8Pto8U Translator

Zephyr firmware for an STM32 Nucleo-C542RC that helps an Audi A3 8P work with an Audi 8U Q3 instrument cluster.

This firmware does two jobs on 100 kbit/s comfort CAN:

• Translates A3 8P wiper stalk MFD/DIS controls into 8U Q3 cluster MFD/DIS controls.
• Transmits the A3 comfort can status heartbeat needed for window and sunroof operation with the 8U cluster installed.

Hardware

• STM32 Nucleo-C542RC
• 5V Buck Converter

Installation

Connect STM32 CanH/CANL at CANBUS Gateway (J533) on Comfort CAN.

Connect fused 12v Power to 5v Buck Converter to Terminal 15 (ign) power source, then 5v buck converter to the STM32.

Stable Firmware to Flash to the STM32 is located on the releases page.

CAN Behavior

Translation starts enabled at boot. Live sniff logging starts disabled so serial printing does not add unnecessary load while driving the cluster.

Stalk To Cluster

A3 8P stalk input	8U Q3 cluster output
0x5C1 22000001 short up press	0x5BF 06000111 up
0x5C1 23000001 short down press	0x5BF 06000F11 down
0x5C1 28000001 short OK press	0x5BF 07000111 OK
0x5C1 22000001 held up press	0x5BF 03000111 left
0x5C1 23000001 held down press	0x5BF 02000111 right
0x5C1 28000001 held OK press	0x5BF 01000111 menu

Each translated cluster command is followed by release:

0x5BF 00000011

Comfort Heartbeat

The firmware transmits this frame every 500 ms:

0x551 03

This fixes A3 8P window and sunroof operation (and other comfort can operations) when the 8U Q3 cluster is installed.

Serial Commands

Connect to the ST-LINK virtual serial port at 115200 baud.

Command	Meaning
stats	Print bitrate, counters, CAN state, and error counters
sniff on	Enable live CAN frame printing
sniff off	Disable live CAN frame printing
translate on	Enable stalk-to-cluster translation
translate off	Disable stalk-to-cluster translation
send <id> <data>	Send a standard classic CAN frame

Example:

send 5BF 07000111

Build

This project expects a Zephyr workspace and Python virtual environment beside the exported source tree:

.
├── .venv/
├── can_sniff_inject/
├── scripts/
└── zephyr-workspace/

Build for the Nucleo-C542RC:

scripts/build-stm32.sh

The build output is written to:

build/can_sniff_inject/zephyr/

Flash

Flash with pyOCD:

.venv/bin/pyocd flash -t STM32C542RCT6 build/can_sniff_inject/zephyr/zephyr.hex

Or copy the generated binary to the ST-LINK mass-storage volume:

scripts/flash-stm32-mass-storage.sh

Monitor

scripts/list-stm32-ports.sh
scripts/monitor-stm32.sh