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pi-stomp_v1

pi Stomp! DIY Multi-effects for Guitar

Click here for pi-Stomp Core

Finally, you can build your own high-definition multi-effects pedal!

pi Stomp is an open source high definition multi-effects stompbox platform. The base install contains over 350 plugins - effects, modeled amps, loopers and sound generators. It was designed for guitar and bass, but works great for processing electronic instruments as well.

It sports 24-bit, 48 to 96kHz stereo audio and a Raspberry Pi 64-bit quad core processor running at 1.4 GHz

Numerous virtual pedalboards containing up to dozen or more plugins, can be constructed via MOD, a super powerful yet easy to use drag-n-drop web user interface. Each pedalboard can be saved with multiple “presets”, each being a snapshot of all the parameters for a given sound.

Once your pedalboards are saved, only the pi Stomp is needed on-stage or in the studio.

An LCD shows an overview of the current pedalboard, navigation via rotary encoder.

Example Use

Plugins/Effects included (base install)

  • 57 Overdrive, Distortion and Fuzz
  • 23 Dynamic (Compressor, Limiter, DeEsser)
  • 35 Filter (EQ, Filters, Wah, etc.)
  • 46 Generator (Synth, Sampler, Drumkit, General Midi modules, etc.)
  • 31 Modulation (Chorus, Flanger, Phaser, Ring Modulation, Rotary, Tremolo, Vibrato, etc.)
  • 15 Reverb
  • 24 Delay
  • 29 Simulator (Preamps, Amps, Cabinets)
  • 8 Spacial (Stereo panning and imaging)
  • 20 Spectral (Pitch Shifting, Doubler, Harmonizer, Vocoder)
  • 22 Utility (Midi, Noisegate, Gain, Phrase Looper, Sequencer, Switching, Tuner, etc.)

Why pi Stomp?


When it comes to amp modeling and effect processing, we’re in a golden age for guitarists. The choices for gear are almost endless. Why do we need another?

Well, almost all of the available solutions are based on proprietary platforms. pi Stomp is open source software running on hardware that You built.

Being a more open and general purpose platform, you can hack or extend it by:

  • Importing additional effect or synth plugins
  • Coding your own plugins. Create that Tremo-Transmogrifier-Drive'u'luxe you’ve dreamt of!
  • Adding additional audio software. If it runs on linux, it’ll likely run on pi Stomp and you could mix in the audio via the onboard alsa mixer.
  • Modifying the Pi-Stomp software. It’s all on github. So clone it, fork it, and do what you will to make it work for you. Add/change what’s displayed on the LCD, have the footswitches send IOT or DMX512 message packets via USB or WiFi to control your stage lighting.
  • Moding, extending or upgrading the hardware. Major components (CPU, Audio Card and LCD) are connected via the standard 40-pin Raspberry Pi GPIO connector and use standard protocols (SPI and I2C). Theoretically, you could increase your processing power by plugging in the forthcoming Raspberry Pi 4.0! Or swap in a new pi-Zero format sound card. Or upgrade to color/higher res graphics by swapping the LCD.

Is pi Stomp better than HX Stomp, Headrush, Mod Duo, etc.?

It certainly is more hackable and upgrade-able! Performance wise, it's very close in many regards, and even has some unique features. But in general, if you're not the DIY type, or if you want a pro quality product, please buy one those. Each was designed by a large team, in a well funded company, and assembled in a production factory.

pi Stomp is a hobbyist project For hobbyists. If you’ve always wanted to build your own multi-effects unit, here’s your chance. I put my blood sweat and tears into it, so you can have the same enjoyment I have when I plug in and make awesome sounds thru something that I built. If you’ve ever built your own effect or amp, you know what I mean. Now imagine an entire do-anything pedalboard that conforms to your crazy musical ideas!

The flip-side is that you will need to invest some time and effort. Although the wiring is similar or even simpler than many stomp boxes, the circuit board assembly is rather advanced. Please see Building pi Stomp before purchasing parts.

