this is the monorepo for zeptocore, zeptoboard, and ectocore music devices, their documentation, their firmware, and the tools to interact with them.

for information about purchasing and documentation, visit zeptocore.com. demos are available on youtube.

The digital signal processing for all the *core things was written by Zack, from scratch, in C. This was done partially to have strict control over the sound/utility, but also because the RP2040 is fixed-point based and needed special care in all the DSP. The libraries are written with modularity in mind, so they can be used in other programs. Here are the DSP header files:

• beat repeat based on zero-crossings
• bit crush with sample rate and bit rate modulation
• comb filter tuned for some cool chaotic sounds and stereo field
• simple delay
• reverb stereo and reverb mono (stereo takes too much cpu)
• distortion/fuzz, this is a meta code file that generates the header
• reampling with linear and quadratic forms
• resonant filter which has a fade-in/out
• saturation
• shapers for a loss-type effect
• tape delay
• transfer which can also be used for wave shaping

the zeptocore device is a versatile, open-source, handmade audio player and synthesizer, featuring stereo playback of 16-bit audio files at a 44.1 kHz sampling rate.

the zeptocore supports SD-card storage for up to 32 gigabytes of samples and can recall up to 256 audio files organized into 16 banks of 16 tracks each. the zeptocore has 16 different audio effects - saturation, fuzz, delay, comb, beat repeater, filter, tape stop, reverb + more - and includes a single-cycle wavetable synthesizer. The device offers a real-time sequencer with optional quantization, optional clock sync out, and MIDI (in and out) over USB. the device has a built-in 8-ohm speaker and can be powered by two AAA batteries or USB-C.

The firmware for the zeptocore is written in C, and instructions for building the firmware are in the documentation.

the zeptoboard is the breadboard version of the zeptocore.

It retains most of the same functionality but allows you to use your keyboard and a MIDI interface (via this website) instead of the buttons on the handheld device. While this version does require some breadboarding knowledge, it is perfect for developing your ideas based on the firmware.

the ectocore is the eurorack version of the zeptocore.

this is currently under development and will be released soon. more info at https://getectocore.com/

the sample loading tool is a web-based tool (available at zeptocore.com/tool or ectocore.rocks) that allows you to load samples onto the _core devices. it is built with Go, and Vue.

the source code is located in the core folder, and information for building the tool is located can be found in the documentation.

The ectocore.rocks sample loading tool can be used offline by following the instructions for your system.

curl -L https://github.com/schollz/_core/releases/download/v6.2.13/core_macos_amd64_v6.2.13 > core_macos

curl -L https://github.com/schollz/_core/releases/download/v6.2.13/core_macos_aarch64_v6.2.13 > core_macos

chmod +x core_macos 
xattrc -c core_macos

./core_macos

Normally, ectocore and zeptocore should not freeze.

If you encounter a freeze, it would be helpful to know the following:

What SD card are you using? If you are using a custom SD card, please try using the stock SD (or approved SD card) card to see if the issue persists. If it does, please answer the following questions.

Were effects on or off during the freeze? Try turning off all effects (Break knob fully CCW) and see if the issue persists.

Are you using custom samples or the stock samples? Try using the stock samples and see if the issue persists.

Is it a particular sample that causes a freeze or any sample? If a particular sample, please provide the original sample if you can.

What was the BPM set to?

If it happens a lot, please try using this firmware which disables overclocking, allows fewer fx, but should increase the stability.

Please submit an issue with responses to these questions by clicking here or send an email to [email protected].

If, however, you want to return the device, I completely understand. Please reach out to the seller for a return.

Please note that not all SD cards are equal. Terms like "high-speed," "A1," or "U3" on the card do not necessarily indicate its actual speed performance.

Below is a list of known good and bad cards:

Do not use these cards! They may appear to work, but they can cause spurious glitches.

• Lexar brand
• Kootion brand
• Sandisk Ultra
• Kingston brand
• 5% of JUANWE cards

• Gigastone 16GB + 32GB
• SP Elite
• SanDisk Extreme
• Samsung EVO
• PNY Elite
• MicroCenter

• 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)
• MIT license for the USB library (Copyright (c) 2019 Ha Thach)