Getting 2 arduinos to talk

Projects Networking, Protocols, and Devices
1

Hello all,

I have managed to get two arduino boards to talk to each other with a very simple sketch. I have connected the two boards via the rx & tx pins, but it only seems to work as long as the boards are powered via usb. As soon as I use a battery pack it fails to work?
The boards are close to each other leads are only 3" long.
Any ideas what could be causing the problem?

Thanks in advance for your help.

Mark

2

If you are using a separate battery supply for each board, remember to connect the grounds together. When using power from the USB ports, the grounds are already commonized.