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MSP430FR2676: Using TLV ADC Gain Calibration values

JD Scott1
Prodigy 40 points

Part Number: MSP430FR2676
Other Parts Discussed in Thread: CAPTIVATE-FR2676

I'm attempting to calculate a gain-corrected ADC value using the MSP430FR2676. The User's Guide outlines the following calculations:

The datasheet indicates the Gain factor is in memory location 0x1A16. The value read at that address for my specific part (a CAPTIVATE-FR2676 development board) is 16357. When I perform the calculations as described with an assumed ADC reading of 2048 (mid-range at 12-bit resolution), the result is 0.12520633367977 which is not correct. The calculation as performed is detailed below:

The data type of the gain value is not explicitly defined, though it is for the offset error correction value. However, I cannot see how a data type difference would improve the situation.

What is it that I'm missing? Any help would be very much appreciated.

Thanks,

JD Scott

  • 0
    Prodigy 40 points

    It occurs to me that the MCU on this development board is actually an XFR2676. Is it possible that this experimental MCU does not have a valid gain factor? We have prototype boards for this product coming in a couple weeks and I can re-test then, but some confirmation here would put my mind at ease.

    Thanks again,

    JD

  • 0 in reply to JD Scott1
    TI__Mastermind 47375 points

    Hi JD,

    Yes, it is possible that the X silicon does not have valid gain factor programmed.  I don't have specific information on this device, but full device parameters are not guaranteed on the X silicon.  I would recommend testing with the proto boards you have coming and let us know if you see something similar.  Another option could be to order a couple sample ICs, which you can get in a couple days, and populate on the development board if you have the capability to solder a new device.    

  • 0 in reply to Eddie LaCost
    Prodigy 40 points

    Hi Eddie,

    Thanks for the response. There may be a couple issues related to the experimental XFR2676, including the on-chip temperature sensor. I'll post my findings here when the board is assembled and tested.

    Thanks again,

    JD

  • 0 in reply to JD Scott1
    TI__Mastermind 47375 points

    Sounds good.  Thanks!

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