Reversing camera (RFK), function - GF54.65-P-0005FQB

MODEL 218.9 up to model year 2015 with CODE 218 (Rear view camera)

Fig 1: Reversing Camera Block Diagram

Courtesy of MERCEDES-BENZ USA

Function requirements, general

Terminal 15 ON
Reversing camera function activated through the COMAND controller unit
Liftgate closed

The status of circuit 15 is sent by the electronic ignition lock control unit via the interior CAN, front SAM control unit and front end CAN (up to 28.02.2013) or chassis CAN 2 (as of 01.03.2013) to the reversing camera. The trunk lid/liftgate rotary tumbler switch detects the status of the liftgate. The rear SAM control unit reads in the status of the trunk lid/liftgate rotary tumbler switch directly and sends the status via the interior CAN, front SAM control unit and front end CAN (up to 28.02.2013) or chassis CAN 2 (as of 01.03.2013) to the reversing camera.

If the liftgate is not closed, the picture shown on the Audio/COMAND display is overlaid with a warning message and the guide lines are hidden.

During initial startup, when working on the reversing camera or when working on the liftgate, the reversing camera has to be calibrated again using the diagnosis tester.

Reversing camera, general

The reversing camera is an optical parking and maneuvering aid. Its tasks include a surrounding field recording of the rear driving area, the generation of dynamic guide lines and the sending of the image data to the COMAND controller unit. The pictures captured by the reversing camera are processed accordingly by the reversing camera and shown in the audio/COMAND display. The current driving path is shown on the audio/COMAND display on the basis of the vehicle dimensions, vehicle speed and steering angle.

Reversing camera function sequence

Engagement of gear range "R" activates the reversing camera.

The fully integrated transmission control unit sends information on the engaged gear range over the drive train CAN, CDI control unit or the ME-SFI [ME] control unit, chassis CAN (up to 28.02.2013) or the chassis CAN 1 (as of 01.03.2013), front SAM control unit and the front end CAN (up to 28.02.2013) or chassis CAN 2 (as of 01.03.2013) to the reversing camera.

The reversing camera then actuates the COMAND controller unit over the front end CAN (up to 28.02.2013) or chassis CAN 2 (as of 01.03.2013), the front SAM control unit and the interior CAN. The pictures captured by the reversing camera are read in and processed as CVBS signals.

To enable an improved display of the driving area to the rear, electronic distortion correction is also conducted through the reversing camera in addition to the optical distortion correction by the lens previously performed.

The reversing camera transmits the processed pictures as CVBS signals to the COMAND controller unit. The COMAND controller unit then activates the Audio/COMAND display over the telematics CAN (CAN A). The pictures processed by the reversing camera are then transmitted by the COMAND controller unit directly via the LVDS line to the Audio/COMAND display and shown there. The reversing camera calculates guide lines taking into account the steering angle and the stored vehicle parameters; these lines are shown on the displayed pictures.

The steering angle is recorded by the steering angle sensor.

The steering column tube module control unit reads in the signals from the steering angle sensor directly and sends them over the chassis CAN (up to 28.02.2013) or chassis CAN 1 (as of 01.03.2013), front SAM control unit and front end CAN (up to 28.02.2013) or chassis CAN 2 (as of 01.03.2013) to the reversing camera.

The reversing camera function enables the driver to select between the following parking modes:

Maneuvering mode
Trailer mode (with CODE 550 (Trailer hitch))

The corresponding selection takes place at the operating level of the COMAND controller unit.

If the reversing camera was previously operated in maneuvering mode, the maneuvering mode is activated again when the "R" gear range is engaged. This does not apply when the reversing camera was previously operated in trailer mode.

Maneuvering mode

The maneuvering mode assists the driver when reversing while parking. In doing so, dynamic guide lines are also shown on the Audio/COMAND display in addition to the pictures recorded by the reversing camera.

Display of dynamic guide lines (with wheels in straight-ahead position)

Fig 2: Display - Dynamic Guide Lines Screen (With Wheels In Straight-Ahead Position)

Courtesy of MERCEDES-BENZ USA

Display of dynamic guide lines (with wheel turned to the right)

Fig 3: Display - Dynamic Guide Lines Screen (With Wheel Turned To Right)

Courtesy of MERCEDES-BENZ USA

Virtual steering angle (yellow guide lines):

The yellow guide lines are shown as soon as the driver turns the steering wheel. They indicate to the driver the path which the vehicle would follow with the current steering wheel angle. This curve is automatically adapted to the situation as the steering angle changes. The distance between the yellow guide lines is slightly more than the vehicle width.

Parking procedure:

In order to park, the driver must now adapt the steering angle until an outer line of the yellow guide lines in the audio/COMAND display touches the parking space marking. This parking space marking can, e.g. be another vehicle or a line on the asphalt. The driver must then continue reversing and adapting the steering angle until the displayed parking space limits run parallel to the current direction of travel. Next the driver must turn the steering wheel back into the straight-ahead position in order to drive in a straight line up to the final park position in the parking space.

The distance lines inform the driver of the distances between the virtual bumper and obstacles.

Display of distance lines in the maneuvering mode

Fig 4: Display - Distance Lines Screen (Maneuvering Mode)

Courtesy of MERCEDES-BENZ USA

Trailer mode (with CODE 550 (Trailer hitch))

Trailer mode supports the driver when reversing to a trailer by zooming into the ball head. When reversing, special guide lines are also shown on the Audio/COMAND display in addition to the pictures recorded by the reversing camera.

Display of distance lines in the trailer mode

Fig 5: Display - Distance Lines Screen (Trailer Mode)

Courtesy of MERCEDES-BENZ USA

Virtual steering angle (yellow guide line)

As soon as the driver turns the steering wheel, this yellow guide line is displayed. They indicate to the driver the path which the vehicle would follow with the current steering wheel angle. This curve is automatically adapted to the situation as the steering angle changes. The yellow guide line is shown at a distance of approx. s = 1 m to the trailer hitch. Distance line around the ball head (red guide line):

The red distance line is shown permanently on the Audio/COMAND display and notifies the driver about the distance over a radius of 0.25 m around the ball head.

The guide lines are hidden for an attempted correction (forward travel) in the Audio/COMAND display and shown again when gear range "R" is engaged again taking the following parameters into consideration.

t < 10 s
v < 10 km/h
s < 10 m forward travel

If these parameters are exceeded the picture recorded by the reversing camera is no longer shown on the Audio/COMAND display. The reversing camera then remains in standby mode. The vehicle speed and direction of travel are determined via the wheel speeds and wheel rotation directions. The Electronic Stability Program control unit sends the information about the wheel speeds and wheel rotation directions over the chassis CAN (up to 28.02.2013) or chassis CAN 1 (as of 01.03.2013), front SAM control unit and front end CAN (up to 28.02.2013) or chassis CAN 2 (as of 01.03.2013) to the reversing camera.

Electrical function schematic, reversing camera		PE54.65-P-2051-97XAC
Overview of system components of parking assistance systems	MODEL 218.9 up to model year 2015 with CODE 218 (Rear view camera)	GF54.00-P-9997FQ