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

CrossRoads May 5, 2014, 6:09pm 4

Are the Gnds between the boards connected when powered by 12V?

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