Automotive and industrial use cases for CAN FD

Improved CAN Improved Dr. Tobias Lorenz

Author he main advantage of and immunity tolerances, it ment) is sent with the nom- CAN turned out to be a is commonly used with low- inal bit-rate, the data itself Tlimiting factor for today’s ap- er bit-rates. In passenger is transmitted with a high- plications. Each CAN frame it is used with a max- er bit-rate. The data bit-rate is acknowledged by the re- imum bit-rate of up to 800 only depends on the trans- ceiving nodes by sending kbit/s, while 500 kbit/s is mission characteristics and an acknowledgment flag more common. Commercial capabilities of the physi- into the transmitted frame. vehicles have larger topolo- cal layer, not on the sig- Thus the sender gets a di- gies, thus using up to 500 nal propagation delay. This rect in-frame response on kbit/s, but it is more com- concept provides backward successful message trans- mon to have 250 kbit/s. As compatibility with existing Dr. Tobias Lorenz mission. However, this re- applications become more CAN controllers. The sec- Etas GmbH quires that the propagation and more bandwidth-in- ond improvement is that a PO Box 300220 time for sending the phys- tense, CAN has to compete data frame can have up to DE-70442 ical signal to the most dis- with more modern technol- 64 bytes of payload. In ad- Tel.: +49-711-89661-0 tant node and back is not ogies such as Ethernet (bit- dition, the requirement for Fax: +49-711-89661-107 longer than the time frame rates above 100 Mbit/s over transport protocols can [email protected] for the acknowledgement a distance of 100 m). Be- be dropped in several use signal itself. The propaga- side the limited bit-rate, the cases. CAN FD also intro- Link tion delay is mainly imposed maximum data field length duces the CRCs (cyclic re- www.etas.com by the transceivers and the of 8 bytes is also insuffi- dundancy checks) for larg- cable length. Thus, there is cient for today’s applica- er frames, which take the Introduction a reciprocal relationship be- tions. Transport protocols CAN stuff bits into account. In 1987 Bosch introduced tween the bit-rate and the are necessary to transmit This ensures that the safety the Controller Area propagation delay. larger chunks of data. level remains constant with Network, which soon CAN was designed With CAN FD it is pos- a hamming distance of six. became one of the for a maximum bit-rate of sible to transmit a CAN Following are some of the most popular in-vehicle 1 Mbit/s on a cable with a frame with two different bit- use cases that directly ben- network technologies and maximum length of 40 m. rates. While the control data efit or even require CAN FD was used in many other Due to the emission limits (arbitration, acknowledge- communication. industries. Today CAN is still the most commonly used network in the automotive area, but the latest vehicle systems with high data rates require the introduction of CAN FD (CAN with flexible data rate) as its successor.

Figure 1: CAN FD provides a seamless upgrade path for CAN technology towards Flexray and Ethernet

28 CAN Newsletter 1/2013

Tools for CAN FD Etas already provides tools for CAN FD. During the CAN FD Tech Day in Detroit, modified versions of the FPGA- based ES593-D device and Busmaster were presented. The ES593-D is a member of the CAN FD-capable ES59x ECU and bus access module series also including ES592 and ES595. The ES910 rapid prototyping module supports CAN FD as well. The scalable ES8xx system with a power plate on the bottom and several modules stacked on the top, is scheduled Figure 2: The average CAN FD bit-rate benefits from payloads of up to 64 bytes for release in Q2/2014. The available modules Fast tocol layer. Further speed are possible, which results interconnected via a high- download increases are gained due in a 98-% net rate. speed communication to the reduced overhead network with low latency According to Moore’s Law, of the transport protocol. Time-synchronous will include the ES850 the complexity of integrat- A transport protocol usu- data transmission analog input module, ed circuits doubles every ally requires 1 byte for PID for one motion the ES820 computing 12 months. As stated by In- (Packet ID), and the 7 bytes controller module, and the ES890 tel executive David House, of DAQ (data acquisition ECU and bus interface the performance doubles in message), thus resulting in Real-time applications re- module. The latter will a period of 18 months. Sim- an 88-% net rate. With CAN quire a reliable time be- feature CAN, CAN FD, ilar numbers apply for the FD, up to 63-bytes DAQs havior. Mapped to network Flexray, ECU access, overall system complexi- and connectivity to ty and software size. This other company’s legacy has already led to the prob- hardware. lem that complete software Busmaster 1.7.0 free-to- downloads via the on-board use open-source solution diagnostic (OBDII) port to for network analysis and the vehicle ECUs take sev- simulation supports CAN eral hours. FD. It handles the second According to General bit-rate and frames with Motors [3] (similar numbers up to 64 bytes, each in apply for other OEMs as the message window, well), the CAN-based OB- and the node simulation. DII port is used with a nom- The tool is available since inal bit-rate of 500 kbit/s. November 2012 and can To have the maximum net Figure 3: With CAN FD about four times higher net band- be downloaded at http:// bit-rate, transmissions are width is realistic rbei-etas.github.com/ supposed to have 8 bytes busmaster. Inca is a of data. Thus the time CAN FD-capable tool for to transmit each frame is measurement, calibration, 1021 µs. and diagnostics. The With CAN FD, the support will be officially nominal bit-rate is kept at released with the market 500 kbit/s, but a data bit- introduction of the rate of 2 Mbit/s is used. In ES890. As of today, the addition, frames are trans- configuration formats mitted with 32 bytes of pay- and transport protocols load. Increased bit-rate and are not yet ready payload length leads to a for CAN FD. Further reduction in transmission standardization in

time to 229 µs (see Figure ASAM, ISO, and SAE CAN Improved 3). Thus, a four times high- is necessary to take full er net bandwidth can be Figure 4: Four PDOs are required to position a motion advantage of CAN FD. achieved solely on the pro- controller with classic CAN

