Hi all - I got 2 arduino, one nano and one Mega, talking to each other by serial. It's working fine when my laptop is usb-connected to my Mega. But when I unplug the USB cable and power the Mega with a DC adapter 12V, the serial does not seems to work.

Serial1 on mega not working when power by adapter

robtillaart May 1, 2014, 8:12pm 2

can you measure if the voltages on the board are the same (powered by USB vs powered by adapter)

do other parts (leds) work as expected?

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