relay-bypass VS ATtiny84-TinyCalibrator

Not to discourage it, but FYI on what's already out there for AVR: https://github.com/mstratman/relay-bypass

All open source: https://github.com/mstratman/relay-bypass

u/cedarcedar If you're curious you can see its code here: https://github.com/mstratman/relay-bypass/blob/main/relay-bypass/relay-bypass.ino

if you find momentary buttons that are suitable, use them to control a relay. e.g. with this kit or from scratch.

An alternate option, which you probably also won't find an off-the-shelf solution for, is to use a microcontroller and a couple of relays. You can steal 90% of the bones from my project here: https://github.com/mstratman/relay-bypass Switch to an attiny84 or something else with more pins, add a second foot switch, get rid of the muting, and add the toggle logic.

Tonight I added an EQD-style relay bypass using a MAS Effects kit to somebody's pedal and took a few pics to share in case anyone's interested in seeing how you do this sort of upgrade (disclaimer, shameless self promotion, but FYI it's also open source). It's a good first project for anyone wanting to dip their toe in the DIY pedal waters.

Or if you want to completely DIY the MAS Effects one without a kit, all the code and schematics are here: https://github.com/mstratman/relay-bypass (but again, check parts availability first since the relays and AVR are hard to find).

[schematics, code, etc are all here] [kits here]

The footswitch controls a relay that's powered by the code from this project: https://github.com/mstratman/relay-bypass (from which you can buy drop-in kits to get soft touch true bypass on your pedals). This one has a bigger, cheaper relay since space wasn't at a premium the way it is on those drop-in kits.

Schematic: https://github.com/mstratman/relay-bypass/blob/main/relay-bypass-schematic-1.3.png