Head Unit, Component Description - GF82.85-P-3140LFM

Model 217, 222 

as of model year 2018 

Shown model 222.0 

Location 

The head unit is located in the center console.

Tasks 

The head unit has the following tasks:

• Central operating and display unit for the entertainment and communications systems integrated in the vehicle 
• Integration of smartphones 
• Evaluating and forwarding control signals 
• Reading in of input signals as well as actuation of output media and system components 

Central operating and display unit for the entertainment and communications systems integrated in the vehicle 

The head unit provides the user with a structured and uniform user interface for the following system components:

• Audio (e.g. radio, Bluetooth® audio, Secure Digital (SD) card, universal serial bus (USB) including integrated Media Interface for connecting iPhones® or media transfer protocol (MTP) devices)
• Telephony
• Internet (including wireless local area network (WLAN) hotspot)
• Voice control system (VCS [SBS])
• Navigation (map navigation with data from internal hard disk) including extended functions of navigation mode
• Digital operator's manual (interactive)
• Video, including TV (with CODE 865 (TV tuner))
• "In Car Communication" (facilitates communication in the vehicle by amplifying statements of the front seat passengers by outputting them through the rear speakers)
• Emergency call (with code 351 (Emergency call system (HERMES)))

The user interface is shown on the Audio/COMAND display (A40/8).

Using the "Vehicle functions" menu, equipment-dependent contents and functions of additional systems (e.g. climate control, seat adjustments) can be shown and controlled on the Audio/COMAND display.

Integration of smartphones 

The head unit enables the integration of smartphones. In order to ensure that the content is prepared in a vehicle-compatible way, only smartphone applications (apps) that have been developed for the following integration standards are supported:

• Android vehicle (Google)
• CarPlay (Apple)
• MirrorLink (Car Connectivity Consortium)

In order to be able to use the smartphone apps, the smartphone must be connected to USB connector 2 (A90/5x2) of the multimedia connection unit (A90/5) and the integration standard selected via the "Connect" menu.

If a smartphone is connected and an integration standard Android Auto or CarPlay is activated, then the head unit is set into a special operating mode ("Integration mode"), in which certain head unit functions cannot be used. The radio (AM and FM), vehicle settings and safety-related functions, such as the emergency call function or the breakdown assistance (with code 360 (HERMES UMTS) or with code 362 (HERMES LTE)), can still be used in any case.

With MirrorLink and Android Auto, there are the following usage restrictions for the telephony: Calls can only be made by way of the connected smartphone. Telephony with code 380 (Car telephony package) is not possible.

If an integration standard is activated, the head unit supports the smartphone apps in the following manner:

• Volume adaptation for all audio signals
• Forwarding of control signals (e.g. from the Audio/COMAND control panel (A40/9) (with code 448 (Touchpad)) or from touchpad (A105) (with code 446 (Touchpad only) or code 448 (Touchpad)), pressing and holding voice control system ON button (S111s4), pressing accept/terminate phone call button (S163/2s15) from the head unit multifunction steering wheel button group (S163/2))
• Forwarding of signals from driver hands-free system microphone (B25/20) and from front passenger hands-free system microphone (B25/21) (e.g. for voice control or telephony)
• Audio outputs (e.g. for voice control or telephony) via the speaker system or forwarding the signals to the sound system amplifier control unit (N40/3) (with code 810 (Sound system)) to the advanced sound system amplifier control unit (N40/7) (with code 811 (Advanced sound system))
• Muting radio reception in the head unit (mute function), e.g. for smartphone telephony
• Forwarding of position data (e.g. GPS signals (global navigation system), gyro sensor signals, wheel speed signals)
• Forwarding of video signals generated by the smartphone to the Audio/COMAND display
• Forwarding of status information for displaying in the instrument cluster (A1)

The smartphone applications themselves are not shown in the instrument cluster.

If the Smartphone is being used to make a call, the head unit sends the telephone signals from and to the smartphone via the Bluetooth® antenna (A2/91) with Android Auto, and with CarPlay via the USB connection to the multimedia connection unit.

Evaluating and forwarding control signals 

The head unit receives operation signals of the Audio/COMAND control panel (with code 448 (Touchpad)) via the telematics CAN (CAN A). The control signals from the lower control panel (N72) (with code 446 (Touchpad only)) are sent as follows:

Lower control panel LIN (LIN A3)

Touchpad (with code 446 (Touchpad only))

Telematics CAN

Head unit

The head unit evaluates the data and transmits function-specific CAN messages to the user interface CAN (CAN HMI). When the DYNAMIC SELECT switch (A40/9s19, N72s19) is operated, the head unit also shows the selected transmission mode on the audio/COMAND display.

Reading in of input signals as well as actuation of output media and system components 

The head unit transmits and receives signals via the following connections:

• CAN 
• Media Oriented System Transport (MOST) 
• Direct line 
• Ethernet 

CAN 

The head unit is a telematics CAN and user interface CAN subscriber:

