LILYGO T-ETH-Lite-ESP32S3 and ST7796S Display - Whitescreen problem

[Queequack]

What I wanted to do:

The prerequisite is the use of a T-ETH-Lite with ESP32-S3. I am looking for a 3.5 inch display that runs as smoothly as possible. This discussion led me to the ST7796 display. I wanted to use it via 4 line SPI at 80 MHz. I also wanted to activate DMA, as described here for the ESP32-S3.

I connected the 40-pin FPC of the ordered ST7796 LCD with Capacitive Touch according to the Datasheet and the pins, especially for SPI communication, according to the ESP32-S3-Box Setup (see screenshots below). LilyGo provides the ESP32-S3-Box in the Platformio.ini for the T-ETH-Lite-ESP32S3. I don't use an SD card or Ethernet.

Problem:

To ensure that my code (see below) works, I have connected an RGB LED. This flashes as intended in the code. Otherwise, the code only intends to color the display red. To see a change, the display color should change with every LED action. The display simply remains white (Backlight switched on).

I use VSCode with PlatformIO and the Arduino Framework.

Code:

User_setup.h:

#define USER_SETUP_INFO "User_Setup"

#define ST7796_DRIVER

#define TFT_MISO  0
#define TFT_MOSI  6
#define TFT_SCLK  7
#define TFT_CS    5
#define TFT_DC    4
#define TFT_RST  15

#define LOAD_GLCD   // Font 1. Original Adafruit 8 pixel font needs ~1820 bytes in FLASH
#define LOAD_FONT2  // Font 2. Small 16 pixel high font, needs ~3534 bytes in FLASH, 96 characters
#define LOAD_FONT4  // Font 4. Medium 26 pixel high font, needs ~5848 bytes in FLASH, 96 characters
#define LOAD_FONT6  // Font 6. Large 48 pixel font, needs ~2666 bytes in FLASH, only characters 1234567890:-.apm
#define LOAD_FONT7  // Font 7. 7 segment 48 pixel font, needs ~2438 bytes in FLASH, only characters 1234567890:-.
#define LOAD_FONT8  // Font 8. Large 75 pixel font needs ~3256 bytes in FLASH, only characters 1234567890:-.
//#define LOAD_FONT8N // Font 8. Alternative to Font 8 above, slightly narrower, so 3 digits fit a 160 pixel TFT
#define LOAD_GFXFF  // FreeFonts. Include access to the 48 Adafruit_GFX free fonts FF1 to FF48 and custom fonts

#define SMOOTH_FONT

#define SPI_FREQUENCY  27000000

main.cpp:

#include <Arduino.h>
#include <TFT_eSPI.h>
#include <FastLED.h>

// ################## Display ##################
TFT_eSPI tft = TFT_eSPI();
// #############################################

// ############### Flashing LED ###############
CRGB rgbLed[1];
bool ledState = true;
unsigned long lastTime = 0;
unsigned long blinkTime = 500;
// #############################################

bool timerExpired(unsigned long, unsigned long);

void setup()
{
  // ################## Display ##################
  tft.init();
  tft.setRotation(1);
  tft.fillScreen(TFT_RED);
  //tft.fillScreen(TFT_BLACK);
  //tft.setCursor(0,0,4);
  //tft.setTextColor(TFT_WHITE);
  //tft.println ("Hello World!");
  // #############################################

  // ############### Flashing LED ###############
  FastLED.addLeds<SK6812, 38, GRB>(rgbLed, 1);
  FastLED.setBrightness(50);
  rgbLed[0] = CRGB::Black; FastLED.show();
  ledState = false;
  // #############################################
}

void loop() 
{
  // ############### Flashing LED ###############
  if (timerExpired(lastTime, blinkTime))
  {
    lastTime = millis();
    if(ledState) { rgbLed[0] = CRGB::Black; FastLED.show(); ledState = false; tft.fillScreen(TFT_RED);   }
    else         { rgbLed[0] = CRGB::Violet; FastLED.show(); ledState = true; tft.fillScreen(TFT_BLACK); }
  }
  // #############################################
}

/*********************************************************************************************\
 * Timer */
bool timerExpired(unsigned long last, unsigned long del)
{
  if (millis() - last >= del) return true;
  return false;
}

platformio.ini:

[platformio]
default_envs = T-ETH-Lite-ESP32S3

[env]
platform = [email protected]
framework = arduino
upload_speed =  921600
monitor_speed = 115200
;monitor_filters =
	;default
	;esp32_exception_decoder

