bela pedal

This is a programmable digital fx pedal, built using a bela mini.

I built it and did the hardware design, and I use it to perform with and to develop audio effects in C++.

This is my second pedal project using bela, with changes based on my experience using the older version that I built in 2017. The older version used a full-size bela board and was all hand wired, so it was a very tight fit! This made it tricky to modify and repair if anything happened to the circuitry, or if I had to remove the bela for any reason.

The features and controls are similar to the first version of the pedal:

  • stereo audio i/o
  • 4 control knobs (programmable)
  • 2 light sensors (programmable)
  • 2 cv/expression pedal inputs
  • 4 toggle switches (programmable)
  • 2 digital i/o jacks (these override 2 of the toggle switches if used)
  • 5 push buttons (programmable)
  • 1 programmable footswitch
  • 1 bypass footswitch with LED indicator
  • 6 programmable LEDs
  • USB host and device jacks

Of course it also includes the Bela Mini, with it’s fantastic browser based IDE for programming!

A big difference is the lack of the analogue cv outputs, this is due to the switch to a bela mini instead of a full size bela. I found that I wasn’t using the cv outs at all as I was mainly using the pedal with my guitar, and using the mini freed up a lot of space.

For this version of the pedal I designed a pcb to interface between the bela and the control/display/io components. This allows the bela to attach via headers and to plug in and out for easy removal when necessary. It’s the biggest circuit board I’ve designed and was a great learning experience! Some pictures below of the finished board from the fab house, and the design process in KiCad.