Operating, display unit with control unit, function - GF82.85-P-3114-08BA
In vehicles as of 01.09.03, all audio signals, voice signals and navigation processor (N41/1) signals are transferred via the Media Oriented System Transport (MOST).
In vehicles from 01.09.03 onwards, the audio gateway control unit (N93/1) is also installed as interface between the class B (interior) Controller Area Network Bus (CAN-B) and the Media Oriented System Transport (MOST). The audio signals are then sent to the audio gateway control unit (N93/1) and output via the vehicle speakers.
Processing button and switch operations
The controls on the function keypad in the COMAND operating, display and control unit (A40/3) are read in via microcontroller I/O ports and made available to the central computer.
Depending on the system function, the control actuations are processed in the central computer and transferred to the other system components via the digital data bus (D2B) and CAN-B in the form of a data telegram.
Graphic editing and image output
The graphic subsystem edits and outputs the operating displays. The operating screens are internally output to the display by the graphics system via the RGB output.
The RGB signal contains the information and amplitudes for the three primary colors of red, green and blue, and a synchronization signal. The actuation electronics in the display unit evaluate the RGB signal and actuate the color and intensity of the individual pixels line by line.
A horizontal synchronization pulse occurs at the end of each line.
The electronic circuitry of the display unit then starts the next line. When the last line of the display has been reached, a vertical synchronization pulse occurs, and the electronics actuate the first line again.
Audio signal output
The audio signals from the various sources (Radio, CD, navigation system voice output etc.) are prepared by the COMAND operating, display and control unit (A40/3n1) and amplified before being output via the vehicle speakers. In vehicles with code (810) sound system, the final amplification of the audio signals is carried out by the sound amplifier (A2/13). The audio source data are transmitted to the sound amplifier (A2/13) via the digital data bus (D2B) for this purpose.
Info menu as of 1.6.01
The Info menu is accessed directly using the "i button" or the "INF button". This functionality can be selected independently of source (e.g. from the telephone or radio menu).
You can return to the screen from which "Info" was selected by pressing the Back key. If the Mode item was selected in the Info menu, the system switches to the screen that was accessed prior to the Info menu when the Back key is pressed.
On-board diagnosis, shown in display
The following information is incorporated in the Info menu: up to 31.05.01
- Warm start (operating condition)
- Battery voltage (e.g. 13.21V)
Added as of 01.06.01
- GPS, item number (number and position of available satellites)
- Direction of travel
- Speed (mph)
At least 4 satellites are required for dead reckoning, 3 satellites are sufficient for other calculations.
If these conditions for position calculation are not met, only the number of satellites appears in the display.
Diagnosis interface (K-line) and D2B component fault management
During COMAND operation the system stored all faults that have occurred in non-volatile memory. These can be read out via the diagnostic interface (K-line) using STAR DIAGNOSIS. Output of the errors on the display unit is not possible. The COMAND fault management also includes the connected components (e.g. communication with D2B equipment). Each D2B component has its own fault memory. The faults are transferred via the D2B bus to the COMAND operating, display and control unit (A40/3) upon request by STAR DIAGNOSIS and can then be read out via the diagnostic interface.
Navigation and GPS control unit
The navigation processor is the central component of the COMAND navigation system.
It is integrated in the COMAND operating, display and control unit (A40/3) and calculates the location of the vehicle from the incoming signals. It also calculates the vehicle's route after the destination has been entered.
The GPS control unit is part of the navigation processor.
In model 220 it analyses the satellite signals received by the GPS antenna (A2/49a2) or in model 215 by the GPS antenna (A2/23) and uses them to calculate the vehicle position.
Yaw rate sensor
The yaw rate sensor determines the direction changes of the vehicle. It is installed in the navigation processor. Calibration is not required.
In vehicles from 01.06.00 onwards, the traffic data recorder (A2/43) is also integrated in the COMAND operating, display and control unit (A40/3).
In vehicles from 01.09.03 onwards, the navigation processor (N41/1) is installed as a separate control unit in the left of the trunk.
The CD drive of the COMAND operating, display and control unit (A40/3n1) reads data from the CD that has been inserted and makes it available to the navigation processor via the internal data bus.
After the activation of the navigation system, the following instruction appears on the display:
- Up to 31.8.03: "Please insert Navi CD type DX"
- As of 01.09.03: "Please insert Navi DVD"
In vehicles from 31.8.03 onwards it is possible to play audio CDs after loading and during navigation.
The navigation CD contains the following information:
- Program data for execution in navigation processor
- Voice data for voice output
- Map data.
The digitized map area on the CD contains towns, streets, intersections and their attributes (e.g.: one-way streets, turn prohibitions etc.).
It does not contain information about company and private land, farms, housing estates and paths.
Cassette player (up to 31.08.02)
The cassette flap is moved in and out, opened and closed by a motor.
When the cassette tape is being played it is led past the reading head of the cassette player at a constant speed.
In order to reduce noise during cassette playback, noise suppression measures (e.g. DOLBY B or DOLBY C) are required.
The audio signal voltage that is generated is amplified in the cassette player and relayed to the audio components of the COMAND operating, display and control unit (A40/3).
DOLBY B reduces tape hiss in the high frequency range. Signals that are weak and in the upper sound range are amplified during recording. Using DOLBY B during playback of a cassette, the signals that were amplified during recording are reduced to the original level. This measure reduces the noise level. DOLBY C is a further development of DOLBY B.