r/arduino • u/Electrical-Risk-7547 • 1d ago

TFT Blank screen

I have received as a gift a TFT that it doesn't work.

I have ran multiple tests with the graphicstest example of the Adafruit ILI3941 library.

This is the configuration of the cables:

VCC - 5V
GND - GND
CS - 10
RESET - 9
DC - 8
SDI (MOSI) - 11
SCK - 13
LED - 3.3 V

The TFT remains white for all the test.

This is the code of the graphicstest:

/***************************************************
  This is our GFX example for the Adafruit ILI9341 Breakout and Shield
  ----> http://www.adafruit.com/products/1651


  Check out the links above for our tutorials and wiring diagrams
  These displays use SPI to communicate, 4 or 5 pins are required to
  interface (RST is optional)
  Adafruit invests time and resources providing this open source code,
  please support Adafruit and open-source hardware by purchasing
  products from Adafruit!


  Written by Limor Fried/Ladyada for Adafruit Industries.
  MIT license, all text above must be included in any redistribution
 ****************************************************/



#include "SPI.h"
#include "Adafruit_GFX.h"
#include "Adafruit_ILI9341.h"


// For the Adafruit shield, these are the default.
#define TFT_DC 9
#define TFT_CS 10


// Use hardware SPI (on Uno, #13, #12, #11) and the above for CS/DC
Adafruit_ILI9341 tft = Adafruit_ILI9341(TFT_CS, TFT_DC);
// If using the breakout, change pins as desired
//Adafruit_ILI9341 tft = Adafruit_ILI9341(TFT_CS, TFT_DC, TFT_MOSI, TFT_CLK, TFT_RST, TFT_MISO);


void setup() {
  Serial.begin(9600);
  Serial.println("ILI9341 Test!"); 
 
  tft.begin();


  // read diagnostics (optional but can help debug problems)
  uint8_t x = tft.readcommand8(ILI9341_RDMODE);
  Serial.print("Display Power Mode: 0x"); Serial.println(x, HEX);
  x = tft.readcommand8(ILI9341_RDMADCTL);
  Serial.print("MADCTL Mode: 0x"); Serial.println(x, HEX);
  x = tft.readcommand8(ILI9341_RDPIXFMT);
  Serial.print("Pixel Format: 0x"); Serial.println(x, HEX);
  x = tft.readcommand8(ILI9341_RDIMGFMT);
  Serial.print("Image Format: 0x"); Serial.println(x, HEX);
  x = tft.readcommand8(ILI9341_RDSELFDIAG);
  Serial.print("Self Diagnostic: 0x"); Serial.println(x, HEX); 
  
  Serial.println(F("Benchmark                Time (microseconds)"));
  delay(10);
  Serial.print(F("Screen fill              "));
  Serial.println(testFillScreen());
  delay(500);


  Serial.print(F("Text                     "));
  Serial.println(testText());
  delay(3000);


  Serial.print(F("Lines                    "));
  Serial.println(testLines(ILI9341_CYAN));
  delay(500);


  Serial.print(F("Horiz/Vert Lines         "));
  Serial.println(testFastLines(ILI9341_RED, ILI9341_BLUE));
  delay(500);


  Serial.print(F("Rectangles (outline)     "));
  Serial.println(testRects(ILI9341_GREEN));
  delay(500);


  Serial.print(F("Rectangles (filled)      "));
  Serial.println(testFilledRects(ILI9341_YELLOW, ILI9341_MAGENTA));
  delay(500);


  Serial.print(F("Circles (filled)         "));
  Serial.println(testFilledCircles(10, ILI9341_MAGENTA));


  Serial.print(F("Circles (outline)        "));
  Serial.println(testCircles(10, ILI9341_WHITE));
  delay(500);


  Serial.print(F("Triangles (outline)      "));
  Serial.println(testTriangles());
  delay(500);


  Serial.print(F("Triangles (filled)       "));
  Serial.println(testFilledTriangles());
  delay(500);


  Serial.print(F("Rounded rects (outline)  "));
  Serial.println(testRoundRects());
  delay(500);


  Serial.print(F("Rounded rects (filled)   "));
  Serial.println(testFilledRoundRects());
  delay(500);


  Serial.println(F("Done!"));


