Safe CAN- and LIN-bus data transmission with AUTOSAR and customized CRCs
Hackers are able to harmfully influence the software of control units inside vehicles. To prevent such danger when transmitting framedata on the CAN- or LIN-bus the CRC (cyclic redundancy check) has become a good method for ensuring safety. A sent frame will only be accepted and processed by the recipient if the received CRC is correct. The development partnership AUTOSAR has defined a CRC standard with the help of two different profiles.
Profile 1 extends the input data of the frame by a constant, which use will be influenced by the chosen version (1A 16Bit, 1A 8Bit, 1B, 1C). Furthermore a counter will be simulated in the data field (see fig. 1).
Fig.1 - AUTOSAR CRC profile 1
Profile 2 has a counter in the data as well, which is additionally used for choosing a value from a constant 16 value storage (see fig.2). Hence the variance comes from the different versions and the constant in profile 1 and the 16 value storage in profile 2.
Fig.2 - AUTOSAR CRC profile 2
AUTOSAR has defined and standardized the starting position of the input block, length of the input block, starting position of the CRC, starting position of the counter, length of the counter, start and end value of the counter and the CRC values. All of our Baby-LIN devices live up to this standard in due form and not just that - projects of customers that deviate from this standard and insert customized values have already been and will always be supported by our products and the universal CRC variations they offer. Thus the LIN- and CAN-adapters from Lipowsky Industrie-Elektronik are prepared for every deviation using 14 to 28 adjustable parameters and allow a wide use in the development and testing environment.