Imported from GitHub: halleysfifthinc/AVCLAN-Mockingboard · commit 8141bd3 · license GPL-3.0

Description

Emulate a CD Changer on a Toyota AVC LAN network

README

AVCLAN Mockingboard

This project adds an aux in to the stock head unit of compatible Toyota vehicles by emulating an external CD changer. The Mockingboard communicates with the head unit over the AVC-LAN bus, Toyota's name for their messaging protocol over the NEC (now Renesas) IEBus. Also included is a Wireshark dissector for IEBus and AVC-LAN. AVC-LAN is sparsely documented publicly; this dissector collects what's known from prior art alongside my own findings.

Features:

• Select/switch between internal CD player and mockingboard by pressing the "CD" button (repeated presses toggle between internal and external CD players)
• Generally complete handling of physical interface (track next/prev, fast-forward/rewind, track/disk repeat and random; "scan" button and change disc buttons are currently unimplemented for lack of use/purpose)
• Play/pause, next/prev control of connected phones via headset functions (mimicing the button press on a wired headset; requires phone support and connection using a TRRS aux cable)

Future plans (Mockingboard v2)

• Bluetooth functionality
  • "Scan" button repurposed to enter bluetooth pairing mode
  • Button actions (play/pause, track skip, ff/rw, [disc] repeat/shuffle) mapped to AVRCP
  • Song info/status (time, etc) relayed to head-unit (i.e. time display matches actual song/audio time)
• Redesign hardware based on RPi Pico 2W (RP2350 + Bluetooth)
  • PIO used to implement:
    • AVCLAN comms
    • I2S audio
  • Dual audio input options (aux in, bluetooth)
    • Switched audio jack to sense aux plug presence
  • Audio codec with differential output (better rejection of electrical noise, e.g. from adjacent AVCLAN bus lines)
  • Switching regulator (easier assembly)
  • CAN transceiver
    • TX/RX connected to different diodes (or different pads of a single dual/multicolor LED package) for observability

Helpful links/prior art:

• IEBus/AVCLAN decoder and message dumps (inc. a CD changer) for Sigrok
  • https://github.com/sigrokproject/sigrok-test/pull/22
  • https://github.com/sigrokproject/sigrok-dumps/pull/43
  • https://github.com/sigrokproject/libsigrokdecode/pull/106
• https://web.archive.org/web/20230319000356/http://softservice.com.pl/corolla/avc/avclan.php
• https://web.archive.org/web/20040617005106/http://www.interfacebus.com/Design_Connector_IEbus.html
• https://web.archive.org/web/2/https://old.pinouts.ru/Car-Stereo-Toyota-Lexus/Toyota_1990-2002_CD_Chang_pinout.shtml
• https://web.archive.org/web/20240519043021/https://pop.fsck.pl/hardware/toyota-corolla.html
• https://github.com/GadgetNutt/AVC-LAN-Module-Builder

Hardware

I ordered the boards partially assembled from JLCPCB (to keep costs down, I ordered and soldered some non-standard/stocked parts myself.)

The non-populated/assembled BOM is:

Mouser #:	Mfr. #:	Desc.:	Order Qty.	Unit Price (USD)
579-ATTINY3216-SNR	ATTINY3216-SNR	8-bit Microcontrollers - MCU 8-bit Microcontrollers - MCU 20MHz, 32KB, SOIC20, Ind 105C, Green, T&R	1	$1.27
523-L717SDE09PA4CH4	L717SDE09PA4CH4F	D-Sub Standard Connectors D-Sub Standard Connectors D SUB R/A	1	$1.98
490-SJ-43514	SJ-43514	Phone Connectors Phone Connectors audio jack, 3.5 mm, rt, 4 conductor, through hole, 0 switches	1	$1.35
667-ERZ-V20D220	ERZ-V20D220	Varistors Varistors 22V 2000A ZNR SUR ABSORBER 20MM	1	$1.24
538-22-28-8093	22-28-8093	Headers & Wire Housings Headers & Wire Housings 2.54MM BREAKAWAY RA 9 CKT Gold	2	$0.76
865-XC6701D502JR-G	XC6701D502JR-G	LDO Voltage Regulators LDO Voltage Regulators 28V High Speed Voltage Regulator	1	$1.36
563-EXN-23350-BK	EXN-23350-BK	Enclosures, Boxes, & Cases Enclosures, Boxes, & Cases Extruded Aluminum Enclosure Black (1.4 X 2.7 X 1.9 In)	1	$14.40

An earlier version of the board* lacked cutouts in the corners to fit the ends of the intended housing, so I haven't used the listed enclosure (yet).

*Only version of the board I have ordered so far.

Cable harness

I ordered a cable harness from Amazon to acquire the head-unit side connector. I then cut the male end off a DB9 cable and connected the wires according to the following cable harness diagram:

Firmware

Building

With VS Code:

1. Install VS Code and Docker
   • Required extensions: Dev Containers
2. Open repo in VS code and wait for notification asking to re-open in dev container.
   • Wait for container to build and extensions to install
3. Select CMake build configuration
4. Start developing!

Natively/without VS Code Dev Containers

1. Install avr-gcc >= v13.1, binutils >= v2.39, cmake >= v3.24
2. Configure cmake in repo with cmake -B build
   • Trigger builds with cmake --build build
3. Start developing!

Flashing

The CMake target upload_mockingboard uses the AVRDude utility using the "serialupdi" programmer type. I use a USB => Serial converter with the Rx and Tx lines connected, using one of the options described by SpenceKonde here.

Protocol reverse-engineering

The "scripts/packet-analysis" folder contains a Wireshark Lua plugin that defines a dissector for IEBUS and AVC-LAN messages.

License

The firmware for this project is licensed under the GNU GPLv3, and the hardware is licensed under the Solderpad Hardware License v2.1, a wraparound license to the Apache License 2.0.