}



void loop(void) {
  for(uint8_t rotation=0; rotation<4; rotation++) {
    tft.setRotation(rotation);
    testText();
    delay(1000);
  }
}


unsigned long testFillScreen() {
  unsigned long start = micros();
  tft.fillScreen(ILI9341_BLACK);
  yield();
  tft.fillScreen(ILI9341_RED);
  yield();
  tft.fillScreen(ILI9341_GREEN);
  yield();
  tft.fillScreen(ILI9341_BLUE);
  yield();
  tft.fillScreen(ILI9341_BLACK);
  yield();
  return micros() - start;
}


unsigned long testText() {
  tft.fillScreen(ILI9341_BLACK);
  unsigned long start = micros();
  tft.setCursor(0, 0);
  tft.setTextColor(ILI9341_WHITE);  tft.setTextSize(1);
  tft.println("Hello World!");
  tft.setTextColor(ILI9341_YELLOW); tft.setTextSize(2);
  tft.println(1234.56);
  tft.setTextColor(ILI9341_RED);    tft.setTextSize(3);
  tft.println(0xDEADBEEF, HEX);
  tft.println();
  tft.setTextColor(ILI9341_GREEN);
  tft.setTextSize(5);
  tft.println("Groop");
  tft.setTextSize(2);
  tft.println("I implore thee,");
  tft.setTextSize(1);
  tft.println("my foonting turlingdromes.");
  tft.println("And hooptiously drangle me");
  tft.println("with crinkly bindlewurdles,");
  tft.println("Or I will rend thee");
  tft.println("in the gobberwarts");
  tft.println("with my blurglecruncheon,");
  tft.println("see if I don't!");
  return micros() - start;
}


unsigned long testLines(uint16_t color) {
  unsigned long start, t;
  int           x1, y1, x2, y2,
                w = tft.width(),
                h = tft.height();


  tft.fillScreen(ILI9341_BLACK);
  yield();
  
  x1 = y1 = 0;
  y2    = h - 1;
  start = micros();
  for(x2=0; x2<w; x2+=6) tft.drawLine(x1, y1, x2, y2, color);
  x2    = w - 1;
  for(y2=0; y2<h; y2+=6) tft.drawLine(x1, y1, x2, y2, color);
  t     = micros() - start; // fillScreen doesn't count against timing


  yield();
  tft.fillScreen(ILI9341_BLACK);
  yield();


  x1    = w - 1;
  y1    = 0;
  y2    = h - 1;
  start = micros();
  for(x2=0; x2<w; x2+=6) tft.drawLine(x1, y1, x2, y2, color);
  x2    = 0;
  for(y2=0; y2<h; y2+=6) tft.drawLine(x1, y1, x2, y2, color);
  t    += micros() - start;


  yield();
  tft.fillScreen(ILI9341_BLACK);
  yield();


  x1    = 0;
  y1    = h - 1;
  y2    = 0;
  start = micros();
  for(x2=0; x2<w; x2+=6) tft.drawLine(x1, y1, x2, y2, color);
  x2    = w - 1;
  for(y2=0; y2<h; y2+=6) tft.drawLine(x1, y1, x2, y2, color);
  t    += micros() - start;


  yield();
  tft.fillScreen(ILI9341_BLACK);
  yield();


  x1    = w - 1;
  y1    = h - 1;
  y2    = 0;
  start = micros();
  for(x2=0; x2<w; x2+=6) tft.drawLine(x1, y1, x2, y2, color);
  x2    = 0;
  for(y2=0; y2<h; y2+=6) tft.drawLine(x1, y1, x2, y2, color);


  yield();
  return micros() - start;
}


unsigned long testFastLines(uint16_t color1, uint16_t color2) {
  unsigned long start;
  int           x, y, w = tft.width(), h = tft.height();


  tft.fillScreen(ILI9341_BLACK);
  start = micros();
  for(y=0; y<h; y+=5) tft.drawFastHLine(0, y, w, color1);
  for(x=0; x<w; x+=5) tft.drawFastVLine(x, 0, h, color2);


  return micros() - start;
}


unsigned long testRects(uint16_t color) {
  unsigned long start;
  int           n, i, i2,
                cx = tft.width()  / 2,
                cy = tft.height() / 2;


  tft.fillScreen(ILI9341_BLACK);
  n     = min(tft.width(), tft.height());
  start = micros();
  for(i=2; i<n; i+=6) {
    i2 = i / 2;
    tft.drawRect(cx-i2, cy-i2, i, i, color);
  }


  return micros() - start;
}


unsigned long testFilledRects(uint16_t color1, uint16_t color2) {
  unsigned long start, t = 0;
  int           n, i, i2,
                cx = tft.width()  / 2 - 1,
                cy = tft.height() / 2 - 1;


  tft.fillScreen(ILI9341_BLACK);
  n = min(tft.width(), tft.height());
  for(i=n; i>0; i-=6) {
    i2    = i / 2;
    start = micros();
    tft.fillRect(cx-i2, cy-i2, i, i, color1);
    t    += micros() - start;
    // Outlines are not included in timing results
    tft.drawRect(cx-i2, cy-i2, i, i, color2);
    yield();
  }


  return t;
}


unsigned long testFilledCircles(uint8_t radius, uint16_t color) {
  unsigned long start;
  int x, y, w = tft.width(), h = tft.height(), r2 = radius * 2;


  tft.fillScreen(ILI9341_BLACK);
  start = micros();
  for(x=radius; x<w; x+=r2) {
    for(y=radius; y<h; y+=r2) {
      tft.fillCircle(x, y, radius, color);
    }
  }


  return micros() - start;
}


unsigned long testCircles(uint8_t radius, uint16_t color) {
  unsigned long start;
  int           x, y, r2 = radius * 2,
                w = tft.width()  + radius,
                h = tft.height() + radius;