Feature Comparison

pi-Stomp Core pi Stomp v1 (superseded by pi-Stomp Core) MOD Duo HX Stomp Headrush Gigaboard
Audio 24-bit 48kHz or 96kHz 24-bit 48kHz or 96kHz 24-bit 48kHz 24-bit 96kHz 24-bit 96kHz
Number of Plugins (FX, Models, etc.) 358+ (user upgrade-able) 358+ (user upgrade-able) 330+ (user upgrade-able) 200 (not upgrade-able) 107 (not upgrade-able)
Simultaneous Plugins Typ 12+ (depends on CPU demand) Typ 12+ (depends on CPU demand) Typ 12+ (depends on CPU demand) 6 12?
Plugin Routing Completely flexible Completely flexible Completely flexible Serial or two parallel Serial or two parallel
Plugin types Effects, Models, Generators, Loopers Effects, Models, Generators, Loopers Effects, Models, Generators, Loopers Effects, Models, Looper Effects, Models, Looper
DIN (5-pin) MIDI Optional In and/or Out In In & Out In & Out/Thru In & Out/Thru
USB MIDI In & Out In & Out In & Out None None
Expression Pedal Input Optional (up to 8 Analog controls) Yes No Yes Yes
Footswitches Optional (up to 13) 3 (user assignable) 2 (user assignable) 3 (multiple modes) 4 (multiple modes)
True Bypass Yes for Channel 1, Chan 2 always on Yes (latching relays - save state when powered off) Yes (mechanical relays) Yes (mechanical relays) Apparently Not
Audio Ins/Outs 2 in / 2 out (independent or stereo) 2 in / 2 out (independent or stereo) 2 in / 2 out (independent or stereo) 2 in / 2 out (stereo) 1 in / 2 out (stereo)
LCD Color! Monochromatic 2x Monochromatic Color Color / Touch
Can use as a USB audio interface Not currently (OTG required) Not currently (OTG required) Yes Yes Yes
Wireless Connectivity WiFi & Bluetooth WiFi & Bluetooth WiFi & Bluetooth None None
Software/Firmware Open Source/Hackable/Upgrade-able Open Source/Hackable/Upgrade-able Open Source/Upgrade-able Proprietary/Upgrade-able Proprietary/Upgrade-able
Hardware Very Hackable/Upgrade-able Hackable/Upgrade-able Proprietary/Expandable via port Fixed Proprietary Fixed Proprietary
Dimensions (in) 4 x 2.7 x 1.75 (w/o enclosure), 4.7 x 3.7 x 2.0 (smallest enclosure) 7.4 x 4.7 x 2.0 7.1 x 6.3 x 2.9 7.0 x 5.0 x 2.6 13.0 x 8.9 x 2.6
Cost $159 (without enclosure or other options) $198 (depends on sources) $550 $650 $599

Another product by the great folks at blokas.io named “pisound” (https://blokas.io/pisound/) is similar in core functionality to pi Stomp and MOD Duo. It's not listed in the table above because it lacks features which are generally required for a stomp box form factor. Pisound has only one footswitch, no bypass, no LCD, no robust enclosure, and only stereo (TRS) jacks with rather low input impedance (100k ohm). But, for a table based mutlti-effect unit, or if keyboards are more your game, it's worth checking out.

What about sound quality and the elusive ultimate guitar tone?

With 24-bit 96kHz I/O and a quad core 1.4 GHz processor, pi Stomp certainly has the processing power to rival the some of the best units. A vast number of current commercial recordings have been produced within computer systems with less power than pi Stomp. And remember, rendered CD quality is 16-bit 44.1kHz.

Where commercial multi-effects are likely to excel, is in the quality of the individual effect software models. Each included effect has a whole team of sound professionals committed to creating near perfect models of popular classic and novel amplifiers, cabinets and effects. The current pi Stomp software uses the LV2 open standard for coding of plugin effect models. There are over 400 available LV2 plugins out there. However, like with any community developed open software, the quality can range from awesome to unusable.

To get a sense of what LV2 plugins are capable of, check out the example pedalboards with sound samples on the Listen page.

