An open-source ESP32-WROOM-32 development board by halfmarble, designed in KiCad. NEAToBOARD breaks the ESP32 out onto a breadboard-friendly board with USB, on-board programming, a battery power path, and a built-in set of I/O for learning and prototyping.
- ESP32-WROOM-32 module
- USB micro-B with a CH340C USB-to-UART bridge and the standard auto-reset / auto-bootloader circuit (no need to press buttons to flash)
- Reset and two general-purpose push buttons
- Battery support — JST-PH VBAT input with a Schottky power-path and a voltage divider for battery sensing, plus a 500 mA resettable fuse
- 32.768 kHz crystal for the RTC / deep-sleep timekeeping
- On-board I/O for experimentation: a 5×4 LED matrix, RGB LED (WS2812B), and discrete feedback LEDs
- I²C header plus a Qwiic connector, and an SPI header
- JTAG header for debugging
- M2 mounting holes; panelized with mouse-bite tabs
See the full schematic (PDF) and the pinout diagram.
hardware/
KiCad-project/ KiCad 7 project — open NEAToBOARD_ESP32.kicad_pro
NEAToBOARD_ESP32.kicad_sch main schematic
NEAToBOARD_ESP32Extras.kicad_sch sub-sheet
NEAToBOARD_ESP32.kicad_pcb board layout
HalfMarble.pretty/ project footprint library
HalfMarble.3dshapes/ project 3D models (.step/.wrl) and symbols
board2pdf.config.ini board2pdf plugin config (fabrication PDFs)
ibom.config.ini InteractiveHtmlBom plugin config
bom/ rendered interactive BOM (bom.html)
pinout/ pinout artwork source (pinout.pxd)
3d/
NEAToBOARD-ESP32.stl 3D-printable model of the board
docs/ rendered schematic PDF and pinout image
BOM.csv bill of materials (values, footprints, manufacturer part numbers)
The authoritative source of truth is the KiCad schematic — BOM.csv is a convenience export so you can read the parts list without opening KiCad.
Open hardware/KiCad-project/NEAToBOARD_ESP32.kicad_pro in KiCad 7 (the files are saved in the 20221018 format). The custom footprint and 3D-model libraries are bundled inside the project and referenced with ${KIPRJMOD}, so they load automatically — no global library setup required.
There is no firmware in this repository — NEAToBOARD runs any ESP32 firmware. Flash it with your toolchain of choice (Arduino core for ESP32, ESP-IDF, MicroPython, etc.) over the USB port; the on-board auto-reset/auto-bootloader circuit handles entering download mode, so no button presses are needed.
The pin layout is based on the DFRobot FireBeetle ESP32 (with parts of Adafruit's ESP32 board). The simplest path is to target the FireBeetle ESP32 board definition / pin map — most pins line up. If you select a different board definition, expect to re-map a few GPIO assignments to match this board; cross-check against the pinout diagram and the schematic.
docs/defensive-publication/ contains a defensive
publication — Synchronized Multi-Line Digital Signal Generation Using Plural Independent
Software-Triggered Serializer Peripherals With Open-Loop Fixed Start-Skew Compensation —
published in the Technical Disclosure Commons, Defensive Publications Series
(www.tdcommons.org/dpubs_series/10442), an
examiner-searched prior-art database, together with
load-bearing source excerpts. It documents, as dated public prior art, a technique for
synthesizing a USB full-speed D−/D+ differential signal on an ESP32 (a board like this
one) by driving two independent SPI controllers in lock-step: a CPU-fenced back-to-back
start makes the inter-unit skew deterministic, and a fixed configured MOSI delay cancels
it open-loop. It is published defensively to keep the technique freely practicable by all.
The hardware design — schematic, PCB layout, footprint and 3D-model libraries, and the rest of the design files in this repository — is licensed under the CERN Open Hardware Licence Version 2 – Permissive (CERN-OHL-P-2.0). See LICENSE for the full text. The defensive-publication document under docs/defensive-publication/ is licensed CC-BY-4.0, and the source excerpts therein retain their original Apache-2.0 headers.
Copyright halfmarble 2023.
This source describes Open Hardware and is licensed under the CERN-OHL-P v2. You may redistribute and modify this documentation and make products using it under the terms of the CERN-OHL-P v2 (https://ohwr.org/cern_ohl_p_v2.txt). This documentation is distributed WITHOUT ANY EXPRESS OR IMPLIED WARRANTY, INCLUDING OF MERCHANTABILITY, SATISFACTORY QUALITY AND FITNESS FOR A PARTICULAR PURPOSE. Please see the CERN-OHL-P v2 for applicable conditions.
The pin layout and parts of the design are based on the DFRobot FireBeetle ESP32 and Adafruit's ESP32 board — both open-hardware designs. Thanks to those communities.