If I am only interfacing two arduinos can I simply connect the to each other via the tx and rx lines?
If so, do I need any external hardware or just wires between them (e.g. tx0->rx1 tx1->rx0)
and then I can send messages from one arduino to the other via the normal serial.print method?
I was planning to use I2C but I am short on pins and implementing I2C will cause me to shift around a lot of stuff. My communication is pretty simple as well and is unidirectional. i.e. The master arduino is sending short messages to the slave but not vice versa.