The LV2 standard is relatively new and the audience is smaller than the similar Windows/MacOS based audio plugin formats (VST, AU, AAX, etc.). Some of those plugins may be able to be ported to LV2. But there are also some companies/organizations/individuals creating some awesome native LV2 plugins, like guitarix and CALF. As the community grows, so will the quality. You can even be part of that! Create your own plugin (Build & deploy a LV2 plugin ), add it to your pi Stomp, share it with the world!

Although pi Stomp! can replace a full pedalboard, it can also be used quite well with your other pedals chained before, after or within the fx-loop. So your personal tone can still leverage the pedals that you love and then use pi Stomp to add effects that you don't otherwise own, wish consolidate or automate with presets, etc. One usecase, is to use it as a simple stomp box instead of a full pedalboard, providing less used effects (eg. pitch shifter, envelope follower, rotary speaker, etc.) as an alternative to cluttering your physical pedalboard with each of those.

Reliability, Glitching, Noise, etc.

Now we get into some geekier details. Most commercial multi-effects units are DSP based. Their processing is purpose-built to process audio in a real-time operating system (RTOS). pi Stomp! being based around Raspberry Pi and Linux, a general-purpose operating system (GPOS), is at somewhat of a disadvantage because the CPU can be busy processing tasks that a DSP doesn't have to worry itself about. The Raspbian based OS used in pi Stomp! has been optimized to eliminate or reduce many of the potential distractions that might be encountered if the Raspberry Pi was being used as a “desktop” computer, but still, buffer overruns (aka Xrun's) can be encountered when the CPU is overwhelmed and that can result in audible anomalies (eg. glitches, pops, etc.) Given the power of the Raspberry Pi 3's quad cores, Xruns are typically infrequent unless you're running a pedalboard with many plugins, greater than 8 or 10 maybe, or if quite a few of the plugins are “simulators”. The bottom line is that there's more potential for audible glitches with a GPOS based processor. A glitch here and there is usually tolerable by most recreational musicians. If you're of the more professional variety, a commercial unit might suit you better.

Digital noise is also more likely in a GPOS based system because the CPU is constantly processing requests for its many services, passing data over its various interfaces (GPIO, Wifi, etc) and radio frequency noise is just rather prevalent on development boards like Raspberry Pi. The route of digital noise into the audio path is usually via inductive coupling. Shielding and physical distance are the typical solutions applied to reduce that coupling. Experiments with shielding were done but didn't seem to reduce coupled noise by any measurable amount. Instead, I chose to keep the audio portions of the system physically sequestered to one side of the board, away from the LCD backlight and Pi as much as possible. There will be some high frequency noise noticeable when the output is sent to an amp running at high volumes. In my opinion, it's not as annoying as the noise from many gain pedals or the common 60Hz hum, but it is there and something to consider if the highest of Fi is your grail.

Performance Tests

Actual lab test results of pi-Stomp can be found here

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pi Stomp Architecture


pi Stomp has 4 main hardware modules (circuit boards):

  1. Raspberry Pi - Software host and processing
  2. Sound Card - Analog to Digital and Digital to Analog conversion
  3. LCD - User interface display
  4. Custom circuit board - Connects everything, provides interfaces for controls, MIDI, bypass, etc.

