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I have a Arduinio nano and a ATMEGA168. I'm using the ST7789 library. The sample code which comes with the library runs perfectly and runs the display when using the Nano, but the same code does nothing on the ATMEGA168. I'm using the official pin mappings, so I sure it isn't the pins. Any suggestions I could try, or will a ATMEAG168 not drive a TFT? EDIT: I'm using the library written for adafruit.

#include <Adafruit_GFX.h>    // Core graphics library
#include <Adafruit_ST7789.h> // Hardware-specific library for ST7789
#include <SPI.h>             // Arduino SPI library

enter image description here

on the nano I'm using:

  • D13 -> SCL
  • D11 -> SDA
  • D9 -> DC
  • D8 -> RES

on the ATmega:

  • 19 (PB5) -> SCL
  • 17 (PB3)-> SDA
  • 15 (PB1)-> DC
  • 14 (PB0)-> RES

ANSWER TO COMMENTS: Yes I mean the exact same code without changing the pin numbers. The pin numbers I use on the ATmega are just the same pins connected via the official atmega mapping here: https://www.arduino.cc/en/Hacking/PinMapping168

Yes the ATMega is running, I've used a logic probe on the output pins and there is output on the pin. I've run numerous other programs more sophisticated than blinking LED's and the chips are fine. The clock source is PB0 (pin 14) of the atmega. Reference pinouts in the above link.

I'm not using AC power, high frequencies, or switching subcircuits, so I didn't believe I needed any decoupling. Why do you believe there should be, and where do you believe they should be located?

EDIT: MORE INFO FOR COMMENTORS: I'm just trying to use the terminology written on the PCB. :) This is the best I can do and stay under the 2 meg limit for images.

EDIT 3:

Yes, I thought the same and swapped the screens. I also tried swapping all the wires, just in case, and moving everything to a different breadboard and power supply. In addition, I swapped out the atmega since I have a couple of them. It is perplexing.

enter image description here

/*
 * Interfacing Arduino with ST7789 TFT display (240x240 pixel).
 * Graphics test example.
 * This is a free software with NO WARRANTY.
 * https://simple-circuit.com/
 */
/**************************************************************************
  This is a library for several Adafruit displays based on ST77* drivers.
 
  Works with the Adafruit 1.8" TFT Breakout w/SD card
    ----> http://www.adafruit.com/products/358
  The 1.8" TFT shield
    ----> https://www.adafruit.com/product/802
  The 1.44" TFT breakout
    ----> https://www.adafruit.com/product/2088
  as well as Adafruit raw 1.8" TFT display
    ----> http://www.adafruit.com/products/618
 
  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 <Adafruit_GFX.h>    // Core graphics library
#include <Adafruit_ST7789.h> // Hardware-specific library for ST7789
#include <SPI.h>             // Arduino SPI library
 
// ST7789 TFT module connections
#define TFT_CS    10  // define chip select pin
#define TFT_DC     9  // define data/command pin
#define TFT_RST    8  // define reset pin, or set to -1 and connect to Arduino RESET pin
 
// Initialize Adafruit ST7789 TFT library
Adafruit_ST7789 tft = Adafruit_ST7789(TFT_CS, TFT_DC, TFT_RST);
 
float p = 3.1415926;
 
void setup(void) {
  Serial.begin(9600);
  Serial.print(F("Hello! ST77xx TFT Test"));
 
  // if the display has CS pin try with SPI_MODE0
  tft.init(240, 240, SPI_MODE2);    // Init ST7789 display 240x240 pixel
 
  // if the screen is flipped, remove this command
  tft.setRotation(2);
 
  Serial.println(F("Initialized"));
 
  uint16_t time = millis();
  tft.fillScreen(ST77XX_BLACK);
  time = millis() - time;
 
  Serial.println(time, DEC);
  delay(500);
 
  // large block of text
  tft.fillScreen(ST77XX_BLACK);
  testdrawtext("Lorem ipsum dolor sit amet, consectetur adipiscing elit. Curabitur adipiscing ante sed nibh tincidunt feugiat. Maecenas enim massa, fringilla sed malesuada et, malesuada sit amet turpis. Sed porttitor neque ut ante pretium vitae malesuada nunc bibendum. Nullam aliquet ultrices massa eu hendrerit. Ut sed nisi lorem. In vestibulum purus a tortor imperdiet posuere. ", ST77XX_WHITE);
  delay(1000);
 
  // tft print function!
  tftPrintTest();
  delay(4000);
 
  // a single pixel
  tft.drawPixel(tft.width()/2, tft.height()/2, ST77XX_GREEN);
  delay(500);
 
  // line draw test
  testlines(ST77XX_YELLOW);
  delay(500);
 
