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What’s New About CAN FD?
Jessica Hopkins

CAN, Controller Area Network, was created to improve vehicles as well as reduce the cost and maintenance of internal wiring – which was quickly increasing as more features were moving from mechanical to electronic technologies. For interaction and control, a protocol was required to handle the increasing complexity of operative devices within a vehicle.

CAN Background

The CAN protocol was introduced by the company Robert Bosch in 1986. CAN allowed multiple devices, or nodes, to be able to communicate with each other on a single line and without the need of a centralized host computer. It also incorporated a unique feature, called message arbitration, where each node could allocate prioritization of a message with each other based on the identifier being sent on the network.

Introduction of CAN FD: Flexible Data-Rate

As increasingly complex systems such as driver assistance systems, parking aids, and blind-spot detection are incorporated into the newer vehicles of today, there comes a need for greater bandwidth on the CAN bus. However, adding additional CAN networks to one vehicle would only weigh it down and decrease efficiency. To meet the need for increased bandwidth, an extension of the CAN protocol was introduced in 2012, called CAN FD, also known as CAN flexible data-rate. This new extension offered the ability to transmit data at rates up to 8 Mbps, greater than the initial 1 Mbps offered by the original CAN protocol.  It also extended the bit length of a message from 8 bytes to 64 bytes. Together, these new changes created a more efficient way to send data on the bus, while allowing more utilizations of the protocol in various developments.

CAN FD Features and Applications

CAN is used in a variety of applications, including defense, industrial automation, autonomous devices, underwater vehicles and medical equipment. However, the design of CAN FD was initially created to meet the developing needs of automakers.

In autonomous vehicles and newer car models, ECU’s (Electronic Control Units) and sensors are used frequently. CAN FD allows these components to operate at the highest speeds with larger payload, all while reducing the bus load which could impede performance. The software programming time in vehicle ECU’s is even reduced to up to a fifth of the average time, and auto engineers running diagnostics or software upgrades can do so in the quickest times yet.

In addition to speed and larger data size, CAN FD has improved error detection. The extra bits in the CRC frame improve the performance of the CRC-algorithm, as it provides better protection of the data content. The addition of the ESI (Error State Indicator), also improves error detection by including a state of the transmit node where the bits are monitored by the receiver and errors can be easily detected. Normally, the ESI bit is transmitted as dominant, but if the sender frame becomes error-passive, the ESI bit will become recessive, indicating failure in the system. This process ensures safety for passengers because the errors will be caught early on. Because of these benefits of CAN FD, automobiles using this protocol are consequently thought to be more reliable, safer, and more fuel efficient.

CAN FD Advantages

Along with automotive applications, other industries, including industrial, find this protocol useful for similar reasons. Having the larger payload is a major benefit in operating machinery as it results in reduced overhead. Position sensors in industrial settings can take advantage of this outcome to improve system responsiveness. The increase in data speeds is also helpful in industrial applications involving flash programming or data downloads. With higher speeds and larger payloads, overall throughput of the network is improved.

CAN has been a well-known and widely used protocol for multiple decades, and the CAN FD extension will soon become a preferred protocol for automotive and industrial uses.

Total Phase offers CAN tools with free API for engineers to create custom applications for their unique projects. Check out our CAN tools here.  If you’d like to be updated on Total Phase developments for CAN and CAN FD, please send us a message at sales@totalphase.com.