zvukopis

an open source, DIY e-ink field recorder · a LOM project

zvukopis in a hand: the e-paper screen lists moments with their waveforms, New recording at the top

Simple mono pocket field recorder with e-ink screen

Firmware for the Waveshare ESP32-S3-ePaper-3.97 board. Open source, installed from this page in a minute.

Open source, DIY

A Waveshare e-ink board with SD card, a USB cable and a browser. MIT licence; the code is on GitHub.

96 kHz / 16-bit recording

Plain WAV files, up to 6 hours each, with embedded time of the day timecode. Microphone bandwidth to 40 kHz.

Spectrogram and FFT

Frequency analysis of any recording on the device, 0 to 48 kHz, with adjustable contrast.

Wi-Fi remote and schedule

Record from a phone, download or back everything up, and set recordings to start by themselves, even from sleep.

No notifications, no apps, no account, no feed.

In use

The side switch does everything: up or down, press in, hold in.

Record
Press in. Press again to stop. From sleep, hold the switch in and it records within seconds.
Listen
Press in on a recording. Hold up or down for tape-style varispeed, through standstill into reverse.
Mark
Hold in on a recording to tag it (sound, music, note, biophony, anthropophony, or your own words), analyse it or delete it.
Find
A calendar on the device and on the web page, by day.
Read
Markdown files in the card's doc folder open on the screen, for the quiet between recordings.
Rest
It sleeps after five minutes and wakes for a scheduled recording or a press.

Install

Loading the firmware version…

Chrome or Edge on a computer, the board on a USB cable.

  1. Connect the board, awake (if the screen says it's sleeping, hold the sleep button, marked PWR, for a second).
  2. Press Install and choose the board's port. On a new board tick Erase device; when updating, leave it unticked and recordings and settings stay.
  3. Afterwards unplug and replug the cable, or hold the sleep button for 10 seconds.
This browser can't talk to USB ports. Use Chrome or Edge on a computer. This page has to be opened over HTTPS for the browser to allow USB access.

The firmware holds no Wi-Fi credentials; the device asks for your network the first time, with a QR code on its screen. Settings on the device shows the version it runs; Settings > Firmware update shows the way back here.

More

User guide
Every screen and setting. The same file reads on the device.
Specification
The audio chain, measured levels, limits.
Releases
Each version with its notes.
Source
Firmware, this page and the tools. PlatformIO builds it.

Warning. Experimental firmware. Written by an AI (Claude) with Jonáš Gruska, tested on the device as it went, never audited. It may lose a recording, drain the battery or fail in a way nobody has seen yet. No warranty of any kind.