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FAQ

  • How long does it take for pi-Stomp to boot? It depends on the number of pedalboards you have. Mine with over a dozen pedalboards, takes less than 30 seconds to boot and start passing audio. Audio is passed even without power if the pedal is by bypassed. Boot time can be reduced somewhat by disabling certain services like wifi, midi, etc. Switching pedalboards takes about 1 second. Switching presets within the same pedalboard is near instantaneous, so great for switching between parts of a song.
  • How many effects/plugins can a pedalboard include? There's no hard-coded limit. The limitation is the total amount of processing required by the set of plugins. Some plugins (eg. simulators, pitch shifters, etc.) perform rather complex or numerous computations demanding more CPU than others. The MOD Web UI shows the real-time CPU demand and the number of buffer overruns. You can use these tools to assure that your constructed pedalboards won't likely exceed the available CPU resources. In practice, we've created pedalboards with over a dozen effects without issue. Some more demanding chains might need to be limited to a pedalboard with 6 or so plugins.
  • Can I buy pi Stomp as a finished product? No. That would entail many logistical issues that Tree Fall Sound is not willing to assume. Also, it's not the mission of this project. If you want a finished product, buy a Mod Duo. It's also awesome.
  • Is pi Stomp available as a kit? Not exactly. Again, the logistics of stocking a store would be beyond the scope of this project. But you should be able to purchase all the parts from just two vendors (The Parts)
  • Who is the intended audience? It's not intended for non-DIY types. It's an advanced project not intended for those new to soldering. It will take time and patience to build, to install the software and maybe even do some troubleshooting (hardware or software). Until it has been built and used by many, and the bugs are worked out, the chances of hitting a one are more likely than with a commercial device. So… It is intended for those who understand all that, and still say, “Heck, yeah, I wanna build one!” If you're a guitarist or bassist who enjoys programming/hacking, I'm pretty sure you'll enjoy all the possibilities pi Stomp provides.
  • What all is required to build/use pi Stomp? To build it, you'll need all the parts, a soldering iron with fine tip, solder, wire stripper, needle-nose pliers, diagonal cutter, tape, and small phillips/flat-head screwdrivers. “Helping Hands” or a vice will facilitate assembly. To download, install and use the software, you'll need a computer with wifi and a SD card slot (or USB SD card dongle), and a wifi router connected to the internet which supports 2.4GHz. You might need to install a free application to discover the pi Stomp IP address, and on Windows, you'll need a free SSH client (like PuTTY).
  • Will the custom hardware (circuit board & enclosure) be made Open Source? Maybe eventually. Custom circuit boards and machined enclosures are subject to lot size minimums. Tree Fall Sound has fronted the capital to purchase those in 40 piece lots so that others can build a single unit. Until TFS has recouped that capital via one-off purchases by builders, TFS will keep the designs as closed source. The store became necessary to provide the custom parts (boards & enclosures), and to reduce the number of vendors you as a builder need to deal with to just two. Without the TFS store, you'd need to source from 5+ vendors, incur shipping with each, and buy 25+ enclosures. So yeah…
  • Can I build my own hardware instead of using the pi-Stomp board? Sure. The pi-Stomp software was created to be flexible about which hardware is connected. With a few minor tweaks, you should be able to use a different LCD, soundcard, different or additional/fewer footswitches/knobs, etc.
  • Can I use software other than Modep/MOD on pi-Stomp? Yes, as long as it runs on a generic linux OS or can be compiled for the Raspberry pi architecture (armv71). You could even replace the patchbox OS completely, and replace it with another pi compatible OS. We plan to get Elk Audio OS running on it soon.
  • How can I get involved in development of pi Stomp? First, build one. If you dig it, and want to make the software better (or worse), that's awesome. The next step would be to clone the software repository at: github If you would like to discuss details, please email: support@treefallsound.com
  • Can you add feature XYZ? Maybe. Or maybe you can, see previous question. For now, please log software problems in github: Issues or feature requests in the pi-stomp forum

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Building pi Stomp


First, a word of caution. The required parts are a significant investment - about $195 (USD). It could easily turn into an expensive door stop if not soldered well. If you’ve not built a stomp box or similar piece of gear before, you might want to hone your skills a bit before attempting to build a pi Stomp.

Here is an excellent soldering guide: Adafruit Soldering Guide

You should be proficient with circuit board soldering and component identification. You’ll need a sharp/fine tip on your soldering iron, specifically, “pencil tip” - 1/32“ (.75mm) best but definitely no larger than 1/16” (1.5mm).

There are over 50 components and approximately 270 solder pads which need soldering. 120 of those are for the four 40-pin two-row connectors, with a distance of 0.1 inch between adjacent pads. If you can cleanly solder those without shorting pads or creating cold joints, you should be fine to build the rest.

If you're ready, you'll first need to buy the parts…

The Parts

It should be possible to get all parts from just two vendors: mouser.com and treefallsound.com (or Tindie).

All required parts are listed in the: Full Bill of Materials

For your convenience, the mouser.com sourced parts are stored as a BoM on their site: Mouser pi Stomp 1.0.2 BOM

If you don't need everything in the BoM, you can still add it to your mouser.com cart, then remove the specific items you don't need.

