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TMP117 I2C

Other Parts Discussed in Thread: TMP117

There is no checksum in the TMP117 communication. How to make sure that the temperature is read correctly?

  • Hi Boris,

    Welcome to the E2E forums and thank you for your post.

    You're correct that the TMP117 does not provide a checksum for verifying the read results. 

    We haven't seen a need for this in most TMP117 applications, but if you are looking for some greater reliability in your results you could always read the temperature register multiple times after a conversion. The same data set will remain available until overwritten by the next temperature conversion. 

    Please let me know if you have any other questions or concerns.

    Best Regards,
    Brandon Fisher

  • Hi Brandon,
    Thanks. I'm going to try.
    This is very important, because I read  the wrong temperature, sometimes.
    Best Regards,
    Boris Belov



    13.09.2019 18:46, Brandon Fisher94 пишет:

     

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    RE: TMP117 I2C

    Brandon Fisher94

    Hi Boris,

    Welcome to the E2E forums and thank you for your post.

    You're correct that the TMP117 does not provide a checksum for verifying the read results. 

    We haven't seen a need for this in most TMP117 applications, but if you are looking for some greater reliability in your results you could always read the temperature register multiple times after a conversion. The same data set will remain available until overwritten by the next temperature conversion. 

    Please let me know if you have any other questions or concerns.

    Best Regards,
    Brandon Fisher



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  • Hi Boris,

    Is this a communication error you are seeing or are you seeing invalid values?

    If possible, can you capture one of your I2C read transactions on an oscilloscope to share?

    Best Regards,
    Brandon Fisher

  • Hi Brandon,
    I see invalid values. I see it very rarely. What length of TMP117 communication line is allowed ? I'm using 3.3 V power.
    I added extra reading data and data comparison.
    Best regards,
    Boris Belov

    17.09.2019 15:34, Brandon Fisher94 пишет:

     

    A Message from the TI E2E™ support forums

     

    Brandon Fisher94 replied to TMP117 I2C.

    Hi Boris,

    Is this a communication error you are seeing or are you seeing invalid values?

    If possible, can you capture one of your I2C read transactions on an oscilloscope to share?

    Best Regards,
    Brandon Fisher

     

     

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  • Hi Boris,

    I can't seem any images you attach when replying via email. You may have to visit this thread directly on the E2E forums and attach them there.

    The limiting factor in communication distance for I2C is typically bus capacitance. In standard mode this limit is generally given as around 400pF, in fast mode it is closer to 200pF. This generally translates to a distance of a few meters. 

    Reducing your communication frequency is the first step I would take if looking to use I2C over a longer distance. 

    Best Regards,
    Brandon Fisher

  • Hi Boris,

    Do you still need assistance? Could you please review Brandon's questions and update us?

    Thanks,

    Ren