Patrick Markl, Vector Informatik
1/13/2011 12:47 AM EST
Because interfacing to a MOST bus is not yet defined in AUTOSAR, a solution must be found for implementing a CAN/MOST gateway.
Here are three approaches, with the advantages and disadvantages of each. AUTOSAR supports multi-channel ECUs. Two basic software modules, PDUR 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. Because interfacing to a MOST bus is not yet defined in AUTOSAR, a solution must be found for implementing a CAN-MOST gateway. Here are three approaches and the advantages and disadvantages of each.
Networking in modern vehicles is based on several different bus systems. CAN, LIN, and FlexRay are used in the body and powertrain areas. Multimedia and infotainment ECUs are networked primarily over the MOST bus. The exchange of information between networks is the task of gateway ECUs. These ECUs 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 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, depending on the specific functionality that is required.
While a CAN-MOST gateway can be realized as a hybrid solution or by a complex device driver, any changes to routing rules come late in the design process. There are also excessive redundancy concerns and additional memory requirements.
But implementation of such a gateway with an AUTOSAR architecture
(as described in the complete feature story, courtesy of Automotive Designline Europe), lies in routing messages of uniform length, as it is on the CAN bus. One can think of implementation of further extensions of the MOST stack in the future to add additional functionalities. This includes routing data of variable size—e.g. a list with different numbers of telephone book entries. Similarly, MOST network management tasks could be handled by AUTOSAR modules.
With the Ethernet interfacing available in AUTOSAR, it will be possible to develop very powerful gateways with a MOST connection and thereby utilize the advantages of the AUTOSAR architecture.
Patrick Markl is a senior software development engineer responsible for concept development in the Embedded Software product line at Vector Informatik GmbH, Stuttgart, Germany. He can be contacted via [email protected].