The remaining parts (circuit board, pre-drilled enclosure, footswitches, Led's, etc.) are available from: Tree Fall Sound Store. Some parts which tend to have low stock or long lead times from mouser.com may also be available there. The same bundles are also available on Tindie

Parts were chosen to be as common and available as possible. If a specific part is not available at mouser.com or treefallsound.com, check digikey.com, newark.com for general components. adafruit.com for Pi's, LCD, etc. guitarpedalparts.com for pedal specific parts. Feel free to email support@treefallsound.com for suggestions or possible access to our stock.

The Goal (in pictures)

Main Board (top)

Completed Board (top)

Completed Build (bottom)

Full Build Instructions

If you've acquired the parts and you're ready to build, go to: Full Build Instructions

Come back here when your hardware build is complete.

Warnings About Powering pi-Stomp!

Please heed these if you plan to power with anything other than the recommend power supply (listed in the BOM)

  • Although the micro USB on the Raspberry Pi can be used for powering pi Stomp (useful for hardware debugging outside of the enclosure), Do NOT connect power via power connector AND the micro USB port simultaneously. This could likely result in fire.
  • Do NOT power Pi Stomp with any power supply over 5 volts. Could possibly tolerate up to 6 volts, but certainly not 9V. For this reason, the recommended power supply (5v/2A) and power jack both have a 2.5mm center pin which prevents the likely mistake of powering pi Stomp with the 2.1mm center pin jack common on 9v pedal supplies. If you choose to use a 2.1mm center pin jack, please remind yourself and others to not use a common 9v supply.
  • If you do use a 5v supply other than the recommended, make certain the barrel connector either is center-positive or you swap the wiring from the connector to the board. Some reverse polarity circuitry exists on the Pi but some other components using the 5V rail do not. Reverse power will likely cause the magic smoke to escape the electronics and leave them non-functional.

Installing the Operating System and pi-Stomp Software

The operating system currently supported for pi-Stomp is PatchboxOS created by Blokas Labs and based on Rpi OS Lite. On top of that, you need to install the pi-stomp specific software/firmware.

You will need

  • A micro SD card. 8GB or larger. Class 10 recommended.
  • An internet connected wifi router which supports 2.4GHz (most all do, pi's don't support 5GHz though)
  • A computer with wifi and SD card slot (or USB/SD card adapter)
  • An SSH client on your computer. Mac or Linux can use a “terminal”. For windows, you can use PuTTY

Installing PatchOS onto the micro SD card

  1. Download PatchboxOS
  2. Use this guide for writing the downloaded PatchboxOS image to the SD card

Configure networking for the pi

PatchboxOS will either present an adhoc hotspot or it will try to connect to a router, not both. It initially will present the hotspot (named Patchbox). We'll use this so we can connect then configure wifi networking for connecting to your router which we'll need for downloading software.

  1. Insert the micro SD card into the disk slot at the back of the Raspberry Pi board, leave the back cover off so you can see the status LED's on the pi near the SD slot.
  2. Power it up! The red LED on the pi should immediately light. The green LED should flash indicating disk activity. If the LED's aren't lighting, turn the power off ASAP and read the Troubleshooting section.
  3. After about a minute, the green LED should be flashing less frequently. At that point, you should be able to turn-on or redirect the wifi on your computer and connect to the Patchbox hotspot named: Patchbox (password: blokaslabs)
  4. Once wifi is established, invoke your SSH client to connect to the pi:
    1. Linux/Mac Terminal: ssh patch@172.24.1.1 (password: blokaslabs)
    2. Windows PuTTY: IP: 172.24.1.1, Login: patch, Password: blokaslabs
  5. Once connected, the Patchbox wizard will come up automatically, Control-C to quit.
  6. At the command prompt, enter the following and substitute your router ID, country code and router password. Retain the double quotes. patchbox wifi connect --name “SSID” --country “CC” --password “PASSWORD”

This will restart wifi on the pi (switching from hotspot to router). Your current session will end.

Discover the IP address assigned by your router

If your pi-Stomp connected to your home router successfully, you likely won't need to know the actual IP address and you can use patchbox.local for the following steps. If you cannot ssh using patchbox.local, then come back here and try some of these discovery methods. Fing, Ping or AngryIP are recommended.

