I wanted a way to control my music from my bedside table when I’m half awake in the dark. The receiver of course comes with a perfectly fine IR remote. But it has about two dozen mushy membrane buttons, and you have to aim it at the receiver for it to work. We can do better!
NAD receivers of this era (and maybe today, I’m not sure) feature a special connector in the back that lets you daisy-chain different NAD components and let them share IR remote commands with each other. It’s nothing fancy - just a single RCA connector on the back, which they label “NADLink”. You connect two components together with a basic two-conductor RCA cable and you’ll all set.
As it turns out, the protocol that NADLink uses is just a rehashed version of the NEC remote control protocol, where instead of IR pulses it uses 5V TTL. We can hack this!
With some help from the internet (thanks Morten Hustveit and Bitraf), I was able to reverse-engineer the protocol, and program a little protoboard (a Feather M0) to send the commands I was interested in (volume, input switching, mute etc).
The hardware is pretty simple, but still a big improvement on the squishy IR remote: a nice, big metal knurled knob, connected to a tactile rotary encoder, along with a little piezoelectric speaker for some subtle audio feedback.
Yes, I know, it needs a case! That’ll happen some day.