So I'm having trouble getting any Arduino to send or receive serial communication when not plugged into my PC with the port selected. Even so, I have to upload the code each time after trying to power it externally.
What happens is that it will work when plugged into the PC (the TX is rapidly flashing because the code is sending nonstop), but when I power it externally with any 5V adapter (power via usb or barrel), all serial function stops. This is the point where I have to refresh it by uploading the code again. I've tried sketches that I've used before, which I know work, and I'm having the same exact results, even over multiple boards (new ones and ones I've been using).
Is there some setting that I'm not thinking of or what? Any input on this is appreciated, thanks!