Features:
- 6 output channels
- Master BPM
- Separate divider or multiplier per chennel (from /32 to x24)
- Per-channel random pulse skip (currently only 50/50 chance)
- 2 inputs for external modulation (currently only 1, hardcoded to channel 6)

TODO:
- per-channel modulation settings
- different chance options for random
- External clock
- Save state to EEPROM when stopped
- swing
- Switch to U8G2 for screen
- settings (input mode, pulse length)
- Design PCB

Timer library available here
https://github.com/PaulStoffregen/FlexiTimer2

KiCad SSD1306 display component
https://github.com/pforrmi/KiCad-SSD1306-128x64