If you want a truly unique sound out of your guitar, you can solder your own pedal together for infinite number of possibilities. If, however, you want to change things around, you’ll need to break out the soldering iron again and go to work.
The Pedal Pi by ElectroSmash — who you may recall from their earlier Arduino pedalSHIELDs— now presents another option, by integrating a Raspberry Pi Zero into the pedal itself. This allows it to be programmed with new effects, and you can even share your audio creations with the world via their forum!
Similar to its Arduino shields, the ElectroSmash’s new HAT consists of three parts:
The Input Stage: Amplifies and filters the guitar signal making it ready for the ADC (Analog do Digital Converter). The ADC sends the signal to the Pi Zero using SPI communication. In the forum the topic “Using MCP3202 ADC with Raspberry Pi Zero” gives more details about the ADC-Pi Zero connection.
Pi Zero: It takes the digitalized audio waveform from the ADC and does all the Digital Signal Processing (DSP) creating effects (distortion, fuzz, delay, echo, tremolo…). In the forum the topic “Basics of Audio DSP in C for Rapsberry Pi Zero” can assist you to learn the basics.
The Output Stage: Once the new digital waveform is created, the Pi Zero creates an analogue signal with two PWMs combined, the signal is filtered and prepared to be sent to the next pedal or the guitar amp. For more info check the topic “PWM Audio on Raspberry Pi Zero”.
The Pedal Pi is available in several kit variations, or since it’s open source, you could even build your own from scratch.