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F28335 ECan Speet 1 MBit/s

Tom15617
Prodigy 120 points

Normal 0 21 false false false DE X-NONE X-NONE MicrosoftInternetExplorer4 I have som trouble to configure the eCan speed to 1 MBit.

When I configure the Can Bus with the TI ECan initialization file to 500 kBit/s, the can bus work fine. But when I change the speed by changing the BRPREG from 9 to 4, the Can dosen´t work

ECanaShadow.CANBTC.bit.BRPREG = 4;            // 500kBit/s=9 // 1MBit/s=4
ECanaShadow.CANBTC.bit.TSEG2REG = 2;
ECanaShadow.CANBTC.bit.TSEG1REG = 10;


Do I have to change also TSEG1REG and TSEG2REG?

Thanks

Tom

  • 0
    Mastermind 7585 points

    The setup from above (4,2,10) is correct to get a CAN - speed of 1 Mbit/s for a 28335 running at 150MHz PLL speed. I use this setup frequently in my projects. So it must be something different...

    Have you checked your bit timing at 500 kbit/s with a scope? Just to make sure that the clock system of the DSP is running as expected and that you actually see the 2 microseconds for a CAN bit period.

    If the timing is correct at 500 kbit/s, then you will have to give us a little bit more information about what's exactly not working at 1 Mbit/s.  The EMC situation at 1 Mbit/s is different from the one at 500 kbit/s. The system becomes more susceptible for incorrect line termination, overall line length, open stubs etc. It is quite common that a physical CAN with a non optimal physical setup works well at lower speeds (because there is enough time for line settlement) but when you increase the speed it doesn't work anymore.

    Regards