Inconsistent pressure readings on my Touchscreen

Other Hardware General Electronics
1

I recently started a project with an ILI9341 TFT LCD and an Esp32.
My problem is that the pressure readings of the display are all over the place.

I already searched online and found a post about me having to mesure the resistance between xPlus and xMinus.
After doing so (347 Ohms) 1/4 of the screen gives me valid readings and im not sure where the problem is.

I am just using the Esp32 and display so there aren't any other component interfering.
Do you have any idea on what the reason for that behavior could be?

Specs:
Controller: AzDelivery Esp32 NodeMCU CP2102
Display: ILI9341 TFT LCD Arduino Shield
IDE: Visual Studio - PlatformIO

Connections

#define LCD_RD 2
#define LCD_WR 4
#define LCD_RS 15
#define LCD_CS 33
#define LCD_RST 32
#define LCD_D0 12

#define LCD_D1 13
#define LCD_D2 26
#define LCD_D3 25
#define LCD_D4 17
#define LCD_D5 16
#define LCD_D6 27
#define LCD_D7 14

My Readings in the area that seems to work:
Z lands between like 30 and 260

My readings in the area that doesn't work:
Z lands between like -300 and -16400

2

Hi, @cohron
Welcome to the forum.

Can you please post your full code?
Can you please post a circuit diagram?

Thanks.. Tom.. :smiley: :+1: :coffee: :australia:

3

Here is my full code that im using

#include <Arduino.h>
#include <MCUFRIEND_kbv.h>
#include <TouchScreen.h>
#include <EEPROM.h>
#include <iostream>

#define LCD_RD  2
#define LCD_WR  4
#define LCD_RS 15
#define LCD_CS 33
#define LCD_RST 32

#define LCD_D0 12
#define LCD_D1 13
#define LCD_D2 26
#define LCD_D3 25
#define LCD_D4 17
#define LCD_D5 16
#define LCD_D6 27
#define LCD_D7 14

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

int XP=LCD_D6, XM=LCD_RS, YP=LCD_WR, YM=LCD_D7;
const int LEFT=-2500,RIGHT=600,TOP=687,BOT=-2200;

int mappedX, mappedY;

bool enableDebugLogging = true;

TouchScreen touchScreen = TouchScreen(XP, YP, XM, YM, 347);
TSPoint touchScreenPoint;
MCUFRIEND_kbv tft;


int cursorStart = 0;
String message = "Hallo wie gehts";

void initializeTFTScreen() {
  tft.reset();
  tft.begin(tft.readID());
  tft.setRotation(1);
}

void mapTouchScreenPoints() {
  touchScreenPoint = touchScreen.getPoint();
  mappedX = map(touchScreenPoint.x, LEFT, RIGHT, 0, tft.width());
  mappedY = map(touchScreenPoint.y, TOP, BOT, 0, tft.height());
}

void printStringOnDisplay(const String &string, int x, int y) {
  int16_t x1, y1;
  uint16_t w, h;

  tft.fillScreen(BLACK);

  tft.getTextBounds(string, x, y, &x1, &y1, &w, &h);

  cursorStart = x-w/2;
  tft.setCursor(cursorStart, y - h / 2);

  tft.print(string);
}

void calibrateTouchScreen() {
  mapTouchScreenPoints();
  Serial.println("-----------------------");
  Serial.println("X: " + String(touchScreenPoint.x));
  Serial.println("Y: " + String(touchScreenPoint.y));
  Serial.println("Z: " + String(touchScreenPoint.z));
  Serial.println("mapped X: " + String(mappedX));
  Serial.println("mapped Y: " + String(mappedY));
}

void debugLog(String logEntry) {
  if (enableDebugLogging) {
    Serial.println(logEntry);
  }
}

void debugLog(int logEntry) {
  debugLog(String(logEntry));
}

void testThing() {
  tft.setTextColor(WHITE,BLACK);
  int cursorY = tft.getCursorY();
  tft.setCursor(cursorStart,cursorY);
  tft.print(message);
  cursorStart--;
  delay(25);
}

void setup() {
  initializeTFTScreen();
  Serial.begin(115200);
/*
  tft.setTextWrap(false);

  tft.setTextSize(3);
  printStringOnDisplay(message,tft.width()/2,tft.height()/2);
*/
}

void loop() {
//  debugLog(cursorStart);
  calibrateTouchScreen();
}

Could you tell me why you need a ciruit diagram of this project?
You can see my connections in my initial post.

4

I hope this is enough of a schematic :smiley:

image
image1920×845 153 KB

5

Dumb question:
Where are your power/ground wires.

Isn't this a shield made for a 5volt Arduino, which the 3.3volt-logic ESP32 is not.
Leo..

6

the connections are as they should be :slight_smile:

7

So you're saying that the Fritzy drawing is not representing what it really is.
Yeah, we get that a lot here.
Leo..

8

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