A low cost and flexible approach to CAN conformance testing

Since its introduction in the early 1980's, CAN has become the de-facto communications protocol employed in vehicle and industrial control applications. Before any new product can claim to support CAN-connectivity, compliance with the protocol at the physical and data link layers must be tested and verified. To help standardize the requirements for such testing, ISO has set a draft standard specifically for CAN conformance testing. Traditionally, CAN controllers and transceivers have been implemented at the silicon level, either in the form of dedicated ICs or as on-chip peripherals of embedded devices. The practical implementation of CAN conformance testers has been realised using dedicated hardware and specially written analysis software; this is a practical approach when testing and verifying conformance prior to high-volume IC manufacture. However, recent years have seen an increased interest in the employment of CAN-connected devices implemented by programmable logic devices such as FPGA's. Such 'soft core' implementations are often in small-volume (or even one-off) batches. In such circumstances, for cost and availability reasons, it may not be practical for developers to use traditional CAN-conformance testing equipment. To help alleviate this problem, this paper proposes a low-cost and easily implemented method which will allow developers to fully test a CAN soft core implementation. The method is based around simple off-the-shelf development boards and the simple analysis tool Chipscope, and allows developers to verify a CAN core against the relevant ISO standards. Finally, the paper describes the use of the test bed in the verification of an open-source CAN soft core implementation.