Introduction: Raspberry Pi Zero Guitar Pedal

Pedal-Pi is a lo-fi programmable guitar pedal that works with the Raspberry Pi ZERO Board. The project is totally Open Source & Open Hardware and made for hackers, programmers and musicians that want to experiment with sounds and learn about digital audio.

You can code your own effects using standard C and get inspiration from the ready-to-use effects from the forum, like the Clean/Transparent, Booster/Volume, Distortion, Fuzz, Delay, Echo,Octaver, Reverb, Tremolo, Looper, etc.

Specifications.

  • Based in Raspberry Pi Zero (1GHz ARM11 core).
  • Analog stages using MCP6002 rail-to-rail operational amplifier.
  • ADC: 12bits / Sampling Rate 50Ksps (MCP3202).
  • Output Stage: 12 bits (2x6bits PWMs running in parallel)
  • Pi Zero:
    • 1GHz ARM11 core.512MB of LPDDR2 SDRAM.
    • Micro-SD card slot.
  • Interface:
    • 2 Configurable push buttons.
    • 1 Configurable toggle switch.
    • 1 programmable blue led
    • .True Bypass Foot-switch.
  • Connectors:
    • Input Jack, 1/4 inch unbalanced, Zin=1MΩ.
    • Output Jack, 1/4 inch unbalanced, Zout=100Ω.
    • Power supply: power taken from the Pi Zero board (micro-USB).

Step 1: Step 1: Get the Components and the PCB.

Picture of Step 1: Get the Components and the PCB.

The electronic components are all through-hole and easy-to-find. You can see the complete list of components here:

For the PCB you can find in the forum a PDF with the transfer files so you can do the PCBs at home, also in the EletroSmash Store there are PCBs for sale:

Step 2: Step 2: Soldering the Circuit.

Picture of Step 2: Soldering the Circuit.

There is manual that explains how to build the Pedal-Pi step by step with photographs and detailed information:

There is a topic in the forum for any additional question.There is also a Flickr gallery with high-res photos of each step.

Step 3: Step 3: a Closer Look to the Circuit.

Picture of Step 3: a Closer Look to the Circuit.

There is a detailed analysis of the Pedal-Pi Circuit in the forum:

This hat has 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".

Step 4: Step 4: Start Programming!

Picture of Step 4: Start Programming!

Check the "How to Start Programming Pedal-Pi" guide. It is a short guide to start coding this Raspberri Pi Zero guitar pedal. The aim is to understand the basic ideas and then progress as fast as possible through a series of examples.

You are very welcome to upload your ideas and pedals to the forum!

Step 5: Step 5: Create Your Own Sounds.

Picture of Step 5: Create Your Own Sounds.

The best way to progress is to take the basic examples from the forum and try to modify them to fit your taste or set-up. Just changing some values or parameters can make a great difference.

Once you have understood the basic examples, you can think about how to create your own new pedals (reverse delay? reverse-echo?) or mixing some of the examples (fuzz+echo? distortion+delay?). There are tons of unexplored effects to be discovered ;) !

There is a cool review by Blitz City DIY in YouTube: Pedal Pi Kit Review - A Raspberry Pi Zero Guitar Pedal

Comments

KumanT (author)2017-10-09

Nice project!

ElectroSmash (author)KumanT2017-10-11

Thanks!!! ;)

ihaveno (author)2017-10-06

would it work on a different Pi?

ElectroSmash (author)ihaveno2017-10-06

It works for sure with the Pi Zero and the Wireless Pi Zero, the code it is developed using the BCM2835 processor libraries.

This processor is also used in the Raspberry Pi Model A, B, B+ and the Compute Module.

Looking at the pinout, the Raspberry Pi 1B+ looks compatible in theory it should work but in practise nobody tried yet.

JonathanC96 (author)2017-10-06

Could this work with an Orange Pi One?

ElectroSmash (author)JonathanC962017-10-06

Ive never tried... I am afraid that it wont probably work with the Orange Pi.

JackS2SF (author)2017-10-03

This is stellar! Any recommendations of where in the States to buy all the parts? Think it's attainable for someone with zero programming knowledge like myself or is this too hard of a first project?

BlackoutXIII (author)JackS2SF2017-10-04

The BOM gives part number for Mouser... or, you can order a kit from Electrosmash (linked in the article).

JackS2SF (author)BlackoutXIII2017-10-04

Darn, not helpful; so only European suppliers then? Naturally I had checked the Electrosmash page as I read the article and clicked in the links already but would prefer not to order from so far away with 9 business days to ship, ouch. Worth the wait I guess but still a bummer. Thanks anyways.

ElectroSmash (author)JackS2SF2017-10-04

We send from UK, but so far all the US shippings go pretty smooth (besides the 9 days shipping time)... If you have any question just drop us an email!

Batmantwo (author)2017-10-04

Any suggestions on where to buy in Australia???

ElectroSmash (author)Batmantwo2017-10-04

We provide the Bill of Materials with Mouser references and in the forum you can find the PCB transfers so you can do all DIY at home.

We also have the PCB and complete kits in the store: http://www.electrosmash.com/store/

desposito adinolfi (author)2017-10-03

When you plug the power cable in the pi zero, it execute the program automatically? How?

DejayRezme (author)2017-10-03

Wow this is an awesome idea! Thanks for sharing!

I guess I could integrate this into a guitar body and add a speaker amp (like those DIY bluetooth amps) to it and have a powered e-guitar with multiple effects? I haven't played e-guitar in years but that idea fascinates me.

ElectroSmash (author)DejayRezme2017-10-03

Yes, that is a cool idea ;), you can use the Pedal-Pi and connect the output to a simple LM386 amplifier like the Smokey Amp or as you said get a cheap eBay DIY bluetooth amp.

faustologa (author)2017-10-03

Hey great contribution, thank you so much! I was wondering if you think this could be useable as a vocal effects pedal instead, like adding real-time vocal harmonies and so. If so, how would you go about doing that?

ElectroSmash (author)faustologa2017-10-03

Hi, I did not try to connect a microphone to it yet, but the pedalSHIELD DUE circuit is pretty similar and we connected a Shure SM57 microphone without problems, so in theory it should work the same for the Pedal-Pi, have a look at this:

https://www.electrosmash.com/forum/hardware-pedalshield/39-connecting-a-microphone-to-pedalshield

gm280 (author)2017-09-30

Nice setup. Can you switch from one sound to another easily? I mean since it is preprogrammed, can you push a switch to the sound you want, or are they in a serial sequenced step setup?

DIY Hacks and How Tos (author)2017-09-30

Nice DIY pedal.

Thanks!!