A Maker by the name of J Rodriguez has designed an open source guitar pedal with KiCad. Users of the device can program their own effects in C/C++ or download ready effects from an online library.
pedalSHIELD – which plugs directly into an Atmel-powered Arduino Due (SAM3X8E ARM Cortex-M3) – allows users to learn about digital signal processing, effects and synthesizers without extensive knowledge of electronics or programming.
So, how does pedalSHIELD work? Well, according to Rodriguez, the guitar input signal is amplified and sent to the Arduino for processing. The Atmel-based Arduino Due is then tasked with Digital Signal Processing (DSP), which includes modifying the signal and adding effects (delay, echo, distortion, volume). Once the waveform is processed, the signal is relayed from the Arduino DACs to the guitar (summing) amp.
pedalSHIELD uses 2 ADCs and 2 DACS in parallel to achieve higher bit resolution (2 x 12bits). However, a 1 DAC- 1ADC is also possible without additional mods.
The pedalSHIELD currently includes a custom 3D printed cover designed and manufactured by Shuttl3d. Made of ABS plastic with 3mm thickness, the cover protects the electronic circuits while adding a touch of color to the pedal.