add Kconfig option for touch check

lvgl_touch/Kconfig

@@ -180,6 +180,10 @@ menu "LVGL Touch controller"
             prompt "Invert Y coordinate value."
             default y
 
+        config LV_TOUCH_CHECK
+            bool
+            prompt "Check touch pressure to validate LV_TOUCH_PIN_IRQ"
+            default n
     endmenu
 
     menu "Touchpanel (FT6X06) Pin Assignments"

lvgl_touch/xpt2046.c

@@ -33,6 +33,7 @@
  **********************/
 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 VARIABLES
@@ -68,14 +69,6 @@ void xpt2046_init(void)
     assert(ret == ESP_OK);
 }
 
-static int16_t readVal(uint8_t cmd)
-{
-    uint8_t data[2];
-    tp_spi_read_reg(cmd, data, 2);
-    int16_t val = (data[0] << 8) | data[1];
-    return val;
-}
-
 /**
  * Get the current position and state of the touchpad
  * @param data store the read data here
@@ -85,29 +78,32 @@ 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;
-    int16_t z = 0;
 
     uint8_t irq = gpio_get_level(XPT2046_IRQ);
 
-    // only compute Z if we think its pressed (irq)
+    if (irq == 0) {
-    if (irq == 0)
+#if XPT2046_TOUCH_CHECK != 0
+        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;
+
+        // seems the irq can be noisy so we only accept this as a touch if
+        // there is some pressure (z) detected
+        if (z >= Z_MIN)
         {
-        int16_t z1 = readVal(CMD_Z1_READ) >> 3;
+#endif
-        int16_t z2 = readVal(CMD_Z2_READ) >> 3;
+            valid = true;
 
-        z = z1 + 4096;
+            x = xpt2046_cmd(CMD_X_READ);
-        z -= z2;
+            y = xpt2046_cmd(CMD_Y_READ);
-    }
+            ESP_LOGI(TAG, "P(%d,%d)", x, y);
-
-    if (irq == 0 && z >= Z_MIN) {
-
-		x = readVal(CMD_X_READ);
-        y = readVal(CMD_Y_READ);
-		ESP_LOGI(TAG, "P(%d,%d,%d)", x, y, z);
 
             /*Normalize Data back to 12-bits*/
             x = x >> 4;
@@ -120,11 +116,14 @@ 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 {
+#if XPT2046_TOUCH_CHECK != 0
-        x = last_x;
+        }
-        y = last_y;
+#endif
+    }
+
+    if (!valid)
+    {
         avg_last = 0;
-        valid = false;
     }
 
     data->point.x = x;
@@ -137,6 +136,14 @@ bool xpt2046_read(lv_indev_drv_t * drv, lv_indev_data_t * data)
 /**********************
  *   STATIC FUNCTIONS
  **********************/
+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

@@ -35,7 +35,7 @@ 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_CHECK CONFIG_LV_TOUCH_CHECK
 /**********************
  *      TYPEDEFS
  **********************/