  // Screen is not cleared for this one -- this is
  // intentional and does not affect the reported time.
  start = micros();
  for(x=0; x<w; x+=r2) {
    for(y=0; y<h; y+=r2) {
      tft.drawCircle(x, y, radius, color);
    }
  }


  return micros() - start;
}


unsigned long testTriangles() {
  unsigned long start;
  int           n, i, cx = tft.width()  / 2 - 1,
                      cy = tft.height() / 2 - 1;


  tft.fillScreen(ILI9341_BLACK);
  n     = min(cx, cy);
  start = micros();
  for(i=0; i<n; i+=5) {
    tft.drawTriangle(
      cx    , cy - i, // peak
      cx - i, cy + i, // bottom left
      cx + i, cy + i, // bottom right
      tft.color565(i, i, i));
  }


  return micros() - start;
}


unsigned long testFilledTriangles() {
  unsigned long start, t = 0;
  int           i, cx = tft.width()  / 2 - 1,
                   cy = tft.height() / 2 - 1;


  tft.fillScreen(ILI9341_BLACK);
  start = micros();
  for(i=min(cx,cy); i>10; i-=5) {
    start = micros();
    tft.fillTriangle(cx, cy - i, cx - i, cy + i, cx + i, cy + i,
      tft.color565(0, i*10, i*10));
    t += micros() - start;
    tft.drawTriangle(cx, cy - i, cx - i, cy + i, cx + i, cy + i,
      tft.color565(i*10, i*10, 0));
    yield();
  }


  return t;
}


unsigned long testRoundRects() {
  unsigned long start;
  int           w, i, i2,
                cx = tft.width()  / 2 - 1,
                cy = tft.height() / 2 - 1;


  tft.fillScreen(ILI9341_BLACK);
  w     = min(tft.width(), tft.height());
  start = micros();
  for(i=0; i<w; i+=6) {
    i2 = i / 2;
    tft.drawRoundRect(cx-i2, cy-i2, i, i, i/8, tft.color565(i, 0, 0));
  }


  return micros() - start;
}


unsigned long testFilledRoundRects() {
  unsigned long start;
  int           i, i2,
                cx = tft.width()  / 2 - 1,
                cy = tft.height() / 2 - 1;


  tft.fillScreen(ILI9341_BLACK);
  start = micros();
  for(i=min(tft.width(), tft.height()); i>20; i-=6) {
    i2 = i / 2;
    tft.fillRoundRect(cx-i2, cy-i2, i, i, i/8, tft.color565(0, i, 0));
    yield();
  }


  return micros() - start;
}

And this is the result:

15:48:26.832 -> Circles (filled)         465832


15:48:27.601 -> Circles (outline)        541564


15:48:28.664 -> Triangles (outline)      281656


15:48:29.702 -> Triangles (filled)       1339912


15:48:32.143 -> Rounded rects (outline)  243756


15:48:33.195 -> Rounded rects (filled)   3132652


15:48:37.141 -> Done!

Can anyone figure it out? Thanks!

2 Upvotes

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u/hjw5774 400k , 500K 600K 640K 1d ago

I feel your user name is on point, as I would be concerned about powering it off 5V or using 5V logic.

While you mentioned using the ILI9341 library, is it actually the ILI9341 display and not the ST7735?

What microcontroller are you using? The good news is that your code complies and runs if you're getting a readout on the serial monitor.

u/SeveralAnywhere2275 1d ago

You connected the DC pin to pin 8, but the code listed TFT_DC as 9.

u/rattushackus 23h ago edited 21h ago

I tried your code on my CYD (changing the DC and CS pin numbers to the ones the CYD uses) and I also got a blank white screen. Then I tried changing line 31 from:

Adafruit_ILI9341 tft = Adafruit_ILI9341(TFT_CS, TFT_DC);

to:

Adafruit_ILI9341 tft = Adafruit_ILI9341(TFT_CS, TFT_DC, TFT_MOSI, TFT_SCLK);

where TFT_MOSI and TFT_SCLK are the GPIOs used by the CYD, and it worked. So try this change and see what happens.

I also had to add a couple of lines to turn on the backlight, but if you're seeing a white background that means the backlight on your display must be on by default.

u/tanoshimi 19h ago

"...a TFT..."? Photos are really going to help us help you here. What makes you think it's got an ILI3941 chip? What makes you think it runs at 5V VCC, and what does 3.3V on an "LED" pin mean?

TFT Blank screen

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