  // optimized lines
  testfastlines(ST77XX_RED, ST77XX_BLUE);
  delay(500);
 
  testdrawrects(ST77XX_GREEN);
  delay(500);
 
  testfillrects(ST77XX_YELLOW, ST77XX_MAGENTA);
  delay(500);
 
  tft.fillScreen(ST77XX_BLACK);
  testfillcircles(10, ST77XX_BLUE);
  testdrawcircles(10, ST77XX_WHITE);
  delay(500);
 
  testroundrects();
  delay(500);
 
  testtriangles();
  delay(500);
 
  mediabuttons();
  delay(500);
 
  Serial.println("done");
  delay(1000);
}
 
void loop() {
  tft.invertDisplay(true);
  delay(500);
  tft.invertDisplay(false);
  delay(500);
}
 
void testlines(uint16_t color) {
  tft.fillScreen(ST77XX_BLACK);
  for (int16_t x=0; x < tft.width(); x+=6) {
    tft.drawLine(0, 0, x, tft.height()-1, color);
    delay(0);
  }
  for (int16_t y=0; y < tft.height(); y+=6) {
    tft.drawLine(0, 0, tft.width()-1, y, color);
    delay(0);
  }
 
  tft.fillScreen(ST77XX_BLACK);
  for (int16_t x=0; x < tft.width(); x+=6) {
    tft.drawLine(tft.width()-1, 0, x, tft.height()-1, color);
    delay(0);
  }
  for (int16_t y=0; y < tft.height(); y+=6) {
    tft.drawLine(tft.width()-1, 0, 0, y, color);
    delay(0);
  }
 
  tft.fillScreen(ST77XX_BLACK);
  for (int16_t x=0; x < tft.width(); x+=6) {
    tft.drawLine(0, tft.height()-1, x, 0, color);
    delay(0);
  }
  for (int16_t y=0; y < tft.height(); y+=6) {
    tft.drawLine(0, tft.height()-1, tft.width()-1, y, color);
    delay(0);
  }
 
  tft.fillScreen(ST77XX_BLACK);
  for (int16_t x=0; x < tft.width(); x+=6) {
    tft.drawLine(tft.width()-1, tft.height()-1, x, 0, color);
    delay(0);
  }
  for (int16_t y=0; y < tft.height(); y+=6) {
    tft.drawLine(tft.width()-1, tft.height()-1, 0, y, color);
    delay(0);
  }
}
 
void testdrawtext(char *text, uint16_t color) {
  tft.setCursor(0, 0);
  tft.setTextColor(color);
  tft.setTextWrap(true);
  tft.print(text);
}
 
void testfastlines(uint16_t color1, uint16_t color2) {
  tft.fillScreen(ST77XX_BLACK);
  for (int16_t y=0; y < tft.height(); y+=5) {
    tft.drawFastHLine(0, y, tft.width(), color1);
  }
  for (int16_t x=0; x < tft.width(); x+=5) {
    tft.drawFastVLine(x, 0, tft.height(), color2);
  }
}
 
void testdrawrects(uint16_t color) {
  tft.fillScreen(ST77XX_BLACK);
  for (int16_t x=0; x < tft.width(); x+=6) {
    tft.drawRect(tft.width()/2 -x/2, tft.height()/2 -x/2 , x, x, color);
  }
}
 
void testfillrects(uint16_t color1, uint16_t color2) {
  tft.fillScreen(ST77XX_BLACK);
  for (int16_t x=tft.width()-1; x > 6; x-=6) {
    tft.fillRect(tft.width()/2 -x/2, tft.height()/2 -x/2 , x, x, color1);
    tft.drawRect(tft.width()/2 -x/2, tft.height()/2 -x/2 , x, x, color2);
  }
}
 
void testfillcircles(uint8_t radius, uint16_t color) {
  for (int16_t x=radius; x < tft.width(); x+=radius*2) {
    for (int16_t y=radius; y < tft.height(); y+=radius*2) {
      tft.fillCircle(x, y, radius, color);
    }
  }
}
 
void testdrawcircles(uint8_t radius, uint16_t color) {
  for (int16_t x=0; x < tft.width()+radius; x+=radius*2) {
    for (int16_t y=0; y < tft.height()+radius; y+=radius*2) {
      tft.drawCircle(x, y, radius, color);
    }
  }
}
 
void testtriangles() {
  tft.fillScreen(ST77XX_BLACK);
  int color = 0xF800;
  int t;
  int w = tft.width()/2;
  int x = tft.height()-1;
  int y = 0;
  int z = tft.width();
  for(t = 0 ; t <= 15; t++) {
    tft.drawTriangle(w, y, y, x, z, x, color);
    x-=4;
    y+=4;
    z-=4;
    color+=100;
  }
}
 
