This is the source code to my original Synth Cable using an ATtiny85. It's also identical to the code that runs on my World's Smallest MIDI Synthesizer and almost identical to that used in the Hardware Reverse Oscilloscope.
It has a monophonic square wave output and supports an arpeggiator, modulation/aftertouch and pitch-bend.
- Responds to Note On / Note Off on Channel 1 only
- CC1/Aftertouch controls modulation depth
- CC5 controls modulation speed
- CC7 controls arpeggiator speed
Schematics and explanation here: https://mitxela.com/projects/midi_on_the_attiny
Video demos:
Code last modified 5th Aug 2015.