Conformance Testing of Soft-Core Can Controllers: A Low-Cost and Practical Approach

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 device can claim to support CAN-connectivity, extensive conformance testing is normally required to demonstrate compliance with the protocol at the physical and data link layers. To help standardize the nature of the specific test plans and documentation required for this testing, the ISO has published a set of draft standards specifically for CAN conformance testing. To date, most commercial CAN controllers and transceivers have been implemented at the silicon level, either in the form of dedicated IC’s 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 programmable logic devices such as FPGA’s for the implementation of CAN controllers and CAN-enabled devices. Such ‘soft core’ implementations are often realised in small-volume (or sometimes even one-off) batches; in such circumstances, cost and availability reasons may dictate that developers simply cannot employ 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 allows developers to verify a CAN core against the relevant ISO standards using only (low-cost) off-the-shelf development boards, coupled with a simple analysis tool such as Chipscope. Finally, the paper extensively describes the use of the test bed in the verification of an open-source CAN soft core implementation.