Troubleshooting instructions

[zenMaya]

Hi, I've been trying to work out why my redox doesn't work.

I have flashed each half with firmware, the receiver and the arduino. All went fine. But when I try to connect the whole keyboard together nothing happens. I suspect there's something wrong with the receiver, but I cannot tell what. Only D4 is faintly glowing, but other than that all leds are off (except for the arduino one, which is glowing red)

Is there some way of the arduino to print debug messages, like if it found the connected keyboard half, or it cannot comm with the wireless chip?

I'm really lost on what to do now. I don't think there are any shorts. I really wish there were some troubleshooting instructions, just general ones. For example one of my issues was that I wasn't able to upload firmware to the YJ chip, it turned out that the ground pin wasn't properly connected, but the issue appeared like a failed firmware flash.