AV Control Unit
Introduction
This is a computer running Windows CE / Windows Automotive. It runs software from its internal memory and from an SD card which is required for operation.
While referred to as the AV Control Unit in service manuals, other names are commonly used:
- Head unit
- Radio
- In-Vehicle Infotainment (IVI) unit
- Navigation unit
Model numbers
Gen 1
Clarion QY7204, QY7224, QY7214, QY7254
Gen 2
(information needed)
Photos
Functions
Connections
- It communicates with various systems in the car via CANBUS
- It connects to the Telematics Control Unit (TCU) via USB and CANBUS
- It receives a video signal from the Around View Monitor Control Unit, and also controls it via CANBUS
SD card
The SD card contains map data in a user-accessible partition, part of the firmware (Windows CE image) in unpartitioned space near the start of the SD card, and a hidden partition towards the end containing the substance.skn file which contains icons and strings.[1]
In Gen 1 units, the SD card is locked. The password can be captured by dumping the flash memory of the unit, or by intercepting the communication to the SD card itself during boot.
In Gen 2 units, the SD card is not locked, as in its contents can be freely read and written.
An SD card can also be used to update the firmware in the unit.
Debugging
Gen 1 units (not sure about Gen 2) have a UART exposed on the 40-pin connector, which provides a debug shell.[1]