If you are not able to discover the IP, it's possible that your pi is not within range of your router, you have restrictive security settings (eg. whitelisted devices), or your patchbox wifi config info is incorrect. To try again, power cycle the pi-stomp, then repeat steps #2 through #6 above.

Install modep and pi-Stomp software

Once you know the IP, start a new SSH session:

Mac/Linux Terminal

ssh patch@YOUR-IP-ADDRESS (password: blokaslabs)

Windows PuTTY

IP Address from above, Login: patch, Password: blokaslabs

Once connected, run the following commands to download, setup and install the software and audio plugins. It could take about a half hour.

git clone https://github.com/TreeFallSound/pi-stomp.git

cd pi-stomp 

./setup.sh

If all went well, now you can reboot

sudo reboot   

First Boot, Hardware Test and Audio Setup

Hardware Test

On first boot, after a few seconds (more than 15, but hopefully less than 40), the LCD backlight should light and the system should execute a series of hardware tests, so watch the LCD and do what it says. It will ask for you to push a footswitch, turn a knob, etc. In that sense, it's also serving to familiarize you with the controls. If it receives the input it expects within 10 seconds, it'll move on to the next. If all tests pass, it will restart the pi-Stomp software and you should be good to go.

If it fails any test, there might be a wiring issue or defective part that you'll probably want to investigate. If you just want to move on despite a failed test, run the following via your ssh client:

touch ~/pi-stomp/pistomp/.hardware_tests_passed

Audio Check

  1. The leftmost Footswitch #1 should be lit indicating the pi-Stomp is processing. If it's not lit, press Footswitch #1 for a half second until the white LED is lit
  2. If you have an instrument connected to In1 and an amp connected to Out1, you should hear the audio passing thru. If not, turn up the volume.
  3. Press Footswitch #1 again until the LED goes dark. Now the pi Stomp! is bypassed. You should still hear audio passing, but it will no longer processed or affected by the Volume control.

Audio Setup (IMPORTANT!)

For optimal processing, you want the input signal to be strong enough, but not to the point of clipping. Distortion and dynamics plugins will perform less ideally if the signal is weak, and clipping just sounds like crap. When first installed, the gain is set to unity, meaning no extra gain or reduction. This might be fine for most instruments, but if your guitar has extra hot or low-output pickups, you'll want to change the gain. Here's how:

  1. Make sure processing is not bypassed. Press Footswitch #1 until it's lit.
  2. Direct a web browser to patch@patchbox.local
  3. Drag and drop a plugin named “TinyGain Mono” to your pedalboard. You'll find it under the UTILITY menu
  4. Connect it's input by dragging a purple cable from the upper left Hardware Capture 1 input to the left side of TinyGain Mono
  5. Now when you play your instrument, you should see its meter react
  6. On the pi-Stomp, long-press the top encoder knob until the System Menu appears
  7. Scroll down to the Input Gain item and click
  8. Repeatedly play your loudest chord (open E chord on guitar), and watch the TinyGain meter. It displays dB values which are negative. More negative numbers are more quiet. The goal is to get it to display a value in the negative teens, but not single digits (when the meter turns red). Use the top encoder knob to increase or reduce gain until that's the case
  9. When done, long-press the encoder knob. This value will persist between power cycles. You may need to change it when using a different instrument.

Software Updates

You should be able to use your pi-Stomp indefinitely without updates, but should you decide you require bug-fixes, new features or new starter pedalboards, the following should get you there.

In order to pull from the internet, updates can only be done when the pi-Stomp is in “router” wifi mode, not “hotspot” mode.

To switch modes:

  • Long-press the upper encoder until the System menu appears
  • Scroll to System info. Click
  • Scroll to Disable Hotspot or Enable Hotspot. Click
  • Wait for the network configuration to complete
  • Long-press to return to the main screen

Updates can currently only be done via ssh:

ssh patch@patchbox.local

pi-Stomp Software

The pi-Stomp software changes frequently and you are generally encouraged to pull new updates.

