Hello, I used the example code on the library of ST7789_Fast by cbm80amiga I watch a video tutorial supposedly it will display something but when I try it shows no display. so what is the issue?
You get a backlight simply by connecting GND and putting a positive voltage on the backlight pin.
Why you don't have any display: to start with, 5V level signals into a display expecting 3.3V level signals. And no, I'm not talking about the display's power pin, but the signal pins (SDA, SCL, DC, RES). The display is almost certainly a 3.3V device and requires level shifters to work with a 5V board.
I put the voltage at 3.3V but still no display text
As I said, I'm not talking about the display's power pin.
You may have connected 3.3V to the display's Vcc pin, but the signal pins (SCL, SDA, RES and DC) are still being fed by 5V level signals. The ST7789 is a 3.3V device and needs 3.3V level signals.
Okay, thank you. I finally understand what you were saying.
rather than using multiple level converters to get the display to work with a UNO it is probably simpler to move to a microcontroller which uses 3.3V logic, e.g. ESP32
using TFT_eSPI library