4.0" TFT with ST7796S driver and TFT_eSPI library

[Guytou11]

Hi, I am using a 4.0" TFT with ST7796S driver connected to an ESP32 using the setup27from the TFT_eSPI library.
I verified the suggested connections which are all OK.
#define TFT_MISO 19
#define TFT_MOSI 23
#define TFT_SCLK 18
#define TFT_CS 15 // Chip select control pin
#define TFT_DC 2 // Data Command control pin
#define TFT_RST 4
However, the TFT display stays black, no action at all.
I am wondering if the display is a failed one.
Any suggestions how I can test this ?

[Guytou11]

further information : I used the below code example to test the display and I am using PlatformIO 👍 /*
The TFT_eSPI library incorporates an Adafruit_GFX compatible
button handling class, this sketch is based on the Arduin-o-phone
example.

This example displays a keypad where numbers can be entered and
sent to the Serial Monitor window.

The sketch has been tested on the ESP8266 (which supports SPIFFS)

The minimum screen size is 320 x 240 as that is the keypad size.

TOUCH_CS and SPI_TOUCH_FREQUENCY must be defined in the User_Setup.h file
for the touch functions to do anything.
*/

// The SPIFFS (FLASH filing system) is used to hold touch screen
// calibration data

#include "FS.h"

#include <SPI.h>
#include <TFT_eSPI.h> // Hardware-specific library

TFT_eSPI tft = TFT_eSPI(); // Invoke custom library

// This is the file name used to store the calibration data
// You can change this to create new calibration files.
// The SPIFFS file name must start with "/".
#define CALIBRATION_FILE "/TouchCalData2"

// Set REPEAT_CAL to true instead of false to run calibration
// again, otherwise it will only be done once.
// Repeat calibration if you change the screen rotation.
#define REPEAT_CAL false

// Keypad start position, key sizes and spacing
#define KEY_X 40 // Centre of key
#define KEY_Y 96
#define KEY_W 62 // Width and height
#define KEY_H 30
#define KEY_SPACING_X 18 // X and Y gap
#define KEY_SPACING_Y 20
#define KEY_TEXTSIZE 1 // Font size multiplier

// Using two fonts since numbers are nice when bold
#define LABEL1_FONT &FreeSansOblique12pt7b // Key label font 1
#define LABEL2_FONT &FreeSansBold12pt7b // Key label font 2

// Numeric display box size and location
#define DISP_X 1
#define DISP_Y 10
#define DISP_W 238
#define DISP_H 50
#define DISP_TSIZE 3
#define DISP_TCOLOR TFT_CYAN

// Number length, buffer for storing it and character index
#define NUM_LEN 12
char numberBuffer[NUM_LEN + 1] = "";
uint8_t numberIndex = 0;

// We have a status line for messages
#define STATUS_X 120 // Centred on this
#define STATUS_Y 65

// Create 15 keys for the keypad
char keyLabel[15][5] = {"New", "Del", "Send", "1", "2", "3", "4", "5", "6", "7", "8", "9", ".", "0", "#" };
uint16_t keyColor[15] = {TFT_RED, TFT_DARKGREY, TFT_DARKGREEN,
TFT_BLUE, TFT_BLUE, TFT_BLUE,
TFT_BLUE, TFT_BLUE, TFT_BLUE,
TFT_BLUE, TFT_BLUE, TFT_BLUE,
TFT_BLUE, TFT_BLUE, TFT_BLUE
};

// Invoke the TFT_eSPI button class and create all the button objects
TFT_eSPI_Button key[15];

//------------------------------------------------------------------------------------------

//------------------------------------------------------------------------------------------

void drawKeypad()
{
// Draw the keys
for (uint8_t row = 0; row < 5; row++) {
for (uint8_t col = 0; col < 3; col++) {
uint8_t b = col + row * 3;

  if (b < 3) tft.setFreeFont(LABEL1_FONT);
  else tft.setFreeFont(LABEL2_FONT);

  key[b].initButton(&tft, KEY_X + col * (KEY_W + KEY_SPACING_X),
                    KEY_Y + row * (KEY_H + KEY_SPACING_Y), // x, y, w, h, outline, fill, text
                    KEY_W, KEY_H, TFT_WHITE, keyColor[b], TFT_WHITE,
                    keyLabel[b], KEY_TEXTSIZE);
  key[b].drawButton();
}

}
}

//------------------------------------------------------------------------------------------

void touch_calibrate()
{
uint16_t calData[5];
uint8_t calDataOK = 0;

// check file system exists
if (!SPIFFS.begin()) {
Serial.println("formatting file system");
SPIFFS.format();
SPIFFS.begin();
}

