MIB2-Can-Bridge - MK5/MK6/B6/B7/NMS

MIB2 / RCD330 CAN Bridge

Latest firmware located on RELEASES page.

For Vehicles with RED MFD. (Time Fix Available for B&W MFD)

Gateway Upgrade still required for proper Infotainment Function.

Flash using Teensy Loader.

A Teensy 4.0 dual-CAN bridge for fixing the Screen Brightness, MFD Display, and Track/Station Seek on the Steering Wheel.

The bridge sits inline between the car and the radio. Most CAN traffic is forwarded transparently. The firmware only modifies or consumes the specific frames needed for the supported features.

Features

Implemented

• Fixes MIB2/RCD330 screen brightness on cars by correcting the illumination/dimming message. (MIB2 STD/Nav & RCD330)
• Keeps the radio responsive to the dash dimmer wheel when ambient/headlight illumination is active. (MIB2 STD/Nav & RCD330)
• Translates MIB2/RCD330 audio text to the Red MFD Audio page. (MIB2 STD/Nav)
• Translates MIB2 navigation distance/street text to the Red MFD Navigation page. (MIB2 Nav only)
• Navigation Route Maneuver Arrows on Red MFD Nav Page (MIB2 Nav only)
• Optionally maps steering wheel MFD Up & Down buttons to previous/next while the Audio page is actively displayed. (MIB2 STD/Nav only)
• MK6/B7/NMS B&W MFD Cluster Time Sync Fix (MIB2 STD/Nav only)

VCDS/OBD11 Coding Needed

For Brightness fix to work correctly:

MIB2: 5F Infotainment Control Unit --> Adaptations --> Dimming illumination for Display Unit --> Y3 to 35% and Y4 to 100% Security Access code may be needed: 20103

RCD 330 (May not be available on all RCD330s): 56 Radio Control Unit --> Adaptations --> Dimming illumination for Display Unit --> Y3 to 35% and Y4 to 100% Security Access code may be needed: 20103

Hardware Needed

Qty	Part	Notes
1	CANBus Gateway	Gateway Upgrade needed for Proper communication and sleep. 7N0907530BC or Similar.
1	Teensy 4.0	Main controller.
2	3.3 V CAN transceiver modules	SN65HVD230 modules work well. Use boards with TXD, RXD, VCC\3.3, GND, CANH, and CANL.
1	12 V to 5 V automotive buck converter	Use a high quality converter with stable output.
1 (Optional)	VW quadlock extension or breakout harness	Strongly preferred so the car loom does not need to be cut.
1	2A Inline fuse	Put this on the adapter power feed.
As needed	Twisted pair wire in Recommended Colors	Use for both CANH/CANL connections.
As needed	Solid Core wire in Recommended Colors	Use for all other connections.
As needed	Heat shrink, solder, crimp terminals, solder sleeves, strain relief	Build it like it will live in a dashboard, because it will.

Recommended wire colors:

Signal	Suggested color
CAN High	Yellow
CAN Low	Green
12 V / 5 V / 3.3 V Positive (+)	Red
Ground (-)	Black
TX	White
RX	Blue

Avoid:

• 5 V-only CAN transceiver boards

Wiring Overview

The module is an inline bridge. The car CAN wires go into one transceiver, the radio CAN wires go into the other transceiver, and the Teensy forwards traffic between them.

flowchart LR
    car["Vehicle side harness"] --> bridge["Teensy 4.0 CAN bridge"]
    bridge --> radio["MIB2 / RCD330 radio"]
    power["12 V accessory / radio power"] --> buck["12 V to 5 V buck converter"]
    buck --> bridge
    ground["Vehicle ground"] --> bridge

Loading

Detailed CAN Layout

flowchart LR
    subgraph Vehicle["Vehicle side"]
      VCH["Vehicle CAN-H"]
      VCL["Vehicle CAN-L"]
    end

    subgraph Bridge["Bridge module"]
      TA["Transceiver A\nvehicle side"]
      T40["Teensy 4.0"]
      TB["Transceiver B\nradio side"]
    end

    subgraph Radio["Radio side"]
      RCH["Radio CAN-H"]
      RCL["Radio CAN-L"]
    end

    VCH --> TA
    VCL --> TA
    TA --> T40
    T40 --> TB
    TB --> RCH
    TB --> RCL

Loading

Point-To-Point Wiring

Power

From	To
Vehicle switched/accessory 12 V	Buck converter input positive
Vehicle ground	Buck converter input negative
Buck converter 5 V output	Teensy VIN
Buck converter ground	Teensy GND
Teensy GND	Both transceiver GND pins
Teensy 3.3V	Both transceiver VCC/3.3 pins, if using 3.3 V transceiver modules

Set and verify the buck converter output before connecting the Teensy. The Teensy wants 5 V on VIN, not raw vehicle voltage.