;build_flags =
;	-DCORE_DEBUG_LEVEL=1

;Use OTA update firmware
; upload_protocol = espota
; upload_port = 192.168.36.107
    
; ESP32-S3-WROOM-1 + W5500 FLASH:16MB PSRAM:8MB OPI
[env:T-ETH-Lite-ESP32S3]
board=esp32s3box
build_flags = 
	${env.build_flags}
	-DBOARD_HAS_PSRAM
    -DLILYGO_TETH_POE
	-DLILYGO_T_ETH_LITE_ESP32S3
    -UARDUINO_USB_CDC_ON_BOOT
	-D USER_SETUP_LOADED=1
    -include $PROJECT_LIBDEPS_DIR/$PIOENV/TFT_eSPI/User_Setup.h

lib_ignore = 
    Ethernet

lib_deps =
    fastled/FastLED @ ^3.6.0
	;bodmer/TFT_eSPI @ ^2.5.43 ; Display Treiber
	TFT_eSPI

Pin assignment

Regards René

[Basitadam]

Hi,
Which lines are uncommented in your "User_Setup_Select.h" file?

[Queequack]

Hi,

#include <User_Setup.h>

User_Setup.h is included via platformio.ini:

build_flags = 
     ;...
     -include $PROJECT_LIBDEPS_DIR/$PIOENV/TFT_eSPI/User_Setup.h

I've also tested Setup251_ESP32_S3_Box.h with ST7796_DRIVER (instead of ILI9341_DRIVER).

Regards

[Basitadam]

What are you getting from the serial port?

1- Disconnect MISO line for now and modify to this "#define TFT_MISO -1" in the User_Setup.h
2- Add this to the User_Setup.h : #define USE_HSPI_PORT

Now what are you getting from the serial port?

BR,
Tim

[Queequack]

Hi Tim, thanks for your help!

I have found the solution. I was convinced that the RESET pin can be selected at will. Since IO48 is not led out via the pin header on the T-ETH-Lite, I selected IO15. Both work:

• I have set TFT_RST -1 and connected TFT_RST to RST of the ESP32-S3.
• Then I used TFT_RST 48 and held the jumper cable to the pin by hand.

I've disconnected MISO (defined -1), I won't need it anyhow. And #define USE_HSPI_PORT had no effect (even with the working solution with the RST pin).

I think the thread can be closed. May it help other lost souls.

Regards René

PS: If you have a tip on how I can run TFT_eSPI (later also with LVGL) and the rest of my program on the two seperate CPUs of the ESP32-S3, let me know.

[Basitadam]

I did a small test on dual core ( it is not recommended if you are using bluetooth and/or wifi):
`
#include <TFT_eSPI.h> // Library for drawing on the display
TFT_eSPI tft = TFT_eSPI(); // Invoke custom library
TFT_eSprite Needle = TFT_eSprite(&tft); // Sprite object for needle
TFT_eSprite Bgnd = TFT_eSprite(&tft); // Sprite object

// uncomment only one of the header files to choose between two color themes - VIOLET or RED
#include "Tekli.h" // images for boost gauge graphics
//#include "boost_gauge_images_VIOLET.h" // all 61 images for boost gauge graphics

#define BasilmayacakRenk TFT_BLACK

// set the mode
int mode = 1; // 0 = ping pong animation, 1 = get value from boost pressure sensor

int frame = 0; // current frame
int frame_inc = 1; // frame increment

uint16_t iks,ye,sayici;
uint8_t Core0Greet=1;

float psi_older[20]; // store a few older readings for smoother readout

TaskHandle_t Task1;
TaskHandle_t Task2;

void setup()
{
Serial.begin(115200);

tft.begin(); // initialize the display
//tft.setRotation(1); // rotation of the display set to landscape
tft.setRotation(1); // in this rotation, the USB port is on the "bottom" of the screen
tft.setSwapBytes(true); // Swap the colour byte order when rendering
tft.fillScreen(TFT_BLACK); // fill display with the black color

CrateBackGround();
CreateNeedle();
tft.setPivot(120, 120); // Adjust middle for the TFT pivot point

