Having trouble with SERIN command and MAX6675


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  1. #1
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    If you have an O-scope check the data out pin. That will at least let you know if it's responding.
    Regards,

    -Bruce
    tech at rentron.com
    http://www.rentron.com

  2. #2
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    Quote Originally Posted by Bruce View Post
    If you have an O-scope check the data out pin. That will at least let you know if it's responding.
    the O-scope test checked out alright

  3. #3
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    I just disabled the comparators in the chip but it still won't. I even replaced the thermocouple and the MAX76675 but i get the same response. I have no idea what could be wrong with this. Any ideas?
    Last edited by emerson; - 10th December 2010 at 17:44.

  4. #4
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    Have you tried sending the raw value received 'without modifying it' to your LCD while heating or cooling the part?

    Something like: lcdout $fe, $c0, BIN16 MXtemp

    Does it change when heated?

    Edit: Since you're using the internal osc on this one, place Define OSCCAL_1K 1 in the top section. Not sure it that will fix it, but it will for sure affect timing.
    Last edited by Bruce; - 10th December 2010 at 17:48. Reason: Define OSCCAL_1K 1
    Regards,

    -Bruce
    tech at rentron.com
    http://www.rentron.com

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    Quote Originally Posted by Bruce View Post
    Have you tried sending the raw value received 'without modifying it' to your LCD while heating or cooling the part?

    Something like: lcdout $fe, $c0, BIN16 MXtemp

    Does it change when heated?

    Edit: Since you're using the internal osc on this one, place Define OSCCAL_1K 1 in the top section. Not sure it that will fix it, but it will for sure affect timing.
    I just tried it and there is no change

  6. #6
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    What's the 16-bit value shown?
    Regards,

    -Bruce
    tech at rentron.com
    http://www.rentron.com

  7. #7
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    Quote Originally Posted by Bruce View Post
    What's the 16-bit value shown?
    0000 0000 0000 0000

    zeros across the board with no change to heat

  8. #8
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    Is the thermocouple a K type?
    The code given in the link I gave works.
    Check the hardware. Bad connections or backwards connection on the thermocouple or wrong type will cause problems.
    Dave
    Always wear safety glasses while programming.

  9. #9
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    Did you look at the data output pin on the MAX chip with your O-scope to see if it's changing the value sent?

    If you send 16 clocks, and the data line stays at ground, I would think there's a problem with the MAX IC. If you see transitions on the data line, there's something going on with the PIC side.
    Last edited by Bruce; - 10th December 2010 at 19:30.
    Regards,

    -Bruce
    tech at rentron.com
    http://www.rentron.com

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