         avg_last = 0;
-        valid = false;
     }
 
     data->point.x = x;
@@ -119,6 +123,42 @@ bool xpt2046_read(lv_indev_drv_t * drv, lv_indev_data_t * data)
 /**********************
  *   STATIC FUNCTIONS
  **********************/
+static xpt2046_touch_detect_t xpt2048_is_touch_detected()
+{
+    // check IRQ pin if we IRQ or IRQ and preessure
+#if XPT2046_TOUCH_IRQ ||  XPT2046_TOUCH_IRQ_PRESS
+    uint8_t irq = gpio_get_level(XPT2046_IRQ);
+
+    if (irq != 0) {
+        return TOUCH_NOT_DETECTED;
+    }
+#endif
+    // check pressure if we are pressure or IRQ and pressure
+#if  XPT2046_TOUCH_PRESS || XPT2046_TOUCH_IRQ_PRESS
+    int16_t z1 = xpt2046_cmd(CMD_Z1_READ) >> 3;
+    int16_t z2 = xpt2046_cmd(CMD_Z2_READ) >> 3;
+
+    // this is not what the confusing datasheet says but it seems to
+    // be enough to detect real touches on the panel
+    int16_t z = z1 + 4096 - z2;
+
+    if (z < XPT2046_TOUCH_THRESHOLD)
+    {
+        return TOUCH_NOT_DETECTED;
+    }
+#endif
+
+    return TOUCH_DETECTED;
+}
+
+static int16_t xpt2046_cmd(uint8_t cmd)
+{
+    uint8_t data[2];
+    tp_spi_read_reg(cmd, data, 2);
+    int16_t val = (data[0] << 8) | data[1];
+    return val;
+}
+
 static void xpt2046_corr(int16_t * x, int16_t * y)
 {
 #if XPT2046_XY_SWAP != 0

lvgl_touch/xpt2046.h

@@ -35,6 +35,10 @@ extern "C" {
 #define XPT2046_X_INV           CONFIG_LV_TOUCH_INVERT_X
 #define XPT2046_Y_INV           CONFIG_LV_TOUCH_INVERT_Y
 #define XPT2046_XY_SWAP		    CONFIG_LV_TOUCH_XY_SWAP
+#define XPT2046_TOUCH_THRESHOLD 400 // Threshold for touch detection
+#define XPT2046_TOUCH_IRQ       CONFIG_LV_TOUCH_DETECT_IRQ
+#define XPT2046_TOUCH_IRQ_PRESS CONFIG_LV_TOUCH_DETECT_IRQ_PRESSURE
+#define XPT2046_TOUCH_PRESS     CONFIG_LV_TOUCH_DETECT_PRESSURE
 
 /**********************
  *      TYPEDEFS