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Last Post 12 Sep 2007 07:48 AM by  itooo@itooo.com
CAN bus baud rate
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itooo@itooo.com



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11 Sep 2007 10:05 AM
    Hi,

    Could someone set correctly the CAN baud rate on the Sharp LH75401 ?

    My setup is very simple, I would like to acheive, for example 50Kbps :
    - Baud Rate = System Clock / 2 / (BRP[5:0]+1) / <Tq per bit>

    Here are the parameters
    - System clock = 14745600 * 7 / 2 = 51609600 Hz
    - BRP[5:0] = 51
    - Bit setup : TSEG1 = 6, TSEG2 = 1 -> 1 Sync Tq + 7 Seg1 Tq + 2 Seg2 Tq = 10 Tq per bit

    Resulting Speed should be ~49 624 bps... but my oscilloscope shows 66 666 bps (and it is not posessed by the devil, promise )

    Where did I fail in my formula ?

    Thank you

    kurtl@logicpd.com



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    11 Sep 2007 01:35 PM
    The schematics show 14.7456Mhz for the CPU crystal, however, the CPU and BOM were upgraded a few years back so they can run faster.

    The current BOM on the website shows a 20Mhz clock input to the CPU. That is probably the source of your calculations problem.

    -K

    itooo@itooo.com



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    12 Sep 2007 07:48 AM
    Thank you very much, this solved the problem, I had old documents.
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