Sampling ADC with two sampling frequency alternately....

RE: Sampling ADC with two sampling frequency alternately....

Ankush — Mon, 26 Sep 2016 11:30:49 GMT

Ok Ole. Thanks for your support.

RE: Sampling ADC with two sampling frequency alternately....

Ole Bauck — Mon, 26 Sep 2016 11:22:30 GMT

My colleague Stefan is working on this case so he will assist you.

RE: Sampling ADC with two sampling frequency alternately....

Ankush — Mon, 26 Sep 2016 11:12:24 GMT

Yes Sure I will test it. Thanks.

Can you help to resolve one more issue written in following thread? devzone.nordicsemi.com/.../.

RE: Sampling ADC with two sampling frequency alternately....

Ole Bauck — Mon, 26 Sep 2016 10:28:22 GMT

The uninit looks fine to me, but be sure to test it.

RE: Sampling ADC with two sampling frequency alternately....

Ankush — Mon, 26 Sep 2016 10:00:35 GMT

Hi Ole,

Thanks for your reply. This what I wanted. Right now I am trying to use following uninitialized function, which giving me the desired results. This is the function that I am using-->

    void saadc_sampling_event_uninit(void)
{
    ret_code_t err_code;

    err_code = nrf_drv_ppi_channel_free(m_ppi_channel);
    APP_ERROR_CHECK(err_code);

    nrf_drv_timer_disable(&m_timer);

    nrf_drv_timer_uninit(&m_timer);

    nrf_drv_ppi_uninit();
}

Is this wright?

But I will try to use new approach specified by you. Thanks once again for your answer.

RE: Sampling ADC with two sampling frequency alternately....

Ole Bauck — Mon, 26 Sep 2016 08:52:43 GMT

Calling saadc_sampling_event_init() multiple times will not work. Every time you call saadc_sampling_event_init() you will try to initialize ppi and timer module again which will return an error code, which will make the application stop because of APP_ERROR_CHECK(err_code). Even if you fix this you will also allocate new PPI channel every time, and eventually you will run out of PPI channels. So don't call saadc_sampling_event_init() multiple times (unless you implement a proper uninit function).

What you can do is to change the compare value of the timer with the nrf_drv_timer_extended_compare(..) function. Be aware though that if you don't stop and clear the timer first, the timer may miss the compare event (the current value of the timer may be larger than the new compare value) and count until it overflows. You can avoid this by updating with stop, clear and resume like this (sets the compare value to 400ms or 2.5Hz):

nrf_drv_timer_pause(&timer);
nrf_drv_timer_extended_compare(&timer, (nrf_timer_cc_channel_t)0, 400 * 1000UL, NRF_TIMER_SHORT_COMPARE0_CLEAR_MASK, false);
nrf_drv_timer_clear(&timer);
nrf_drv_timer_resume(&timer);

Or you can do it with disable and enable:

nrf_drv_timer_disable(&timer);
nrf_drv_timer_extended_compare(&timer, (nrf_timer_cc_channel_t)0, 400 * 1000UL, NRF_TIMER_SHORT_COMPARE0_CLEAR_MASK, false);
nrf_drv_timer_enable(&timer);