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Body Electronics

AUTOSAR Basic Software for CAN-MOST Gateways

January 12, 2011 | Patrick Markl | 222901315
AUTOSAR Basic Software for CAN-MOST Gateways AUTOSAR supports multi-channel ECUs. Two basic software modules, PDU and COM, route so-called PDUs (Protocol Data Units) between two bus systems. Together with the corresponding bus driver layers, routing is possible between CAN, LIN, FlexRay and Ethernet buses. Since interfacing to a MOST bus is not yet defined in AUTOSAR, a solution must be found for implementing a CAN-MOST gateway. Vector Informatik presents three approaches and discusses the advantages and disadvantages of each.
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Networking in modern vehicles is based on several different bus systems. CAN, LIN and FlexRay are used in the body and power train areas. Multimedia and infotainment ECUs are networked primarily over the MOST bus. The exchange of information between networks is the task of gateway ECUs. They exist in various forms ranging from relatively simple gateways that only exchange minimal information between buses of the same kind to central gateways that interface to several buses of different types.

AUTOSAR offers ECU developers a solid software basis for interfacing their ECUs to CAN, LIN, FlexRay and Ethernet buses. Gateway tasks are handled by various software modules of the AUTOSAR architecture (Figure 1), depending on the specific functionality that is required.

Figure 1: Rough architecture of an AUTOSAR ECU

Routing Mechanisms in AUTOSAR

Per AUTOSAR specification, three mechanisms are available for routing data, each of which covers different use cases:

- PDU routing

- Signal routing

- Transport protocol routing, e.g. for diagnostic data

The PDU gateway is part of the PDU router (PDUR), and it routes entire data packets, the Protocol Data Units (PDUs), from one network to another. This type of routing assumes that the PDUs are defined in the same way on both the source and target networks, which means that the length and content of the PDUs must match. However, it should be noted that PDU routing is spontaneous routing: A PDU is routed as soon as it is received. Therefore, it is not possible to change the cycle time or send type. However, in some cases such conversions are necessary. Then routing must be performed over a signal gateway.

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