A Fixed Length Payload Encoding for CAN

Controller Area Network (CAN) bus is a vehicle bus standard designed to allow microcontrollers and devices to communicate with each other within a vehicle without a host computer. CAN bus is a message based protocol designed specifically for automotive applications but now also used in other areas such as aerospace, maritime, industrial automation and medical equipment. The message is transmitted serially onto the bus using a Non-Return To Zero (NRZ) format and may be received by all nodes. In CAN frames, a bit of opposite polarity is inserted after five consecutive bits of the same polarity. This is called bit stuffing and is due to the NRZ coding adopted. The controller area network (CAN) bit stuffing mechanism, it is essential to ensure proper receiver clock synchronization in the network. So it introduces a significant, payload-dependent jitter on message response times, which may worsen the timing accuracy of a networked control system. This paper presents a software payload encoding scheme, which is able to guarantee that no stuff bits will ever be added to the data field by the CAN controller during transmission. As a result jitter is reduced considerably.