saab-93NG-bluetooth-aux

A module to augment the Aux-In functionality of SAAB 93NG's (2002/3+), to add Bluetooth media playback and steering wheel media control support.

Features

• Bluetooth music playback through the wired aux port
  • Bluetooth Auto-Reconnect feature (when entering the car, or after signal loss)
  • Play audio immediately after connecting/reconnecting to phone
  • Auto-switching to Aux input mode by reading SID data (with a help of a CAN transceiver, tested with MCP2551)
• HFP (Hands Free Profile) Audio support
  • Uses a custom Arduino ESP32 v2.0.3 core that brings in support for HFP audio
  • Switches automatically from A2DP to HFP audio when in call
  • Supports CVSD and mSBC codecs
  • I2S microphone support - tested with INMP441
• Steering wheel button controls
  • Play / Pause
  • Next / Previous
  • Voice Assistant
  • Accept incoming phone call
  • Hang up active phone call

First prototype!

Prototype parts

• ESP32 NodeMCU Board (30-pin variant)
• Adafruit I2S to Stereo DAC (UDA1334)
• MCP2515 CAN-bus to SPI interface module

Project Layout

• /saab_bluetooth_aux_kit
  • This is the PCB which all the modules will solder onto, for easy assembly.
• /esp32_a2dp_reciever
  • PIO project, the software flashed to the ESP32 module to provide bluetooth audio -> I2S functionality.
  • Also handles CAN bus messages, for steering wheel Play/Pause/Next/Previous

Notes for building your own (by jokubasver)

• INMP441 microphone pin connections to ESP32:

  • SCK - pin 16
  • WS - pin 17
  • SD - pin 21
  • L/R - GND
  • Microphone support is experimental and quite buggy.

• I-Bus connections:

  • CAN H connects to LS GMLAN1 (green wire, it can be found on the ICM connector pin 1, or solder directly to ICM connector PCB pad).
  • CAN L connects to GND
  • Connect a 4.7k resistor between CAN H and CAN L
  • If connection is unreliable, or if the ESP32 freezes - try leaving CAN L floating and disconnect the resistor.

• For Auto Aux switching, you will need to build an extra circuit:

  • 
  • This is the circuit I used on my prototype, though it's probably better to use an SN65HVD230DR connected to 3.3V instead of 5V.
  • C D Bus is the communication channel between the ICM and SID - it is UART over CAN.
  • ESP32 looks for the "AUX" string in the SID display - if Bluetooth is connected, CD button presses are sent via I-Bus until the SID displays "AUX".

• Instead of using 12V, the EHU 5V line can be used.

  • It turns off after ~10-15 seconds after locking the car with the remote.
  • 5V wakes up as soon as you unlock the car.
  • This requires the use of an isolated 5V-5V DC-DC converter (see below)

• 5V, GND, AUX Left, AUX right can be soldered on the EHU PCB. All pads are clearly marked:

• 
• 

• Using EHU 5V will cause some audible Bluetooth interference.

  • Use an isolated 5V-5V DC-DC converter to eliminate it (CC3-0505SF-E would be pin-compatible and would fit nicely on the bluetooth aux kit PCB)
  • I am personally using AM1SS-0505SJZ together with capacitors and inductors that are shown in the datasheet's example schematic.

• Warning on EHU 5V line

  • I have experienced massive current draw from the battery when using this 5V line previously, while experimenting with a generic Bluetooth Aux module. I tried it again with this project and everything is fine.
  • My guess is that my first experiment had a ground loop, and this either caused current to flow through the ground loop, draining the battery, or it confused the EHU and prevented it to go into sleep.
  • Therefore, I highly suggest you use an isolated DC-DC converter (whether you are using 12V, or 5V from the EHU)