I have modified a DuinoBoy. This is a clone of a Arduboy 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.
Details:
Audio:
I am using the BeepPin1 and BeepPin2 class 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.
Sync:
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)
Code on GitHub:
Modification (which could be done to Arduboy I think): There is a picture on GitHub of the back of the DuinoBoy showing where I soldered wires.
Here is a demonstration of it in action on YouTube:
The ArduBoy is a great idea. Thanks for developing it.