CD changer connector
The BlueBus module uses the factory CD changer connector (13-pin round connector) to interface with your vehicle. This connector provides all necessary connections:Power connections
- Pin 1: Ground (GND)
- Pin 13: +12V switched power (Key-on power)
I-Bus connection
The I-Bus is a single-wire bidirectional communication bus used in BMW vehicles:- Pin 2: I-Bus data line
- Baud rate: 9600 bps
- Protocol: Asynchronous serial, 8E1 (8 data bits, even parity, 1 stop bit)
- Handles voltage level conversion
- Provides bus arbitration
- Protects against electrical faults
- Indicates bus status via the STATUS pin (RD0)
Audio connections
The audio connection method depends on your vehicle’s audio system configuration:- Line-level output
- S/PDIF output
- Amplified output
For vehicles with factory DSP (Digital Sound Processor):
- Pin 5: Left channel audio output
- Pin 11: Right channel audio output
- Output level: 2.1V RMS (from PCM5122 DAC)
- Signal-to-noise ratio: 113 dB
Microphone input
For hands-free telephony functionality:- Pin 6: Microphone input
- Microphone bias voltage: Configurable via settings
- Gain: Adjustable (0-15 levels)
- Pre-amplification: Software-configurable
The microphone input works with factory BMW microphones or aftermarket electret microphones. Configure the microphone bias and gain settings for optimal performance.
MCU pin assignments
The BlueBus module uses a PIC24FJ1024GA606 microcontroller. Key pin assignments:Communication interfaces
I-Bus UART (UART1)- RX: RD11 (RP12)
- TX: RD10 (RP3)
- Status: RD0
- Enable: RF1
- RX: RG6 (RP21)
- TX: RG7 (RP26)
- RX: RD2 (RP23)
- TX: RD1 (RP24)
- DTR: RD4
Bluetooth module control
BM83 Bluetooth module- Boot type: RE1
- Data select: RE4
- Multi-function button: RE5
- Reset: RF0
Audio control
I2C3 bus - For PCM5122 DAC control- SDA: RE7
- SCL: RE6
- PAM8406 shutdown: RE3
- S/PDIF reset: RE2
Telephony control
- Hardware v1
- Hardware v2
- Telephone ON: RB7
- Telephone MUTE: RE2 (shared with S/PDIF reset)
Storage and indicators
EEPROM (SPI1)- Chip select: RD8
- Clock: RP16
- Data in: RD9 (RP4)
- Data out: RP30
- On LED: RE0
- UART select: RD3 (BT=0, MCU=1)
- Board version detect: RG8 (v1=0, v2=1)
DSP configuration
If your vehicle has a factory DSP, the BlueBus can configure the input source:- Radio input: Analog input from radio (0xA1)
- S/PDIF input: Digital input from CD changer/BlueBus (0xA0)
Power requirements
- Input voltage: 12V nominal (9-16V operating range)
- Current consumption:
- Idle: ~100 mA
- Active (Bluetooth connected): ~150 mA
- Maximum (with amplifier): ~500 mA
Grounding
Proper grounding is critical for noise-free operation:- Use the ground pin on the CD changer connector
- Ensure a solid connection to vehicle chassis ground
- Keep ground paths short and direct
- Avoid ground loops by using a single ground point
Testing connections
After completing the wiring:Troubleshooting wiring issues
| Symptom | Possible cause | Solution |
|---|---|---|
| No power LED | No power or bad ground | Check pins 1 and 13, verify voltage |
| Module powers on but not detected | I-Bus connection issue | Verify pin 2 connection, check TH3122 status |
| No audio output | Wrong audio mode or bad connection | Check DSP input source setting, verify audio pins |
| Poor audio quality | Ground loop or interference | Improve grounding, check cable routing |
| Microphone not working | Bias voltage or gain issue | Adjust microphone settings in configuration |
Next steps
Once wiring is complete:- Configure your display unit settings
- Pair Bluetooth devices
- Adjust audio settings
- Configure telephony settings if using hands-free