Vehicle-Side Transceiver A

Signal	Teensy 4.0 pin / label	Transceiver A pin
CAN1 TX	CTX1, pin 22	TXD
CAN1 RX	CRX1, pin 23	RXD
3.3 V	3.3V	VCC/3.3
Ground	GND	GND
Vehicle CAN High	vehicle side harness CAN-H	CANH
Vehicle CAN Low	vehicle side harness CAN-L	CANL

Radio-Side Transceiver B

Signal	Teensy 4.0 pin / label	Transceiver B pin
CAN2 TX	CTX2, pin 1	TXD
CAN2 RX	CRX2, pin 0	RXD
3.3 V	3.3V	VCC/3.3
Ground	GND	GND
Radio CAN High	radio side harness CAN-H	CANH
Radio CAN Low	radio side harness CAN-L	CANL

Notes:

• TXD/RXD are logic signals between the Teensy and the transceiver. They do not correlate to CAN-H/CAN-L.
• TXD/RXD do not need to be twisted pair. Keep them short and tidy.
• CANH/CANL should be twisted pair.
• If your transceiver module has an RS, S, or standby/slope pin, configure it for normal high-speed operation according to that module's documentation. On many SN65HVD230-style boards, this means tying RS low.

Termination

Most cheap CAN trancievers include a 120 ohm resistor across CANH and CANL. In this inline bridge, each side connects into an existing vehicle/radio CAN segment, so extra termination is usually not wanted. MAKE SURE TO REMOVE THIS RESISTOR.

Display features:

• Audio and Navigation translation are both enabled by default.
• Navigation takes priority while route guidance is active.
• Navigation currently shows distance and street text only.

Serial Commands

Commands are sent over USB serial at 115200 baud. Most production settings are saved to EEPROM when changed. You can also use Arduino IDE's built in Serial Monitor.

General

Command	Description
h or help	Print command help.
s or status	Print bridge status, counters, feature flags, and current MFD text.
save	Persist current brightness, DDP, Audio, Nav, steering, and dimmer settings.
defaults	Restore known-good production defaults and save them.
reset	Clear runtime frame counters.
l or log	Toggle verbose dimming-frame logging.
b or bypass	Toggle bypass mode. In bypass mode, frames pass through without the brightness rewrite.

Screen Brightness / Dimming

Command	Description
day XX	Set the day/all-zero brightness byte. Example: day FD.
night XX	Set the low endpoint used by scaled dimmer mode. Example: night 20.
dim status	Print current dimmer mode.
dim pass	Pass dash-dimmer frames unchanged.
dim mirror	Copy the raw dimmer byte into the MIB2 brightness byte. Debug/fallback mode.
dim scale	Scale the dimmer wheel range into nightBrightness..dayBrightness.

dimmer can also be used as an alias for dim.

MFD Translation

Command	Description
ddp status	Print DDP status through the normal status output.
ddp on	Enable DDP/MFD display support and save it.
ddp off	Disable DDP/MFD display support and save it.
ddp audio	Debug-select the Audio DDP channel 0x680/0x681. Automatic priority may override this while driving.
ddp nav	Debug-select the Navigation DDP channel 0x682/0x683. Automatic priority may override this while driving.
ddp redraw	Force the current DDP page to be shown/redrawn again.
ddp log	Toggle verbose DDP protocol logging.

Audio Translation

Command	Description
audio status	Print audio-related status through the normal status output.
audio on	Enable BAP Audio to DDP Audio translation and save it.
audio off	Disable Audio translation
audio log	Toggle decoded BAP audio logging.
audio all	Toggle broad candidate BAP logging for IDs 0x660 through 0x66F. Debug only.
audio sniff	Toggle focused audio text/RDS sniffing on IDs 0x660 through 0x66F. Debug only.
audio test	Draw a manual Audio test line on the MFD.
audio clear	Reset Audio page text to default placeholders.

Navigation Translation

Command	Description
nav status	Print navigation-related status through the normal status output.
nav on	Enable BAP Navigation to DDP Navigation translation and save it.
nav off	Disable Navigation translation
nav codes	Toggle raw maneuver code display, such as M35. Debug only; default is off.
nav sniff	Toggle focused nav sniffing on 0x67C, 0x67D, and 0x3A2. Debug only.
nav test	Draw a manual Navigation test line on the MFD.
nav clear	Clear Navigation text and route state.

navigation can also be used as an alias for nav.

Steering Wheel Button Integration

Command	Description
steering status	Print steering-related status through the normal status output.
steering on	Enable MFD up/down to radio previous/next translation while the Audio page is actively showing.
steering off	Disable steering previous/next translation
steering log	Toggle steering button logging.