// check if calibration file exists and size is correct
if (SPIFFS.exists(CALIBRATION_FILE)) {
if (REPEAT_CAL)
{
// Delete if we want to re-calibrate
SPIFFS.remove(CALIBRATION_FILE);
}
else
{
File f = SPIFFS.open(CALIBRATION_FILE, "r");
if (f) {
if (f.readBytes((char *)calData, 14) == 14)
calDataOK = 1;
f.close();
}
}
}

if (calDataOK && !REPEAT_CAL) {
// calibration data valid
tft.setTouch(calData);
} else {
// data not valid so recalibrate
tft.fillScreen(TFT_BLUE);
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();

if (REPEAT_CAL) {
  tft.setTextColor(TFT_RED, TFT_BLACK);
  tft.println("Set REPEAT_CAL to false to stop this running again!");
}

tft.calibrateTouch(calData, TFT_MAGENTA, TFT_BLACK, 15);

tft.setTextColor(TFT_GREEN, TFT_BLACK);
tft.println("Calibration complete!");

// store data
File f = SPIFFS.open(CALIBRATION_FILE, "w");
if (f) {
  f.write((const unsigned char *)calData, 14);
  f.close();
}

}
}

//------------------------------------------------------------------------------------------

// Print something in the mini status bar
void status(const char *msg) {
tft.setTextPadding(240);
//tft.setCursor(STATUS_X, STATUS_Y);
tft.setTextColor(TFT_WHITE, TFT_DARKGREY);
tft.setTextFont(0);
tft.setTextDatum(TC_DATUM);
tft.setTextSize(1);
tft.drawString(msg, STATUS_X, STATUS_Y);
}

//------------------------------------------------------------------------------------------

void setup() {
// Use serial port
Serial.begin(9600);

// 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();

// Clear the screen
tft.fillScreen(TFT_BLACK);

// Draw keypad background
tft.fillRect(0, 0, 240, 320, TFT_DARKGREY);

// Draw number display area and frame
tft.fillRect(DISP_X, DISP_Y, DISP_W, DISP_H, TFT_BLACK);
tft.drawRect(DISP_X, DISP_Y, DISP_W, DISP_H, TFT_WHITE);

// Draw keypad
drawKeypad();
}

//------------------------------------------------------------------------------------------

void loop(void) {
uint16_t t_x = 0, t_y = 0; // To store the touch coordinates

// Pressed will be set true is there is a valid touch on the screen
bool pressed = tft.getTouch(&t_x, &t_y);

// / Check if any key coordinate boxes contain the touch coordinates
for (uint8_t b = 0; b < 15; b++) {
if (pressed && key[b].contains(t_x, t_y)) {
key[b].press(true); // tell the button it is pressed
} else {
key[b].press(false); // tell the button it is NOT pressed
}
}

// Check if any key has changed state
for (uint8_t b = 0; b < 15; b++) {

if (b < 3) tft.setFreeFont(LABEL1_FONT);
else tft.setFreeFont(LABEL2_FONT);

if (key[b].justReleased()) key[b].drawButton();     // draw normal

if (key[b].justPressed()) {
  key[b].drawButton(true);  // draw invert

  // if a numberpad button, append the relevant # to the numberBuffer
  if (b >= 3) {
    if (numberIndex < NUM_LEN) {
      numberBuffer[numberIndex] = keyLabel[b][0];
      numberIndex++;
      numberBuffer[numberIndex] = 0; // zero terminate
    }
    status(""); // Clear the old status
  }

  // Del button, so delete last char
  if (b == 1) {
    numberBuffer[numberIndex] = 0;
    if (numberIndex > 0) {
      numberIndex--;
      numberBuffer[numberIndex] = 0;//' ';
    }
    status(""); // Clear the old status
  }

  if (b == 2) {
    status("Sent value to serial port");
    Serial.println(numberBuffer);
  }
  // we dont really check that the text field makes sense
  // just try to call
  if (b == 0) {
    status("Value cleared");
    numberIndex = 0; // Reset index to 0
    numberBuffer[numberIndex] = 0; // Place null in buffer
  }

  // Update the number display field
  tft.setTextDatum(TL_DATUM);        // Use top left corner as text coord datum
  tft.setFreeFont(&FreeSans18pt7b);  // Choose a nice font that fits box
  tft.setTextColor(DISP_TCOLOR);     // Set the font colour

  // Draw the string, the value returned is the width in pixels
  int xwidth = tft.drawString(numberBuffer, DISP_X + 4, DISP_Y + 12);

  // Now cover up the rest of the line up by drawing a black rectangle.  No flicker this way
  // but it will not work with italic or oblique fonts due to character overlap.
  tft.fillRect(DISP_X + 4 + xwidth, DISP_Y + 1, DISP_W - xwidth - 5, DISP_H - 2, TFT_BLACK);

  delay(10); // UI debouncing
}

}
}

[Guytou11]

In the meantime, I solved this issue.