I’m using an Arduino Nano 33 IoT, Sparkfun 16x2 SerLCD screen with qwic shield and qwic cable, 6 peristaltic motors, and a 12V external power supply. When I connect the setup to my laptop (12v power supply disconnected), the screen displays messages as intended. When I disconnect my laptop and connect the 12v power supply, the screen turns on but doesn’t display any messages. How do I fix this?
Those (Nano 33 IoT and SerLCD) are 3.3v devices; https://www.mouser.com/datasheet/2/34/A … 601144.pdf
It might be best to run the power to the boards completely separate (and at 3.3v); use a stepdown converter or similar to achieve this. Also note that it may require a mean well regulated power supply to function normally