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sampling through timer

Discussion in 'Electronic Design' started by jackbauer, May 16, 2007.

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  1. jackbauer

    jackbauer Guest


    I'm using microC/OS on MSP430F1611 and have used semaphores in all of
    my SPI functions. Both the spi Tx and Rx use DMA.

    I have an 8 channel external ADC and I want to sample my channels at
    some rate using interrupt and Timer B. But I can't request a semaphore
    in ISR.... So I was wondering if anyone has a good idea of
    implementing a stable sample rate on an external ADC while using
    microC/OS tasks (I don't need to use timers if there is a more
    efficient method.)

    Thanks a lot.
  2. Tim Wescott

    Tim Wescott Guest

    The best way to do that is drive the ADC's start-conversion pin from the
    timer output pin, and drive an external interrupt from the ADC's
    end-of-conversion pin. That way you're controlling the sampling with a
    hardware timer.


    Tim Wescott
    Wescott Design Services

    Posting from Google? See

    Do you need to implement control loops in software?
    "Applied Control Theory for Embedded Systems" gives you just what it says.
    See details at
  3. jackbauer

    jackbauer Guest

    I'm using ADS8345 which triggers a conversion whenever SPI receives
    one byte. So to sample a channel, I write a byte to SPI. So I'm not
    sure how to implement your method... Please advise
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