Bgnd.pushImage(0, 0, 240, 240, epd_bitmap_Taban); // draw the fullscreen boost gauge image
Needle.pushRotated(&Bgnd,iks,TFT_BLACK); // Plot rotated Sprite, black being transparent from original image
Bgnd.pushSprite(0,0);

pinMode(4, INPUT); // GPIO4 as analog input
analogReadResolution(12); //set the resolution of analog input to 12 bits (0-4096)

xTaskCreatePinnedToCore(
Core1code, /* Task function. /
"Core1", / name of task. /
20000, / Stack size of task /
NULL, / parameter of the task /
2, / priority of the task, high the number = more priority /
&Task1, / Task handle to keep track of created task /
1); / pin task to core 1 */
delay(500);

xTaskCreatePinnedToCore(
Core0code, /* Task function. /
"Core0", / name of task. /
10000, / Stack size of task /
NULL, / parameter of the task /
1, / priority of the task /
&Task2, / Task handle to keep track of created task /
0); / pin task to core 0 */
delay(500);
}

void Core1code( void * pvParameters )
{
Serial.print("Graphics is running on core ");
Serial.println(xPortGetCoreID());

while(Core0Greet); // wait for the core0 do its greeting

while(1)
{
sayici++;
if (mode == 0)
{ // 0 = ping pong animation

// play the animation - ping-pong - going from min to max and than back from max to min
frame = frame + frame_inc;
if ((frame > 60) && (frame_inc > 0)) {
  frame = 60;
  frame_inc = -1;
} else if ((frame < 0) && (frame_inc < 0)) {
  frame = 0;
  frame_inc = 1;
} 

}
else if (mode == 1)
{ // 1 = get value from boost pressure sensor

int pot_value = analogRead(4);                                    // read analog in value from the boost pressure sensor 0-4096 

float calculated_bar_pressure = (pot_value - 587.0) / 631.0;      // calculate BAR pressure based on the voltage, this calculation was done based on measuring analog gauge
float calculated_psi_pressure = calculated_bar_pressure * 14.504; // calculate PSI pressure from BAR pressure

// store a few older measurements
for (int i = 0; i < 9; i++) {
  psi_older[i] = psi_older[i+1];
}
psi_older[9] = calculated_psi_pressure;

float psi_combined = 0;
for (int i = 0; i < 10; i++) {
  psi_combined = psi_combined + psi_older[i];
}
psi_combined = psi_combined / 10; // final pressure value is the average of last 10 readings

// set the image to be displayed based on the PSI pressure,
// we have 60 images, and the PSI pressure should be in the range -15 .. 45, i.e., also 60 steps
int image_pressure = round(psi_combined) + 15;
image_pressure = constrain(image_pressure, 0, 60); // restrict the images to 0-60 in case the PSI pressure is outside the range of -15..45

  iks=185+(image_pressure*3);

  Bgnd.pushImage(0, 0, 240, 240, epd_bitmap_Taban);       // draw the fullscreen boost gauge image 
  Needle.pushRotated(&Bgnd,iks, TFT_BLACK);               // Plot rotated Sprite, black being transparent from original image
  Bgnd.pushSprite(0,0);

  delay(20);      // 24 fps delay. Let core0 do its tasks also
}

}
}

void Core0code( void * pvParameters )
{
Serial.print("Serial is running on core ");
Serial.println(xPortGetCoreID());
Serial.println("");

delay(10); // let core0 do its greeting
Core0Greet=0;

while(1)
{
Serial.println(sayici);
delay(700);
}
}

void loop()
{
NOP();
}

void CrateBackGround(void)
{
Bgnd.setSwapBytes(true);
Bgnd.setColorDepth(16);
Bgnd.createSprite(240,240); // create the needle Sprite
Bgnd.fillSprite(TFT_BLACK); // in init tft background already filled in black
Bgnd.pushImage(0, 0, 240, 240, epd_bitmap_Taban); // draw the fullscreen boost gauge image
Bgnd.pushSprite(0,0);
}

void CreateNeedle(void)
{
Needle.setSwapBytes(true);
Needle.setColorDepth(16);
Needle.createSprite(135,68); // create the needle Sprite
Needle.fillSprite(TFT_BLACK); // Color that will be NOT displayed from sprite
uint16_t piv_x = 41; // x pivot of Sprite
uint16_t piv_y = 34; // y pivot of Sprite (middle)
Needle.setPivot(piv_x, piv_y); // Set pivot point in this Sprite
Needle.pushImage(0,0,135,68,epd_bitmap_gauge_needle);
}

`

ESP32_S3_Zero_Sprite_RotatedNeedleDualCore.txt

Tekli.h is an image file. A 240x240 pixel bmp image transferred to RGB565

[Queequack]

Thank you very much, I will try it out soon.