• The head unit receives the following signals via the telematics CAN, for example:
  • Operation signals from the lower control panel via and from the touchpad (with code 446 (Touchpad only)) or from the Audio/COMAND control panel (with code 448 (Touchpad))
  • Status signals regarding the charge status of a mobile phone from the mobile phone cradle control unit (N123/8) (with code 897 (Wireless mobile phone charging)) or from the rear mobile phone cradle control unit (N123/10) (with code 898 (Wireless charging in rear))
  • Initialization data from mobile phone cradle control unit for the connection of an unauthorized mobile phone in the vehicle hierarchy (with code 899 (Multifunction telephony))
  • Reception of key codes from mobile phone cradle control unit for drive authorization (with code 896 (Vehicle access and drive authorization over mobile phone))
• The head unit transmits the following signals via telematics CAN, for example:
  • Control signals to the audio/COMAND display
  • Status signals, as well as the charge level request from mobile phone to mobile phone cradle control unit or to the rear mobile phone cradle control unit
  • Control signals for the display in lower control panel via touchpad (with code 446 (Touchpad only)) or to the audio/COMAND control panel (with code 448 (Touchpad))
• The head unit receives the signals of the multifunction steering wheel button group (S163/1) and the head unit multifunction steering wheel button group from the instrument cluster, e.g. via the user interface CAN.
• The head unit sends, for example, navigation displays to the instrument cluster via the user interface CAN, or interprets signals from the lower control panel (with code 446 (Touchpad only)), from the touchpad (with code 446 (Touchpad only)) or from the audio/COMAND control panel (with code 448 (Touchpad)) to the electronic ignition lock control unit (N73).

The control signals received from the lower control panel via the touchpad (with code 446 (Touchpad only)) and the audio/COMAND control panel (with code 448 (Touchpad)) are evaluated by the head unit, which then sends function-specific CAN messages to the user interface CAN. When the DYNAMIC SELECT switch is operated, the head unit also shows the selected drive program on the Audio/COMAND display.

Media Oriented System Transport (MOST) 

The head unit exchanges data with the following control units via MOST:

• Sound system amplifier control unit (with code 810 (Sound system))
• Advanced sound system amplifier control unit (with CODE 811 (Advanced Sound System))
• TV tuner control unit (N143) (with code 865 (TV tuner))
• Rear Seat Entertainment system controller unit (A26/18) (with CODE 864 (Rear Seat Entertainment system))

Direct line 

The head unit is equipped with the following direct connections:

• Circuit 30t
• Circuit 31
• FM, AM, CL, DAB and KEYLESS-GO antenna amplifier (A2/18) (input), DAB-Band-III signal (DAB I) (with code 537 (Digital radio (DAB))) (input)
• FM2, DAB and TV2 antenna amplifier (A2/138), DAB Band III signal (DAB II) (with code 537 (Digital radio (DAB))) (input)
• Multifunction antenna (A28/11) (model 222) or SDAR antenna (A2/82) (model 217) with code 536 (SIRIUS satellite radio) (input)
• Right emergency call system antenna (A2/55) and left emergency call system antenna (A2/54) (model 222 with code 536 (SIRIUS satellite radio) and code 503 (Pre-installation for Remote Parking Pilot)) (Input)
• Driver hands-free system microphone and front passenger hands-free system microphone (input)
• GPS signals:
  • As of 01.06.2019 with code 362 (HERMES LTE) from HERMES control unit (N112/9) (Input)
  • Up to 31.05.2019 or except code 362 (HERMES LTE) from the multifunction antenna (model 222) or from the GPS antenna (A2/49a2) (model 217) (Input)
• Muting of audio sources from the HERMES control unit (with code 362 (HERMES LTE) or code 360 (HERMES UMTS), except code 810 (Sound system), code 811 (Advance sound system)) (Input)
• HSVL line (High speed video link) from reversing camera (B84/3) (Input)
• HSVL line from parking system control unit (N62) (with code 235 (Active Parking Assist with PARKTRONIC) or with code P44 (Parking package)) (input)
• Bluetooth® antenna (input and output)
• WLAN antenna (A2/83) (input and output)
• Multimedia connection unit (input and output)
• Dedicated Short-Range Communications control unit (A50/6) (with code 498 (Japan version)) (input and output)
• External CD drive (accessories) (with code 320 (Pre-installation of single CD drive)) (input)
• HSVL line for picture and video data to the Audio/COMAND display (Output)
• HSVL line for high-resolution picture data to the instrument cluster (Output)
• Wake-up for MOST (output)
• Audio output (speaker) (except code 810 (Sound system), code 811 (Advanced sound system)) (output)
• Wake-up line to telephone antenna changeover switch, stationary heater and Remote Parking Pilot (A2/155) (with code B24 (Remote control for stationary heater), with code 503 (Pre-installation for Remote Parking Pilot) and with code 380 (Car telephony package), with code 899 (Multifunction telephony)) (output)
• Microphone output to the HERMES control unit (with code 360 (HERMES UMTS) or code 362 (HERMES LTE)) (output)
• Digital instrument cluster full display fan motor (M4/12) (output)

Ethernet 

Via Ethernet, the head unit receives software uploads for all MOST subscribers from the diagnostic connector (X11/4) connected to the diagnostic unit.

Structure 

The following components are integrated into the head unit:

• Arithmetic unit
• Hard disk with searchable database for audio files, including cover art, cover flow and Gracenote Database
• Receiver for Bluetooth® and Wireless Local Area Network (WLAN)
• 3 radio tuners for AM reception, FM phase diversity and separate FM tuner function for data services, e.g. traffic messages
• High Definition (HD) radio tuner (with CODE 494 (USA version))
• SDARS tuner (Satellite Digital Audio Radio Service) (with code 494 (USA version))
• DAB dual tuner (Digital radio) (except code 498 (Japan version) and except code 494 (USA version))
• 4-channel audio amplifier
• GPS receiver
• Gyro sensor and 3Dacceleration sensor
• Navigation processor and traffic data recorder
• Head unit electrical fuse (A26/17f1) in the combination connector at the rear panel

Wiring diagram of head unit

A26/17

PE82.85-P-2110-97SEA