Serial Communication - drawing data from the slave to an LED matrix

Projects Networking, Protocols, and Devices
2

You need to post your programs.

Also post an example of the message that you want to send from the Mega to the Uno (hope I have the direction correct).

The Mega has 4 HardwareSerial ports - which one are you using to talk to the Uno (hint, NOT Rx0 and Tx0).

Have a look at the examples in Serial Input Basics - simple reliable ways to receive data.

...R