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CCS/MSP430F2013: Stop conversion or just stop interrupt?

Franz Peter Zantis
Intellectual 415 points

Part Number: MSP430F2013

Tool/software: Code Composer Studio

The SD16ADC (e.g.g. in the MSP430F2013) is a sigma-delta-ADC. This type of ADC is preferably for continues work. So from my understanding, it makes sense to use it in continuous mode and, if it is not needed,  just do deactivate the interrupt for this device  (  SD16CCTL0 &= ~SD16IE;  ) instead of stopping the conversion (SD16CCTL0 &= ~SD16SC;    ). Am I right?

Best regards

Franz Peter Zantis

  • 0
    Guru 320650 points
    It would be possible to do that, but then you're using more power. You have to decide yourself whether it is worth it.
  • 0 in reply to Clemens Ladisch
    Intellectual 415 points
    Thank you for your answer.
    Now I remember, that it is not possible to let the ADC run if the channels must be switched - pity. If I switch from A4+ to A1+ without stopping the ADC (SD16CCTL0 &= ~SD16SC;), the values from A4+ are wrong.
  • 0 in reply to Franz Peter Zantis
    Guru 46710 points

    Franz Peter Zantis said:
    If I switch from A4+ to A1+ without stopping the ADC (SD16CCTL0 &= ~SD16SC;), the values from A4+ are wrong.

    Only first (upto 4) values of SD ADC output after input switch are kinda wrong. To avoid digital filter settling "phenomena", you shall configure SD16INTDLYx (bits 7-6) to 00 which means "Fourth sample causes interrupt". Further reading: SLAU144J, 26.2.7 Digital Filter, 26.2.11.2 Interrupt Delay Operation.

    Regarding "stop conversion or stop interrupt" - I would drop samples (effectively the same as stop interrupt) if duty cycle of used:skipped ADC samples is <= 1:10. There' s another good way to slow SD ADC down: lower ADC clock frequency, thus lower sample rate. If I need just ocassional SD ADC measurements, then obviously I would shut down ADC - to conserve power.

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