TFT ST7789v3 Problems with display

Other Hardware Displays
1

Hi, these day I've bought this tft display on AliExpress. When I got the chance to build the circuit an test it properly I've got some problems. The backlight of the display blinks everytime some command is passed from the controller. But nothing shows off, only the backlight(with no color defined).
In the picture the wiring is a mess, so there's the explanation (i'm using arduino uno).
GND -> GND
VCC -> 3.3V
SCL -> SCL
SDA -> SDA
RES -> PIN8
DC -> PIN9
CS -> PIN10
BLK -> NC

circuit
circuit976×1258 124 KB

display_back
display_back1075×1259 120 KB

display_front
display_front1024×1280 84.8 KB

There's the code, just trying a pretty basic one.

#include <Adafruit_GFX.h>
#include <Adafruit_ST7789.h>
#include <SPI.h>
#define CS  10
#define DC  9
#define RES 8

Adafruit_ST7789 tft = Adafruit_ST7789(CS, DC, RES);

void setup() {
  Serial.begin(9600);

  tft.init(240, 280);
  tft.setRotation(1);

  tft.fillScreen(ST77XX_RED);
  delay(1000);
  tft.fillScreen(ST77XX_BLACK);
  delay(1000);
  tft.setCursor(0, 0);
  tft.setTextColor(ST77XX_WHITE);
  tft.setTextSize(2);
  tft.print("HELLO");

}

void loop() {
  
}
2

I would put money on that display having an SPI interface, despite the SDA/SCL labels. The CS and DC pins are a giveaway.

Also, the library uses SPI.

Hook the display's SDA pin up to the Uno's MOSI pin (11) and the display's SCL pin up to the Uno's SCK pin (13) and give that a try.

3

I had already done that and it didn't work. Now I tried it to confirm, I can't believe it but it actually worked... thank you very much. :smiley:

4

I know this topic is a bit stale from earlier this year, but I would like to ask if you are feeding the Uno's 5-volt logic levels directly to the display's control/data lines?? I have done this successfully for years with the ST7735 displays, but have not tried it with a ST7789 interface.