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Converting only a specific part to digital in a ADC code for sine wave

Yashaswy Akella
Expert 1070 points
Other Parts Discussed in Thread: MSP430FR5969

I was exploring about the ADC in the MSP430FR5969.Is is possible to convert only a specific part in a sine wave and get a digital output apart from converting the entire wave?

  • 0
    Guru 318740 points

    How are you going to know which part you're in before you have measured something?

    But if you are sure about your timing, you can stop and restart the ADC.

  • 0 in reply to Clemens Ladisch
    Guru 11940 points

    How are you going to know which part you're in before you have measured something?

    By detecting the zero-crossings of the input signal. But that would require additional analogue input hardware and the knowledge of the frequencies involved, and probably defeat the purpose of using the ADC of an MCU in the first place.

    Stated differently, it is useful only for known signals like mains (240V/50Hz or 120V/60Hz).

  • 0 in reply to f. m.
    Guru 46710 points

    If you are interested in part(s) of continuous (pure) sine wave, then best approach would be just continuous sampling, analyzing ADC data and dropping unneeded samples. Any other approach like starting conversions from external circuit can introduce lag which could be nondeterministic, especially if interrupts are involved, not to mention possibility of noise causign false triggers.

  • 0 in reply to Ilmars
    Guru 11940 points
    You are correct.
    But I "decoded" the OP's question as if he wants to avoid exactly that.

    ... not to mention possibility of noise causign false triggers.

    In case of the ZXD for mains voltages, this were mostly EMI problems, which finally had an impact on both hardware and software ...

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