Skip to content

Licenses and Source Code

This Product

The X Engineering Alternator Regulator firmware and web dashboard are Copyright (C) 2026 X Engineering LLC, released under the GNU General Public License, version 3.

Complete corresponding source code for the firmware and the browser dashboard is published at github.com/markliquid1/Regulator2026-public.

Third-Party Components

The firmware incorporates the open-source components below. Each remains the property of its respective copyright holder and is used under the license shown. The license texts follow the table.

Component Copyright License
AsyncTCP (ESP32Async fork) AsyncTCP contributors LGPL-3.0
ESPAsyncWebServer (ESP32Async fork) ESPAsyncWebServer contributors LGPL-3.0
Arduino core for ESP32 Espressif Systems and contributors LGPL-2.1-or-later
ESP-IDF components (NVS, OTA, LittleFS, mDNS) Espressif Systems Apache-2.0
Mbed TLS Arm Limited and contributors Apache-2.0
ArduinoJson Copyright (c) 2014-2026 Benoit Blanchon MIT
NMEA2000 Copyright (c) 2015-2024 Timo Lappalainen, Kave Oy MIT
NMEA2000_twai (distributed here as NMEA2000_esp32_xeng) Copyright (c) 2024 Svante Karlsson MIT
INA228 Copyright (c) 2024-2026 Rob Tillaart MIT
BMP388_DEV Copyright (c) 2020 MartinL1 MIT
DallasTemperature Copyright (c) 2024 Miles Burton MIT
OneWire Copyright (c) 2007 Jim Studt and contributors; portions Copyright (c) 2000 Dallas Semiconductor Corporation MIT
Arduino PID Library Copyright (c) Brett Beauregard MIT
VeDirectFrameHandler Copyright (c) 2019 Victron Energy BV; portions Copyright (c) 2020 Chris Terwilliger MIT
ADS1115_lite Copyright (c) 2012 Adafruit Industries BSD-3-Clause
STM32duino LSM6DSOX Copyright (c) 2019 STMicroelectronics BSD-3-Clause
TinyGPSPlus Copyright (c) 2008-2013 Mikal Hart LGPL-2.1-or-later
uPlot (web dashboard) Copyright (c) 2022 Leon Sorokin MIT
esp-web-tools (documentation-site firmware installer) ESPHome contributors / Open Home Foundation Apache-2.0

Modified components

Five third-party components carry local modifications. The nature of each change is described in full in Building the Firmware:

  • AsyncTCP — one-line change in AsyncTCP.h: CONFIG_ASYNC_TCP_RUNNING_CORE changed from -1 to 0, pinning the network task to core 0. No other change.
  • Arduino PID Library (distributed here as PID_v1_xeng) — tracking anti-windup methods added; header renamed. Stock methods unchanged.
  • BMP388_DEV — I2C transaction error checking added in Device.cpp and error propagation added in BMP388_DEV.cpp.
  • VeDirectFrameHandler (distributed here as VeDirectFrameHandler_xeng) — a checksum-valid frame counter added for new-frame gating, plus corrupted-stream bounds fixes; header renamed. Stock parsing behaviour unchanged.
  • NMEA2000_twai (distributed here as NMEA2000_esp32_xeng) — transmit made unconditionally non-blocking, and a raw-receive tap hook (SetRawRxHook) added; header renamed NMEA2000_esp32.h → NMEA2000_esp32_xeng.h. The NMEA2000 library it plugs into is used unmodified.

Source for LGPL components

Source code for the LGPL-licensed components above, including the modified AsyncTCP, is available on request from joe@xengineering.net for as long as this product is supported. Unmodified upstream sources are also available from each project's own repository, linked in Building the Firmware.

License Texts

MIT License

Permission is hereby granted, free of charge, to any person obtaining a copy of this
software and associated documentation files (the "Software"), to deal in the Software
without restriction, including without limitation the rights to use, copy, modify, merge,
publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or
substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
DEALINGS IN THE SOFTWARE.

BSD 3-Clause License

Redistribution and use in source and binary forms, with or without modification, are
permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this list of
   conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice, this list of
   conditions and the following disclaimer in the documentation and/or other materials
   provided with the distribution.
3. Neither the name of the copyright holder nor the names of its contributors may be used
   to endorse or promote products derived from this software without specific prior
   written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Apache License 2.0

Full text: https://www.apache.org/licenses/LICENSE-2.0

GNU Lesser General Public License

Image Assets

The application loading-screen graphic is derived from "Sloop under full sail, close reaching, showing its fractional rig" by Stefan Ivanovich, licensed CC BY-SA 3.0, with the background removed. Per the Share-Alike term, the derived asset is likewise available under CC BY-SA 3.0.