schollz / _core

firmware for the zeptocore, zeptoboard, and ectocore

_core

this is the source code for _core music devices that utilize the rp2040. devices may differ, but the basic specification is as follows:

• mono or stereo playback of 16-bit (internal 32-bit) audio files @ 44.1 kHz sampling rate
• sd-card storage for audio + data
• recall up to 256 audio files (16 banks of 16 tracks)
• digital low-pass and high-pass filter
• basic single-cycle wavetable synthesizer
• realtime sequencer with optional quantization
• low-latency (<10 ms)

there are a few versions of the "_core" devices that utilize this firmware:

boardcore

breadboard version (see demo).

• WeAct Raspberry Pi Pico (others should work too) ($2.50)
• pcm5102 ($9)
• sdio sd card ($3.50)

zeptocore

hand-held version (see demo).

goals

the goal of this project is to produce a device that achieves compelling music without learning, though learning is rewarded.

non-goals

a non-goal for this project is to be emulate a specific musical device.

a non-goal for this project is audio synthesis. though I may change my mind about this.

similar devices

if you like this device, you might also like:

• joydrums, as if a beat pad and a loop pedal had a baby.
• bitty, an Arduino-compatible device that makes making music fun.
• hss2020, a trimmed down version of the hard soft synth that fits in the hands.
• phantasmal force, a micro midi controller.

zeptocore spec (draft)

knobs: X, Y, Z

top buttons are A, B, C, and D.

the rest of the buttons (1-16) are just called H.

combo buttons

• H + H → JUMP: retrig depending on location
• A + H → JUMP: do fx (toggle), MASH/BASS: do jump
• A + B → JUMP mode
• A + B + B ... → set tempo via tapping
• A + C → MASH mode
• A + D → BASS mode
• B → show bank (blinking) + sample (bright)
• B + H + H → select bank (1st) + sample (2nd)
• B + C → start/stop
• B + D → mute
• C → display which sequence is selected (bright)
• C + H → select sequence (led dim or bright = used, led off or blinking = unused)
• C + H + H + H ... → chains sequences together, though the first selected must be empty
• C + B → toggle play sequence
• C + D → toggle record sequence
• C + D, C + D → erase current sequence
• D → shows current slot (blinking / bright) and slots with data (dim)
• D + H → select save slot
• D + B load from save slot
• D + C → save into save slot

combo knobs

• A + X → tempo
• A + Y →
• A + Z → volume
• B + X →
• B + Y → filter fc (lowpass/highpass?)
• B + Z →
• C + X → pitch
• C + Y →
• C + Z → quantize
• D + X →
• D + Y →
• D + Z →
• [o] H + X/Y/Z -> in MASH mode this edits the parameters of the effect

effects

there are 16 effects in four categories - "shape", "time", "space", and "pitch". holding an effect and using a knob will change its parameters.

• 1 -> warm (preamp postamp)
• 2 -> loss (type+threshold, postamp)
• 3 -> fuzz (preamp postamp)
• 4 -> crush (frequency, bitdepth)
• 5 -> reverse
• 6 -> stretch
• 7 -> delay (delay feedback, delay length)
• 8 -> repeat (repeat length)
• 9 -> tighten (gate amount)
• 10 -> heighten (tremelo speed, depth)
• 11 -> circulate (pan speed, depth)
• 12 -> scratch (scratch speed)
• 13 -> lower (depth)
• 14 -> slower (duration, depth)
• 15 -> faster (duration, depth)
• 16 -> stop (duration)

cheat codes

• 1,2,1 -> toggle variable splice playback
• 4,5,4 -> toggle one-shot mode
• 6,7,6 -> toggle play mode
• 5, 8, 7, 6 -> toggle tempo match mode
• 9,12,10,11 -> change resampling (linear or quadratic)
• ?? -> toggle sync mode?

needs

• pitch
• gate
• all probabilities
• distortion level
• distortion wet
• saturation wet
• probability jump
• probability reverse
• probability retrig
• probability tunnel
• probability repitch

building image

windows

Install WSL 2

$ wsl --set-default-version 2
$ wsl --install Ubuntu

Then restart computer and run

$ wsl --install

That should start your system. Then you can follow the Linux directions:

linux

Install the pre-requisites:

sudo apt install cmake gcc-arm-none-eabi libnewlib-arm-none-eabi libstdc++-arm-none-eabi-newlib git python3 g++
sudo -H python3 -m pip install numpy matplotlib tqdm icecream librosa click

Clone this repo and install the Pico SDK:

git clone https://github.com/schollz/_core
cd _core
git clone https://github.com/raspberrypi/pico-sdk
cd pico-sdk &&  git submodule update --init

Do a build:

make clean zeptocore

(replace 'zeptocore' with 'ectocore' if you are building the latter)

building upload tool

windows

First install Scoop, open PowerShell terminal and type:

> Set-ExecutionPolicy -ExecutionPolicy RemoteSigned -Scope CurrentUser
> Invoke-RestMethod -Uri https://get.scoop.sh | Invoke-Expression

Then in the Powershell:

> scoop update
> scoop install go zig sox

Now you can build with:

> cd core
> $env:CGO_ENABLED=1; $env:CC="zig cc"; go build -v -x

Now the upload tool can be run by typing

./core.exe

license

• Apache License 2.0 for no-OS-FatFS (Copyright 2021 Carl John Kugler III)
• MIT license for the SdFat library (Copyright (c) 2011-2022 Bill Greiman)