Documentation Autoaddressing

Explanations Regarding Topology Of The LIN Bus And Auto-addressing

Knowledge of the arrangement of the stepper motors, i.e. the manner in which the stepper motors are interconnected on the LIN bus (topology), and of the function sequence of auto-addressing can be enormously helpful in determining the cause of a fault.

The stepper motors of the climate control are connected across a LIN bus to the control module of the climate control. The stepper motors communicate with the control module of the climate control across this LIN bus. Communication is by means of messages. These messages contain information such as the position to which a stepper motor is to move or faults detected by the stepper motor.

Topology:
The stepper motors are switched in series on the LIN bus. This means that the LIN bus in the wiring harness of the climate control is routed from the control module to the first connector in the wiring harness. Connecting the stepper motor to the connector routes the LIN bus to the next connector etc. The LIN bus is thus looped through each stepper motor. The first stepper motor is the topological first stepper motor in the LIN bus chain viewed from the control module of the climate control. The last stepper motor in the chain also the topological last.

The stepper motors on the climate control are all the same. During operation, the only difference between them is their programmed address. The address ensures that the stepper motor knows messages are addressed to it (e.g. open defroster flap) and/or that the control module knows which stepper motor sent a fault message.

Each air distribution flap in the climate control is assigned to a certain address. The control module of the climate control knows if e.g. information is to be sent to the defrosting-flap motor that a corresponding message must be sent with the destination address e.g. 21. This address must be programmed into the stepper motor attached to the defroster flap. The address determines what function the stepper motor assumes in the composite system.

If one or more stepper motors have no expected address (e.g. after replacement), they cannot communicate with the control module climate control (no response). The stepper motors must be addressed. This must be initiated via the control module of the climate control. Requirements for successful addressing of the stepper motors are correct encoding of the control modules of the climate control (so that it knows which version of the climate control is fitted in the vehicle), a stable power supply to the stepper motors, and a fault-free LIN bus connection up to the topological last stepper motor

After starting the auto-addressing, the address of the topological last stepper motor is programmed (e.g. on the F01 the fresh-air-flap motor is given the address 22). Then the topological next-to-last stepper motor is given its address etc. until all the addresses have been assigned. The position of the stepper motor in the wiring harness thus determines the address programmed into the stepper motor and thus which function it assumes.

If for example the topological last stepper motor is not connected to the wiring harness of the climate control during auto-addressing or if the LIN connection to the stepper motor is interrupted, auto-addressing of the topological next-to-last stepper motor would be detected incorrectly as the topological last stepper motor and thus assigned the wrong address. The remaining stepper motors are also given an incorrect address.

Incorrect addressing also occurs after the replacement of connectors, as a stepper motor attached to an air distribution flap then has a topologically incorrect position in the wiring harness.

The topology of the stepper motors is reflected in the following tables. The first stepper motor in the table is the topological first; the last stepper motor in the table is the topological last.

Topology (1 corresponds to the first stepper motor viewed from the control module):







HKA Topological order
1 Left-hand mixed-air flap motor
2 Left-hand air distribution flap motor
3 Right air distribution flap motor
4 Right mixed-air flap motor