Part 3 : Detecting Touch in TFT LCD Display using Library

In this tutorial, we will be learning how to detect touch in a TFT LCD Display.

The code to detect touch is quite simple as shown below :

#include <SPFD5408_Adafruit_GFX.h>    // Core graphics library
#include <SPFD5408_Adafruit_TFTLCD.h> // Hardware-specific library
#include <SPFD5408_TouchScreen.h>

#define LCD_CS A3 // Chip Select goes to Analog 3
#define LCD_CD A2 // Command/Data goes to Analog 2
#define LCD_WR A1 // LCD Write goes to Analog 1
#define LCD_RD A0 // LCD Read goes to Analog 0
#define LCD_RESET A4 // Can alternately just connect to Arduino's reset pin

#define BLACK   0x0000
#define BLUE    0x001F
#define RED     0xF800
#define GREEN   0x07E0
#define CYAN    0x07FF
#define MAGENTA 0xF81F
#define YELLOW  0xFFE0
#define WHITE   0xFFFF

//These are the pins for the shield!
#define YP A1
#define XM A2
#define YM 7
#define XP 6

Adafruit_TFTLCD tft(LCD_CS, LCD_CD, LCD_WR, LCD_RD, LCD_RESET);

//Adjust the sensitivity of the touchscreen to get desired output
#define sensitivity 1000
TouchScreen ts = TouchScreen(XP, YP, XM, YM, sensitivity);

// Calibrates value
#define MINPRESSURE 10
#define MAXPRESSURE 2000

void setup(void) {
  Serial.begin(9600);
  
  tft.reset();
  tft.begin(0x9341);
  tft.setRotation(3);
  tft.fillScreen(WHITE);
}

void loop() {
  TSPoint pinitial;
  pinMode(XM, OUTPUT); //Pin Config for TouchScreen
  pinMode(YP, INPUT);  //Pin Config for TouchScreen
  pinitial = ts.getPoint();
  
  pinMode(XM, OUTPUT); //Pin Config for LCD Display
  pinMode(YP, OUTPUT); //Pin Config for LCD Display 
  while (pinitial.z > MINPRESSURE && pinitial.z < MAXPRESSURE) {
    tft.fillRect(20,20,280,200,GREEN);
    delay(500);
    Serial.print("pinitial.x : ");
    Serial.println(pinitial.x);
    tft.fillRect(20,20,280,200,RED);
    break;
  }
}

The below PIN configurations are necessary when detecting touch

  pinMode(XM, OUTPUT); //Pin Config for TouchScreen
  pinMode(YP, INPUT);  //Pin Config for TouchScreen
  pinitial = ts.getPoint();

In contrast, when we are changing the graphical output in the TFT Display, we need to set pin configuration as shown below :

  pinMode(XM, OUTPUT); //Pin Config for LCD Display
  pinMode(YP, OUTPUT); //Pin Config for LCD Display 

However, it is important to understand that the above pins arrangement are subjected to experimentation. Different LCD Displays purchased from different supplier and companies may behave in a different and hence please try out a few pins configuration of OUTPUT and INPUT to get the desired result.

For more detailed instructions, please check my YouTube video below :