The controller
A small, protected ESP32-C6 board with two CAN interfaces, built from automotive-grade parts. The whole design is open source.
The board
- ESP32-C6 Mini with built-in Wi-Fi for the configuration interface.
- Two independent CAN (TWAI) interfaces: one for the car, one for the Haldex.
- Protected power supply with a built-in fuse and protection against ESD and voltage transients.
- RGB status LED that shows the active mode, with adjustable brightness.
- Mode button on the board, plus a 12 V input for an external switch.
- Two high-side outputs for brake and handbrake signals on Gen1 and Gen2, or for other jobs such as PWM oil-cooler control.
- USB-C for firmware updates and SavvyCAN over serial.
The C6 replaces the earlier Teensy-based OpenHaldex T4, adding wireless configuration and on-device setup.
Connector pinout (MX23A12NF)
| Pin | Signal | Notes |
|---|---|---|
| 1 | Vbatt | +12 V permanent |
| 2 | Ground | Ground |
| 3 | Chassis CAN low | To car side |
| 4 | Chassis CAN high | To car side |
| 5 | Haldex CAN low | To Haldex coupling |
| 6 | Haldex CAN high | To Haldex coupling |
| 7 | External mode switch | +12 V to activate |
| 8 | Brake switch in | +12 V input |
| 9 | Brake switch out | Gen1 and Gen2 only |
| 10 | Handbrake switch in | +12 V input |
| 11 | Handbrake switch out | Gen1 only |
Some platforms need a 10k pull-down resistor on the brake or handbrake outputs.
Build your own
Schematics, PCB layouts, Gerbers, the bill of materials and the 3D-printable enclosure are all in the OpenHaldex-C6 repository under the MIT License. Order boards from any PCB house, flash the firmware with the updater, and you're done. The pinout and functions stay the same across enclosure versions.
If you'd rather not, Forbes Automotive sells controllers assembled, tested and ready to fit.
OpenHaldex C6 FD In development
The next controller adds CAN FD, which newer drivetrains use in place of classic CAN. That's what opens the door to Generation 6 Haldex and Magma differentials. The C6 FD will sit alongside the C6 rather than replace it.
Planned for the C6 FD:
- CAN FD support for Gen6 and Magma differentials
- An external driver for PWM pump control
- An LED output for a dashboard mode display
- A rotary switch input to select modes directly