I'm using an Arduino Nano SuperMini (https://www.aliexpress.com/item/1005009116430067.html) and an ISP display (https://www.aliexpress.com/item/1005005769316344.html). I wrote a simple code that prints text and draws a frame. When I power the device with a battery, the display shows normally, and when I power the device from a PC via USB, the image is still visible. Does anyone have any ideas?
So what is the problem? Can you share the code you wrote. please use the < code > tags above.
The screen itself has an image memory.
Capacitors on the supply do not bleed their charge instantly.
Not sure at what supply voltage the RAM looses all it's stored data.
Your code should reset the screen on power-up or write a black or colour image to it.
void setup() {
tft.fillScreen(ST77XX_BLACK); // clear screen
Leo..
I solved the problem. The PCB was designed incorrectly. The ISP display is powered by 3.3 V via the CJA1117B-3.3 LDO. This LDO only gets power from the battery, so the LCD does not work when the device is powered via USB. I have fixed the error for the next version. Thanks for your help.