Add simple touch calibrate and test sketch

This one does not need SPIFFS, cal data is embedded in sketch by user.

examples/Generic/Touch_calibrate/Touch_calibrate.ino

@@ -0,0 +1,103 @@
+/*
+  Sketch to generate the setup() calibration values, these are reported
+  to the Serial Monitor.
+
+  The sketch has been tested on the ESP8266 and screen with XPY2046 driver.
+*/
+
+#include <SPI.h>
+#include <TFT_eSPI.h>      // Hardware-specific library
+
+TFT_eSPI tft = TFT_eSPI(); // Invoke custom library
+
+//------------------------------------------------------------------------------------------
+
+void setup() {
+  // Use serial port
+  Serial.begin(115200);
+
+  // Initialise the TFT screen
+  tft.init();
+
+  // Set the rotation before we calibrate
+  tft.setRotation(1);
+
+  // Calibrate the touch screen and retrieve the scaling factors
+  touch_calibrate();
+
+/*
+  // Replace above line with the code sent to Serial Monitor
+  // once calibration is complete, e.g.:
+  uint16_t calData[5] = { 286, 3534, 283, 3600, 6 };
+  tft.setTouch(calData);
+*/
+
+  // Clear the screen
+  tft.fillScreen(TFT_BLACK);
+  tft.drawCentreString("Touch screen to test!",tft.width()/2, tft.height()/2, 2);
+}
+
+//------------------------------------------------------------------------------------------
+
+void loop(void) {
+  uint16_t x = 0, y = 0; // To store the touch coordinates
+
+  // Pressed will be set true is there is a valid touch on the screen
+  boolean pressed = tft.getTouch(&x, &y);
+
+  // Draw a shite spot at the detected coordinates
+  if (pressed) {
+    tft.fillCircle(x, y, 2, TFT_WHITE);
+    //Serial.print("x,y = ");
+    //Serial.print(x);
+    //Serial.print(",");
+    //Serial.println(y);
+  }
+}
+
+//------------------------------------------------------------------------------------------
+
+// Code to run a screen calibration, not needed when calibration values set in setup()
+void touch_calibrate()
+{
+  uint16_t calData[5];
+  uint8_t calDataOK = 0;
+
+  // Calibrate
+  tft.fillScreen(TFT_BLACK);
+  tft.setCursor(20, 0);
+  tft.setTextFont(2);
+  tft.setTextSize(1);
+  tft.setTextColor(TFT_WHITE, TFT_BLACK);
+
+  tft.println("Touch corners as indicated");
+
+  tft.setTextFont(1);
+  tft.println();
+
+  tft.calibrateTouch(calData, TFT_MAGENTA, TFT_BLACK, 15);
+
+  Serial.println(); Serial.println();
+  Serial.println("// Use this calibration code in setup():");
+  Serial.print("  uint16_t calData[5] = ");
+  Serial.print("{ ");
+
+  for (uint8_t i = 0; i < 5; i++)
+  {
+    Serial.print(calData[i]);
+    if (i < 4) Serial.print(", ");
+  }
+
+  Serial.println(" };");
+  Serial.print("  tft.setTouch(calData);");
+  Serial.println(); Serial.println();
+
+  tft.fillScreen(TFT_BLACK);
+  
+  tft.setTextColor(TFT_GREEN, TFT_BLACK);
+  tft.println("Calibration complete!");
+  tft.println("Calibration code sent to Serial port.");
+
+  delay(4000);
+}
+