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paul2
paul2
Associate III
July 8, 2014
Question

STM32F4 - trigger digital output based on ADC - minimizing delays

  • July 8, 2014
  • 3 replies
  • 907 views
Posted on July 08, 2014 at 09:30

Hi,

I’m trying to minimize control loop delays. Based on a certain analog value (adjustable threshold) a digital output is triggered. Reading ADC values is done by using DMA, digital outputs are driven without DMA.

Results measured by scoop: minimum delay ~300 μs, variation ~90 μs (min

300 μs,

max

390 μs

)

Does anybody have some tips/tricks/best practices minimizing ADC-DO control loop delays?

Thanks.

    This topic has been closed for replies.

    3 replies

    chen
    chen
    Associate II
    July 8, 2014
    Posted on July 08, 2014 at 10:26

    Hi

    ''

    I’m trying to minimize control loop delays. Based on a certain analog value (adjustable threshold) a digital output is triggered. Reading ADC values is done by using DMA, digital outputs are driven without DMA.

    ''

    ''

    Does anybody have some tips/tricks/best practices minimizing ADC-DO control loop delays?

    ''

    Not sure what you mean by 'ADC control loop' ??

    Try looking at the 'Analogue Watchdog' feature of the ADC.

    It is basically 2 threshold values which can trigger an IRQ

    frankmeyer9
    frankmeyer9
    Associate III
    July 8, 2014
    Posted on July 08, 2014 at 11:21

    Why not using a discrete comparator, or a stm32f3 with integrated comparators ?

    That would remove much software-induced delays from the loop.

    For better suggestions, you might perhaps reveal more details about your application.

    Tesla DeLorean
    Tesla DeLorean
    Guru
    July 8, 2014
    Posted on July 08, 2014 at 13:22

    A singular ADC value, how frequently? Perhaps you could avoid DMA, or use an alternate ADCx unit, and use the EOC interrupt to read/process the threshold

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