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MSP430FR6820: ADC calculations provide wrong results?

Expert 5920 points
Part Number: MSP430FR6820


we are working on a design with MSP430FR6820, now trying to measure accurate values of thermistor, but It doesn´t work. Replaced termistor with fix resistors to check if ADC is counting properly; unfortunately counted values didn´t match with measured values of the ADC.

We checked gain factor and offset information from manufacturer, then found those values in the memory of MCU and when calculated final values(value*gain +offset), it didn´t match too.

I attached document with our calculations.


Can you help to understand where is the issue?



  • In your register display, P9SEL0.4 is set to 1, but P9SEL1.4 is set to 0, which is function "N/A", whatever that means. [Ref Data Sheet (SLASE23E) Table 6-31]

    Try adding:

    > P9SEL1 |= BIT4;   // P9.4 as A12 per data sheet Table 6-31

  • Hi Bart,

    In addition to Bruce's suggestions (thanks, Bruce!) did you check:

    1. Your ADC reference voltage? Is it set to what you want it to be?

    2. The data format? This is the ADC12DF bit.

    3. The actual voltage going into the ADC input? You can use a multi-meter to probe the voltage going into the ADC to double check that the thermistor circuit is correct.



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