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Thread: SPI bus and wire length?

  1. #1

    Default SPI bus and wire length?

    How long can the wire connections be on a SPI bus? The reason I am
    asking this is I want to interface to a MAX6674 from Maxim to a BS2
    40P that is going to be 6 feet away or more with shielded, twisted
    pair cable. Will this work or am I pushing this technology? Should I
    use series termination on the SPI bus to slow the edges down to
    minimize overshoot/undershoot? The MAX 6674 is going to be located as
    close to the thermocouple as possible to improve it's accuracy.

    Jason
    Last edited by ForumTools; 10-01-2010 at 11:33 PM. Reason: Forum Migration

  2. #2

    Default

    Jason,

    Since you are doing SPI with 6674 (I need to do the same in a near
    future) can you recommend a good explanation of SPI? In my case it
    should be simple two slaves (6674, and a DAC) single master project.
    Neither Scott's book, no Al's give any details. I looked at MAXIM
    site and have not found much either. Sorry to bother you.

    Thanks a million.

    Alex.


    --- In basicstamps@y..., "jbirnsch" <jbirnsch@v...> wrote:
    > How long can the wire connections be on a SPI bus? The reason I am
    > asking this is I want to interface to a MAX6674 from Maxim to a BS2
    > 40P that is going to be 6 feet away or more with shielded, twisted
    > pair cable. Will this work or am I pushing this technology? Should
    I
    > use series termination on the SPI bus to slow the edges down to
    > minimize overshoot/undershoot? The MAX 6674 is going to be located
    as
    > close to the thermocouple as possible to improve it's accuracy.
    >
    > Jason
    Last edited by ForumTools; 10-01-2010 at 11:33 PM. Reason: Forum Migration

  3. #3

    Default

    SPI aka Microwire aka 3/4 wire bus. Consists of a serial data in line , serial
    data out
    line(may only have 1 of these), a clock line and a chip select. Not sure of the
    maximum clock speed. On the STAMP you use the Shiftin/out
    command(data,clock) along with chip select on an i/o pin.
    Motorola site should have specs.

    >
    > Since you are doing SPI with 6674 (I need to do the same in a near
    > future) can you recommend a good explanation of SPI?
    Last edited by ForumTools; 10-01-2010 at 11:33 PM. Reason: Forum Migration

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