Introduction

Thermoquad is an open source ecosystem for Chinese diesel heaters. Think of it like the open source parts of Android, but for heating systems.

Chinese diesel heaters are affordable and widely available, but their stock control systems are limited, proprietary, and often incompatible between manufacturers. Thermoquad provides open hardware designs, open firmware, and open protocols that anyone can use, modify, and improve.

The ecosystem includes firmware for ignition control and thermostat management, hardware designs for controllers and interfaces, and software for monitoring and integration. All components communicate using the Fusain protocol, an open serial communication standard designed for reliability.

Who is Thermoquad For?

Thermoquad is designed to serve four distinct groups of users:

Tuners & Experimenters

For those who want to push their heater beyond stock capabilities—adjusting fuel/air ratios for cleaner burns, extending temperature ranges, fine-tuning startup sequences, or experimenting with different fuel types. Thermoquad provides full control over every parameter with real-time telemetry.

Your setup: Replace your stock control board with Hades running Helios. Add a Block for wireless connectivity. Use Roastee on your laptop to monitor live telemetry, adjust parameters, and log data while you experiment.

Users Who Want a Better Experience

For those who just want their heater to work well. Stock controllers are clunky, displays are hard to read, and voice prompts with strange accents are annoying. Thermoquad provides clear temperature displays, intuitive operation, and quiet, unobtrusive feedback.

Your setup: Keep your existing heater and wiring. Add a Block that connects via LIN using your stock cables. Control everything with Luna’s simple 3-button OLED interface—perfect for adjusting temperature from your sleeping bag. Or use Roastee on your phone when you want more detail.

Repairers & DIYers

For those whose ICU died and can’t find a compatible replacement, or whose controller stopped talking to their heater. Thermoquad solves the compatibility nightmare with one ICU design that works with common heater hardware, open documentation for diagnosing problems, standard connectors and pinouts, and detailed logs for maintenance tracking.

Your setup: Replace your dead stock board with Hades. Pair it with a Block and you’re back in business—no hunting for obscure replacement parts. Use Roastee to check runtime hours, error history, and maintenance intervals.

Integrators & Builders

For those building something bigger—a van, boat, workshop, or off-grid cabin—who need multiple heaters working together, integration with automation systems, custom damper and zone control, and remote monitoring. The open Fusain protocol makes integration straightforward.

Your setup: Install Hades boards in each heater, connected via RS-485 to a central Block. Use Roastee or Home Assistant to orchestrate zone temperatures, schedules, and coordinated operation. Wall-mount a Luna for quick manual control. Roastee connects over WiFi for remote monitoring.

Project Components

Firmware

Helios

The Ignition Control Unit firmware—the brain that controls your heater. Runs on Hades hardware, or a Raspberry Pi Pico 2 for prototyping.

Slate

The thermostat and control hub firmware. Manages temperature regulation and serves as the integration point for automation systems. Runs on Block and Luna hardware, or a Raspberry Pi Pico 2 for prototyping.

Hardware

All Thermoquad hardware is based on the RP2350.

Hades

The ICU board that runs Helios. Connects to heater components and replaces the stock control board.

Block (working name)

A wireless bridge that runs Slate. Features LIN for retrofitting heaters using stock wiring, RS-485 for new builds or customized rebuilds, WiFi and Bluetooth for user connectivity, and 4 RGB status LEDs. Designed to be IP68 compliant.

Luna

A handheld interface with an OLED display and 3 buttons. Battery powered and IP68 compliant, designed to be easy to use in dark settings like a tent. Can also be wall mounted in hardwired installations, requiring only power (5V–36V). Connects wirelessly to a Block.

Software

Roastee

A progressive web app for desktops and phones. Connects to Blocks and Lunas via WiFi or Bluetooth for remote monitoring and control.

Heliostat

A development tool for monitoring and debugging the Fusain protocol.

Protocol

Fusain

The communication protocol that ties everything together. Open, documented, and designed for extensibility. See Overview.

Project Goals

Open

All designs, firmware, and protocols are open source. Use them, modify them, share them.

Compatible

Work with existing heater hardware. You shouldn’t need to buy a new heater or run new wires to use Thermoquad.

Documented

Good documentation is as important as good code. If it’s not documented, it doesn’t exist.

Getting Started

• Getting Started — Set up your development environment

• Helios ICU — Learn about the Helios ICU firmware

• Overview — Understand the communication protocol

• Hardware — Hardware specifications and pinouts