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CAN FD takes-off

At the Embedded World exhibition in Nuremberg (Germany) Bosch demonstrated a running CAN FD network. Kvaser and Peak presented their FPGA implementations of the improved CAN protocol, as well. Several software and toolmakers announced CAN FD support.

CAN FD network by Bosch (left) with twelve nodes and by Peak (right) with two nodes and an analyzing tool interpreting the improved CAN frames
THE IMPROVED CAN PROTOCOL (also known as CAN FD), already submitted by CiA for international standardization, takes-off. One year ago, it was officially introduced by Bosch (Germany) on the 13th international CAN Conference in Germany. Some additional information was given in Detroit in the 1st CAN FD Tech Day. At the Embedded World exhibition Bosch showed on its booth only its CAN FD demonstrator, no other products. This was a strong commitment. The CAN FD system comprised 12 nodes. The overall network had a length of 70 m. The arbitration bit rate was set to 500 kbit/s, which is normally used in most of the powertrain networks in passenger cars. The data-phase speed was 10 Mbit/s. The nodes use Bosch’s FPGA implementation supporting payloads of up to 64 byte. The physical layer was based on state-of-the-art transceiver chips. Of course, the CAN FD system was running under laboratory conditions. Meaning, you will not achieve the same results in outdoor environments, especially on temperatures below 0 °C. According to Mr. Mutter from Bosch, the bit-time settings are much more critical than in classic CAN solutions. Synchronization failures in the arbitration phase may cause serious problems, when the arbitration bit-rate is significant lower than the data-phase speed. For example: when the arbitration speed is just 125 kbit/s, it could be hard to achieve 10 Mbit/s in the data phase. There is also to consider that the clock frequency needs to be in minimum 40 MHz for a transmission speed of 8 Mbit/s. Bosch recommends to agree on clock rates of 20, 40, and 80 MHz depending on the desired maximum bit-rate.
Peak (Germany) has also implemented the improved CAN protocol (also known as CAN FD) in an FPGA. The company offers since several years FPGAs implementing the classic CAN protocol. Uwe Wilhelm and Alexander Gach, CEOs of Peak, presented also CAN FD support for its analyzing tools. Kent Lennartsson from Kvaser showed its CAN FD implementation on CiA’s booth.
CiA will set-up interoperability test systems for CAN FD, soon. The nonprofit association will provide different network topologies (bus-line and star) and test if CAN FD nodes can communicate correctly without causing error frames. Within the ISO the improved CAN protocol will be standardized. The C & S Group is preparing a CAN FD conformance test plan and its implementation. But this is not sufficient. Therefore, CiA has established several task forces to specify or recommend the usage of CAN FD networks. Therefore, CiA’s task force will specify the physical layer implementations (bit-time settings, transceiver parameters, etc.) for different applications. In addition, the user interface of CAN controller chips supporting the classic and improved protocol needs to be standardized partly in order to simplify the development of low-level driver software. The third topic to be discussed and harmonized is the system design, especially the combination of classic and improved CAN communication in a network system architecture.
The chipmakers have also announced to implement CAN FD in its future micro-controllers. End of January Bosch has given its CAN FD core supporting payloads of up to 64 byte to Freescale (USA) and ST Microelectronics (France/Italy). The US company will provide first samples within the next weeks. The French-Italian chipmaker will follow in summer with ST32 micro-controllers with on-chip CAN FD modules. Renesas (Japan) is expected to deliver micro-controllers with CAN FD by end of the year. Other chipmakers may enclose their CAN FD road-maps during the CAN FD Tech Day.
Vector (Germany) has prepared its hardware interfaces to run CAN FD. Also the tools are ready to interpret the improved CAN frames and analyze them. Etas’s (Germany) open-source Busmaster analyzing tool is already CAN FD capable and was shown on Bosch’s booth at Embedded World. Other toolmakers are waiting for CAN FD hardware. Protocol stack providers are also ready to support CAN FD. Emtas (Germany) has prepared their CANopen protocol stack to support CAN FD. However, CiA has first to improve and standardize the CANopen application layer (CiA 301). It is expected that the future CANopen specification will allow PDOs with 64-byte length. Also the SDO protocol is expected to be improved meaning that the 64-byte messages will be used.