void testroundrects() {
  tft.fillScreen(ST77XX_BLACK);
  int color = 100;
  int i;
  int t;
  for(t = 0 ; t <= 4; t+=1) {
    int x = 0;
    int y = 0;
    int w = tft.width()-2;
    int h = tft.height()-2;
    for(i = 0 ; i <= 16; i+=1) {
      tft.drawRoundRect(x, y, w, h, 5, color);
      x+=2;
      y+=3;
      w-=4;
      h-=6;
      color+=1100;
    }
    color+=100;
  }
}
 
void tftPrintTest() {
  tft.setTextWrap(false);
  tft.fillScreen(ST77XX_BLACK);
  tft.setCursor(0, 30);
  tft.setTextColor(ST77XX_RED);
  tft.setTextSize(1);
  tft.println("Hello World!");
  tft.setTextColor(ST77XX_YELLOW);
  tft.setTextSize(2);
  tft.println("Hello World!");
  tft.setTextColor(ST77XX_GREEN);
  tft.setTextSize(3);
  tft.println("Hello World!");
  tft.setTextColor(ST77XX_BLUE);
  tft.setTextSize(4);
  tft.print(1234.567);
  delay(1500);
  tft.setCursor(0, 0);
  tft.fillScreen(ST77XX_BLACK);
  tft.setTextColor(ST77XX_WHITE);
  tft.setTextSize(0);
  tft.println("Hello World!");
  tft.setTextSize(1);
  tft.setTextColor(ST77XX_GREEN);
  tft.print(p, 6);
  tft.println(" Want pi?");
  tft.println(" ");
  tft.print(8675309, HEX); // print 8,675,309 out in HEX!
  tft.println(" Print HEX!");
  tft.println(" ");
  tft.setTextColor(ST77XX_WHITE);
  tft.println("Sketch has been");
  tft.println("running for: ");
  tft.setTextColor(ST77XX_MAGENTA);
  tft.print(millis() / 1000);
  tft.setTextColor(ST77XX_WHITE);
  tft.print(" seconds.");
}
 
void mediabuttons() {
  // play
  tft.fillScreen(ST77XX_BLACK);
  tft.fillRoundRect(25, 10, 78, 60, 8, ST77XX_WHITE);
  tft.fillTriangle(42, 20, 42, 60, 90, 40, ST77XX_RED);
  delay(500);
  // pause
  tft.fillRoundRect(25, 90, 78, 60, 8, ST77XX_WHITE);
  tft.fillRoundRect(39, 98, 20, 45, 5, ST77XX_GREEN);
  tft.fillRoundRect(69, 98, 20, 45, 5, ST77XX_GREEN);
  delay(500);
  // play color
  tft.fillTriangle(42, 20, 42, 60, 90, 40, ST77XX_BLUE);
  delay(50);
  // pause color
  tft.fillRoundRect(39, 98, 20, 45, 5, ST77XX_RED);
  tft.fillRoundRect(69, 98, 20, 45, 5, ST77XX_RED);
  // play color
  tft.fillTriangle(42, 20, 42, 60, 90, 40, ST77XX_GREEN);
}
Improve this question
5
  • "will a ATMEAG168 not drive a TFT?". An ATMega168 can be used with all kinds of displays. But somehow I don't think that's the question you actually wanted answered. To give a useful answer beyond that, more details are needed. Which exact library? What version of it? Which example? How exactly did you wire it?
    – timemage
    Feb 10, 2021 at 1:07
  • If you say "the same code", do you mean without changing the pin numbers in the source?
    – the busybee
    Feb 10, 2021 at 13:00
  • Do you know if your ATMega168 is actually even running? How are the fuses configured? What is your clock source? Also: where are your decoupling capacitors? I think the problem is not that it can't control the screen, but that it just can't run full-stop. Start by making the 168 blink an LED...
    – Majenko
    Feb 10, 2021 at 13:22
  • You appear to be confusing I2C and SPI terminology. What you're calling SCL and SDA are SCK and MOSI respectively. The wiring image is very low resolution. Not useless, but pretty bad. It is a good angle and everything is in frame. If you could replace with a better resolution image and show what code you're using that would be helpful.
    – timemage
    Feb 10, 2021 at 17:22
  • Well, I've been through your wiring and through the library, and if you have the same sketch running on both, I'm not seeing why it wouldn't work. As a sanity check you might swap the displays and make sure the problem doesn't follow the display. I don't have a good reason for thinking that it will, but is a very simple test to rule that out.
    – timemage
    Feb 11, 2021 at 3:20

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