Effects Pedal Simulator Raspberry PI with Pisound

This is brand new alpha software.

Pisound provides the digital signal processing and the Raspberry Pi runs LV2 effects. A USB foot pedal switches between digital effects.

The USB foot pedal is essentially a USB keyboard with only a few keys.

MODEP

MODEP is a front end for LV2. It facilitates setting chains of effects with an intuitive web app front end.

Installation

On a Raspberry PI with modep, modep-mod-ui, and all the associated LV2 plugins
Install mod-host in /home/patch and build using make PREFIX=/home/patch/mod-host and make PREFIX=/home/patch/mod-host install
Clone this repository into /home/patch
Compile driver: make zip in /home/patch/ModHostPedal
Set up some pedals (see Configuring the Pedal below)
Run ./EffectsStart in /home/patch/ModHostPedal

Setup

Using https://blokas.io/modep/ set up some pedal boards and save them into the library

In a terminal switch to the ModHostPedal directory

Run ./EffectsStart as root

To restore Modep/mod-host run ./EffectsStop as root

Configuring the Pedal

The pedal is a USB keyboard with three keys. 'A', 'B', and 'C'

They load instructions from the files in PEDALS

Put a link in PEDALS from 'A' -> WhateverPedalFile and the left most pedal will trigger loading that pedal

Control

The script EffectsStart stops the Modep/mod-host process and starts this pedal's process. EffectsStop stops the software for this pedal and restarts the Modep/mod-host process

The scripts setpedals03.sh and setpedals04.sh are example scripts for changing the pedal board. They must be run as root (to access the led on the Pisound. Otherwise they could be run as the patch user)

How Fast?

A design goal is sub 10,000 micro seconds, one hundredth. This has not nearly been achieved.

Using data the driver writes into /tmp/driver.log the following averages

grep Implemen /tmp/driver.log |cut -d ' ' -f 2-3|sort |perl -e 'while(<>){/^(..)\s+(\d+)\s*$/ or die $_; defined $cnt{$1} or $cnt{$1} = 0; $cnt{$1}++; defined $reg{$1} or $reg{$1} = 0; $reg{$1} += $2; } print join("\n", map{"$_ => " . ($reg{$_}/$cnt{$_})} sort keys %reg)."\n";'

A: => 63489.3333333333
B: => 51726.6666666667
C: => 82500.1666666667

Ridiculously precise! And there is quite a bit of variation.