https://forum.arduino.cc/t/arduino-mega-and-rainbowuino-v2-0/19690
Arduino Mega and Rainbowuino v2.0 - Interfacing - Arduino Forum
Sep 6, 2010 - Hi, I am attempting to program a Rainbowuino v2.0 with an Arduino Mega. I have connected up the tx-tx and rx-rx and other wires as specified, but I am having...
arduino megainterfacingforum