Navigation, function

P82.61-A001-79

P82.61-A002-79

Function requirements for map navigation, general

 Circuit 30t

 Transport mode not active

 Authorized SD card (Secure Digital) for code 357 (Map navigation) is inserted into the SD card slot of the multimedia connection unit.

 Signals are available from at least 4 GPS satellites (global navigation system).

 Head unit is switched on.

 The SD card is authorized for the respective head unit and can then only be used for this head unit.

Map navigation, general

With map navigation, the head unit is supported by the following vehicle components:

 Map data (including data on maximum permissible speed) from the SD card over the multimedia connection unit

 GPS signals from HERMES control unit (with code 362 (HERMES LTE) as of 01.06.2019)

 GPS signals from GPS antenna (except code 362 (HERMES LTE) or with code 362 (HERMES LTE) up to 31.05.2019)

 Wheel speed signals from the Electronic Stability Program control unit, via the electronic ignition lock control unit

 Reverse gear signal from electronic ignition lock control unit

 Activation of the menu via the upper control panel control unit

 Operation through Audio/COMAND control panel (except code 446 (Touchpad only)) or through the touchpad (with code 446 (Touchpad only) or with code 448 (Touchpad))

 Operation via the head unit multifunction steering wheel button group

 Operation via the driver hands-free system microphone

 Audio output through front vehicle speakers, including audio reduction, with code 810 (Sound system) through the sound system amplifier control unit, for model 257.361, model 290 except code 810 (Sound system) over the Midline sound system amplifier control unit

 Volume control of the audio output through the volume control button in the right lower control panel or through the volume adjustment switch in the head unit multifunction steering wheel button group

 Video output and map display on the Audio/COMAND display, and also on the instrument cluster

 Traffic Message Channel (TMC) or comparable radio traffic messages through the radio tuner integrated into the head unit (except code 367 (Live Traffic Information) with a valid subscription for real-time traffic data)

 Real-time traffic data from the HERMES control unit (with code 367 (Live Traffic Information) and a valid subscription for real-time traffic data)

 Updates of map data over SD card on a PC connected to the Internet

 Updates on the SD card takes are downloaded externally on an Internet-capable PC; this is described in the operator's manual.

Function sequence for map navigation

The head unit accesses the map data on the SD card via a USB connection (Universal Serial Bus) to the multimedia connection unit.

 When the SD card is used for the first time in the vehicle, data is written to a configuration file on the SD card by the head unit.

The head unit receives the GPS signals via a direct line from the HERMES control unit (with code 362 (HERMES LTE) as of 01.06.2019) or from the GPS antenna (except code 362 (HERMES LTE) or with code 362 (HERMES LTE) up to 31.05.2019).

 As GPS operates in the gigahertz range and the signals are weak, the following events may lead to reception interference: Atmospheric interference (e.g.bad weather, water vapor, fog), multiple reception through signal reflexions (e.g.on building walls) or signal shadowing (e.g.in built-up areas, in tunnels, in the vicinity of tall buildings of trees).

In the event of a failure of the GPS signals, the head unit reverts back to the basic position finding. For basic position finding, the head unit evaluates the data from the integrated gyro sensor as well as the wheel speed signals and the reverse gear signal.

The wheel speed signals are transmitted via the following route:

Electronic Stability Program control unit 

Suspension FlexRay 

Electronic ignition lock control unit 

User interface CAN 

Head unit

The head unit receives the reverse gear signal from the electronic ignition lock control unit via the user interface CAN.

 Position finding errors in position finding, rolling backwards with "circuit 15 OFF" (ignition switched off) or transport of the vehicle falsify the basic position finding. In both instances, the deviation is automatically corrected by the navigation processor integrated in the head unit upon reception of GPS data.

The operation signal from the upper control panel control unit is read in over the following route:

LCP LIN 

Audio/COMAND control panel (except code 446 (Touchpad only)) or Touchpad (with code 446 (Touchpad only)) 

Telematics CAN 

Head unit

On model 257, the operation signal of the volume control button in the right lower control panel is forwarded as follows:

LCP LIN 

Audio/COMAND control panel (except code 446 (Touchpad only)) or Touchpad (with code 446 (Touchpad only)) 

Telematics CAN 

Head unit

On model 290, the operation signal of the volume control button in the right lower control panel is forwarded as follows:

Drive Unit CAN 

Drive Unit control unit 

LCP LIN 

Audio/COMAND control panel (except code 446 (Touchpad only)) or Touchpad (with code 446 (Touchpad only)) 

Telematics CAN 

Head unit

The operation signals of the head unit multifunction steering wheel button group, including the volume adjustment switch, are sent over the following route:

Steering wheel electronics 

Steering wheel CAN 

Steering column tube module control unit 

Suspension FlexRay 

Electronic ignition lock control unit 

User interface CAN 

Head unit

The operation signals are sent from the Audio/COMAND control panel (except code 446 (Touchpad only)) or from the Touchpad (with code 446 (Touchpad only) or with code 448 (Touchpad)) over the telematics CAN to the head unit.

The head unit receives the voice inputs from the driver hands-free system microphone via a direct line.

On model 257 (except 257.361) except code 810 (Sound system), the head unit forwards the voice output to the speaker system.

For model 257.361, model 290 except code 810 (Sound system) the head unit sends the voice outputs over MOST to the MIdline sound system amplifier control unit.

In vehicles with CODE 810 (Sound system), the head unit transmits the voice output via the MOST to the sound system amplifier control unit.

The head unit switches on the Audio/COMAND display via the telematics CAN. The picture signals are transferred by the head unit via an HSVL line to the Audio/COMAND display. The head unit sends the signals for display in the instrument cluster to the instrument cluster via user interface CAN.

On vehicles except code 367 (Live Traffic Information) with a valid subscription for real-time traffic data, the navigation processor in the head unit takes the radio traffic messages into account. The radio traffic messages are sent to the navigation processor within the head unit by the integrated radio tuners.

On vehicles with code 367 (Live Traffic Information) and a valid subscription for real-time traffic data, the HERMES control unit receives real-time traffic data over the emergency call system 1 antenna (model 257), the left telephone antenna, right telephone antenna and the telephone antenna splitter (model 290) and over the emergency call system 2 antenna, as long as it is in the geographical area for which the traffic data service is offered.

 At the end of the subscription or outside of the geographical area for which the traffic data service is offered, the radio traffic messages are evaluated for dynamic route guidance.

The HERMES control unit sends the real-time traffic data as WLAN signals over the integrated radio interface to the WLAN antenna, which forwards the signals to the head unit.

The HERMES control unit receives position data from the head unit at regular intervals in the opposite direction. The HERMES control unit sends the position data from the head unit over the emergency call system 1 antenna (model 257), the left telephone antenna, right telephone antenna and the telephone antenna splitter (model 290) and over the emergency call system 2 antenna to the service provider. The HERMES control unit therefore contributes to collecting the traffic information from which the map navigation then benefits.