CAN Newsletter 1/2013 33 References [1] Vector Congress, November 2012, Stuttgart, Germany, CAN FD – CAN with flexible data rate, Thomas Lindenkreuz, Figure 5: With CAN FD, one message is sufficient to position a motion controller Robert Bosch [2] CAN FD Tech Day Figure 6 in [1]). Thus CAN in Detroit, USA, FD is fit for the next gener- October 2012, ation of powertrain require- Improved CAN Improved CAN FD – CAN with ments. flexible data rate, Let’s assume all Florian Hartwich, frames are transmitted with Robert Bosch 8 bytes. Due to the control [3] CAN FD Tech Day information in the frame in Detroit, USA, header and trailer, and the October 2012, additional stuff bits, the data CAN FD requirements consumes between 40 % from the OEM and 58 % of the total frame. point of view, Using CAN FD and data Natalie Wienckowski, frames with 32 bytes, the ef- General Motors ficiency can be improved to [4] International between 64 % and 84 %. In CAN Conference in addition, if the nominal bit- Hambach Castle, rate stays at 500 kbit/s, and Germany, March 2012, a data bit-rate of 4 Mbit/s is Using CAN with flexible introduced, the combined data rate in CANopen average bit-rate is approxi- systems, Figure 6: Bit-rate requirements growth estimation for mately 1,41 Mbit/s. Both ac- Heinz-Jürgen Oertel, Port electrical vehicles tions result in a reduction [5] CAN FD Tech Day of network utilization from in Detroit, USA, technologies, this require- required for the complete 50 % to 11 %. There is no October 2012, ment results in a time-syn- transmission is reduced to need to add further CAN Safe-guarding of chronous transmission of 11 bytes, which is a 50-% networks to handle the uti- CAN FD for applications information. Due to the fact increase in efficiency. lization problem, but further in , that CAN is limited to a data ECUs can be added to ex- Marc Schreiner, field size of 8 bytes, more Higher bandwidth for isting CAN networks. Daimler AG information has to be trans- electric vehicles mitted in subsequent mes- Accelerated sages. To have a reliable Among the CAN-based sys- communication on time behavior, it has to be tems in a vehicle, the pow- long CAN lines ensured that there is no ertrain CAN has the high- delay or interruption of the est average utilization. This Articulated busses feature a transmission due to frames is mainly due to the commu- CAN network with a length with higher priority. An ex- nication between the motor of approximately 20 m. ample for such application control unit and the trans- Trucks have a frame length is a robot arm [4]. Each axle mission control unit. Com- of approximately 9 m. The in this arm is equipped with monly it is used with 500 electronics architecture of a motion controller imple- kbit/s and has a utilization trucks and busses is stan- menting the CANopen de- of 50 %. dardized in the SAE J1939 vice profile for drives and Especially when it specification. Part 11 and motion control (CiA 402). comes to electric/hybrid 14 both define the phys- For each motion control- vehicles, new powertrain ical layers with a bit-rate ler (axle) four PDOs (pro- concepts demand a much of 250 kbit/s and a maxi- cess data objects) have to higher bit-rate and utiliza- mum bus length of 40 m. In be transmitted with a to- tion. Motor control unit and the last years, several sys- tal of 23 bytes (see Fig- transmission control unit tems e.g. such ADAS sys- ure 4 in [4]). With the in- will be replaced by a vehicle tems (advanced driver as- creased CAN FD data field control unit, DC/DC inverter sistance systems) as lane size, there is only one CAN control unit, battery control departure warning, bird-eye FD frame necessary to po- unit, charger control unit, view, and brake assist, mi- sition one motion control- and range extender control grated from the passen- ler. Without further mea- unit. Estimations show that ger segment into the sures, a time-synchronous by 2025, the expected re- and trailer market. transmission of informa- quired bit-rate will exceed This trend demands high- tion is ensured. In addition, the abilities of CAN and re- er bandwidth than J1939 the total number of bytes quire at least CAN FD (see offers today. J1939-14 was

34 CAN Newsletter 1/2013 Newsletter_CiA-Newsletter 16.10.2012 14:04 Seite 10

CANopen® Products and Services

Figure 7: The nominal bit-rate of J1939 is 250 kbit/s. The introduction of CAN FD with a 4-Mbit/s data bit-rate would lead to an average bit-rate of 810 kbit/s.

ES592 ES593-D

ES595 ES910 ® Figure 8: The ES59x and ES9xx series are prepared CANopen Master/Slave protocol for CAN FD software for the development of embedded applications

Windows CANopen drivers enable quick implementation of PC-based control and test applications

Broad range of PC interfaces to fit your specific requirements Figure 9: ES8xx series with the ES890 ECU and bus interface module Tools for configuration, testing standardized to have a bit-rate of 4 Mbit/s, the and analyzing bit-rate of 500 kbit/s and in- average combined bit-rate creased the maximum bus would be 810 kbit/s. Thus, length to 56,4 m. With CAN the transfer capacity is Consultation, implementation FD it is possible to keep the increased to 324 %. nominal bit-rate constant, and development services and to increase the data bit-rate independent of the cable length. If CAN FD is used with a nominal bit-rate of 250 kbit/s and a data IXXAT Automation GmbH Leibnizstr. 15 · 88250 Weingarten Tel.: +49-(0)7 51 / 5 61 46-0 Your Partner for Communication Internet: www.ixxat.de