I would have loved to do this on a real ArduBoy, but they appear to be unavailable until middle of this year. So, I bought a cheap clone DuinoBoy, as it wouldn’t matter if I stuffed it up.
This is a clone of a clone of a Gameboy which I have modified to have stereo audio out and a sync pulse so it can sync Pocket Operators, Volcas, etc…
The Arduboy system is awesome and makes it relatively easy to program the Clone (DuinoBoy) to play music. Unfortunately the Clone only has one pin connected the buzzer so I added two line outs.
I am using the Arduboy environment and the BeepPin1 and BeepPin2 classes to make sounds (square Waves) which go separately to the left and right channels of the output. Unfortunately, the clone has no pads to make hacking it easy, I had to solder one wire directly to the chip, which was a bit nerve-racking for me and my dodgy soldering skills. The pins for the speaker are PC6 and PC7 on the ATMega32U4.
I send a 15ms pulse at the start of each note to pin PD2 (digital pin 0) which is connected to the sync out socket. (Tip not ring to match the Pocket Operators spec)
If anyone is interested in the code, check out my GitHub:
There is a picture of the modication on the GitHub: