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CAN FD demonstrator

With 20 nodes at a 40-m network

Texas Instruments (TI) has developed a CAN FD kit to demonstrate its 5-Mbit/s transceiver chips. The linear network topology features varying stubs with up to 2 m.

Linear topology with stubs: The total terminated trunk length is 40 m with 30 to 37 twists per meter (Photo: Texas Instruments)

The U.S. chipmaker showed its CAN FD demonstrator for the first time at the Electronica fair 2016 and then in Las Vegas at the CES 2017. The nodes implement the MCAN module from Bosch and are equipped with TCAN1042 and TCAN1051 transceiver chips from TI. They comply with ISO 11898-2:2016 and support bit-rates up to 5 Mbit/s. The chips are available in 8-pin SOIC and 8-pin (3x3) VSON enclosures.

The demonstrator could be used to learn more about CAN FD topologies – especially to stress the network components in terms of busload, timing, temperature, data-rates. The 40-m cable is made of AWG22 wires, which are specified for temperatures up to 125 °C. The twisted-pair cable has 30 to 37 twists per meter. At the used 9-pin D-sub connectors the maximum untwisted length is 50 mm to 60 mm.

The first implementation uses eight boards with two CAN FD channels each. The entire network provides 20 connectors. In all nodes a clock frequency of 40 MHz, one of the frequencies recommended by CiA. The bit-timings are set in a way that there equal time-quanta length in the nominal (arbitration) and the data (dataphase) bit-rate. The sample-point is of course the very same in all nodes. The TDC (transceiver delay compensation) was enabled as recommended in CiA 601-2.

In order to demonstrate system durability and robustness, the demonstrator was running at 2 Mbit/s for an extended period in time, in which more than 12 million messages were transacted without a single-bit error. The similar test has been performed running at 5 Mbit/s. It was not just a point-to-point communication. In the next evaluation tests, the environment will be heated and cooled. Additionally, TI will continue to monitor statistics in software and to study effects of changes in cable characteristics.