Once connected via ssh, run:

cd pi-stomp
git pull
sudo systemctl restart jack

Starter Pedalboards

To improve the out-of-box experience we will be adding starter pedalboards occasionally. These aren't meant to be spot-on, but get you in the ballpark so you can start tweaking your own tone.

Once connected via ssh, run:

cd /var/modep/pedalboards
sudo -u modep git pull
sudo systemctl restart jack

Patchbox OS

Patchbox is the base operating system created by blokas.io. It doesn't change often and unless there is a specific problem, updates are generally not necessary or recommended.

When necessary, once connected via ssh, run:

patchbox update

Troubleshooting

If you run into any hardware or software problems, first, consult the troubleshooting guide

Usage Guide


Terminology

It's important to understand the 4 P's…

Pedalboard

A pedalboard is a collection of plugins (effects, modelers, generators) and their parameter settings, routing, controller assignments, etc. Numerous pedalboards can be constructed and saved. Only one pedalboard is active at any given time.

Preset / Snapshot

A preset is a snapshot of all parameter settings for the current pedalboard. This allows for instantaneous tweaks of multiple parameters, just by changing the current preset. Each pedalboard has a “Default” preset. Others are created as needed and saved with the pedalboard. Presets are great for switching between parts of a song: Verse has light overdrive, tremolo and reverb. Chorus turns up the gain, turns off the trem, boots the mids, etc. all by hitting one footswitch (mapped to “Pre+”) or by tweaking the preset knob. The name “Snapshot” has replaced the name “Preset” from older versions of the Mod software.

Plugin

Plugins (aka Effects/Modelers/Generators) are the LV2 units (similar to VST plugins) which do the sound generation or processing and are routed together with other plugins to create a Pedalboard.

Parameter

The settings which control a Plugin.

MOD Web UI for Pedalboard Editing

Pedalboards are created and edited using a web browser via the MOD web UI. You connect to the pi Stomp over Wi-Fi. Just point a browser on your computer to patchbox.local

If you cannot connect...

You can check the wifi mode and IP address from the System menu:

  1. Long Press the “PBoard/Preset” knob until the System menu displays
  2. Scroll to System info
  3. Click

hotspot_active indicates whether pi-Stomp is available via hotspot or via router

  • “1” indicates the hotspot is active and available as Patchbox. To use it, switch your computer to that wifi network.
  • “0” indicates the hotspot is deactivated. In that case, pi-Stomp will try to connect to your router

The IP address to point your browser to is also displayed. For hotspot mode, this will likely be “172.241.1.1”. For router mode, it'll be the address space assigned by your router (eg. “192.168.1.150”)

The wifi mode can be toggled between hotspot and router modes by selecting Enable Hotspot or Disable Hotspot then clicking. It may take a few seconds to complete the connection.

Hotspot mode is generally preferred because it makes it more portable. Software download/updates require an internet connection and thus won't work in hotspot mode.

Once Connected...

You should see something like the following showing your currently active pedalboard:

For detailed usage, see the MOD User Guide: https://wiki.moddevices.com/wiki/MOD_Web_GUI_User_Guide

Saving your pedalboards writes them to the pi Stomp SD Micro drive. No computer is required from that point while accessing your pedalboard(s) from the pi Stomp.

Please note that while you are editing pedalboards, it's best to use the MOD web UI for switching pedalboards, not the knob on the pi-Stomp. If you use the knob, it's likely that the web UI will not track correctly and any saves could end up overwriting a previous pedalboard. This is a known issue with the MOD web UI when controlled via REST. Hopefully, it can be resolved in a future update.

Example Pedalboards

The pi-Stomp software setup procedure installs a set of starter pedalboards. To hear some of them in action, check out the Tree Fall SoundListen page

More examples can be found on the Mod Devices Pedalboard site. Just keep in mind that those are meant to work with the Mod Duo which includes plugins which may not be available on pi-Stomp.

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pi Stomp Hardware User Interface

The LCD shows an overview of the currently loaded Pedalboard.

  1. Pedalboard Name
  2. Preset Name
  3. Expression Pedal Assignment (plugin_name: plugin_parameter)
  4. Tweak Knob Assignment (plugin_name: plugin_parameter)
  5. Plugins in the current Pedalboard
  6. Plugin Enable (displayed bar = enabled, no bar = disabled)
  7. Footswitch Assignments - either plugins assigned to a footswitch or special functions (bypass, preset increment, preset decrement)

Two rotary encoders are used to navigate and change settings. General encoder operation:

  • Single Click - Wake up the control OR Choose highlighted selection
  • Long Press - Deep edit the selected item OR exit the current sub-screen or mode
  • Rotation - Select an item

The upper encoder is used to browse or change the current pedalboard or preset.

The lower encoder is used to make plugin changes (toggle on/off, change parameter settings, etc.)

Change the current Pedalboard

Upper encoder knob: click > click > select > click

  1. Click knob twice (until pedalboard name is hightlighted)
  2. Select a pedalboard by rotating the knob
  3. Click to activate the selected pedalboard

-

Change the current Preset

Upper encoder knob: click > select > click

  1. Click knob (until preset name is highlighted)
  2. Select a preset by rotating the knob
  3. Click to activate the selected preset

-

Enable/Disable a Plugin (Effect)

Lower encoder knob: select > click

  1. Select the effect to toggle (rotate knob until desired effect is marked with cursor)
  2. Click (each click will toggle on or off given the current state)

-

Edit Plugin (Effect) Parameters

From main screen, Lower encoder knob: select > long-press

  1. select the effect to toggle (rotate knob until desired effect is marked with cursor)
  2. long-press to enter next screen

  1. select the parameter to edit
  2. click to enter edit screen

  1. rotate knob to set desired value (value is changed in real-time)
  2. long-press to exit

Other Software

pi-Stomp is intended to be a platform. MOD is the current recommended software for audio processing and configuration, but other Linux audio software, especially if it uses Jack for audio routing, might “just work”.

Here we'll explore some possibilities: Other Software running on pi-Stomp hardware

Resources and Links

Github sources for main software used

  • mod-host plugin host software (Created by the great folks at Mod Devices)
  • mod-ui web ui (Created by Mod Devices)
  • patchbox The base OS (Created by the great folks at Blokaslabs)
  • modep The patchbox module port of Mod for Raspberry Pi (Created by Blokaslabs)

Creating LV2 Plugins

pi-Stomp in Social Media and Forums

The Future of pi Stomp!

Tree Fall Sound will continue to develop both software and hardware. Software/Firmware updates are possible without reinstalling.

Software improvements:

Hardware improvements:

  • Alternative hardware form factors (eg. simplified mono mini)
  • Color LCD
  • Improved audio (different sound card, etc.)

On top of that, all of the things the community contributes. Should be exciting.

About Tree Fall Sound


So far, we're a company of one. My name is Randall Reichenbach.

My “day jobs” have been in Electrical and Software Engineering, but my main passion has always been music. I’ve been building effects pedals and other musical gadgets since the 1980’s (read “experienced”, not “old”). I’ve always been obsessed with tone, usability and clever features. I love my (mostly analog) pedalboard, but like many musicians, I’ve long desired the ability to store awesome presets, recall them in real time, and control the effects in unique ways. As a programmer/tinkerer, I've also always wanted to be able to code (not just tweak) my own effects.

How cool would it be to create a do-everything open expandable platform, easily modifyable by anyone not too afraid of Linux, Python, etc. ? That's the idea that got me rolling on this project. Raspberry Pi and high def sound cards along with some open source software like LV2 (plugin format) and MOD/MODEP, have finally made such an endeavor possible.

I'm creating this project because I know there are others like me that would be waaay more excited playing with a piece of gear they built and can modify by getting under the hood of the hardware and software. It's been my obsession for many months and has been a blast. I spend well over 20 hours on it every week and will continue to as long as there is new functionality and features to explore. I’m hoping others will join me in this endeavor and take this platform (or their own) to places I’ve not even considered.

Some of my music can be heard at: https://soundcloud.com/user-368371534

An extensive interview and more pi-Stomp background on Blokas Reads

pi-stomp_v1.txt · Last modified: 2021/09/05 06:36 by admin