PPI with multiple SAADCs and multiple TIMERs

RE: PPI with multiple SAADCs and multiple TIMERs

Duy — Mon, 15 Jul 2019 15:15:59 GMT

Hello Håkon Alseth,

One more question, which function or variable allows me to know that the sample belongs to SAADC channel 0, 1, 2...?

Thank you and best regards,

Duy

RE: PPI with multiple SAADCs and multiple TIMERs

Duy — Mon, 15 Jul 2019 09:38:56 GMT

Hello,

Thank you for your feedback. Now I understand. So all I need is only 1 PPI channel, is it right? It will trigger both SAADC channels too.

I also found the answer for similar question about multiple SAADCs at different intervals: https://devzone.nordicsemi.com/f/nordic-q-a/20214/multiple-saadc

RE: PPI with multiple SAADCs and multiple TIMERs

Håkon Alseth — Mon, 15 Jul 2019 08:24:59 GMT

Hi,

I am very sorry, I have misinformed you previously.

When you are enabling more than one channel, the SAADC enters scan mode, where it samples all enabled channels when you trigger the start task.

Due to this behavior in hardware, you are actually sampling both inputs at 5 ms interval.

Kind regards,

Håkon

RE: PPI with multiple SAADCs and multiple TIMERs

Duy — Fri, 12 Jul 2019 15:36:57 GMT

Hello Håkon Alseth,

Please have a look at my code in main.c and my configuration is sdk_config.h file. Sorry for make it not clear but I still don't get it work. I enabled TIMER1 and TIMER2.

The TRANSDUCER_TIMER is TIMER1 and BATTERY_TIMER is TIMER2. I think I have to clear a register to get this to work.

const nrf_drv_timer_t TRANSDUCER_TIMER = NRF_DRV_TIMER_INSTANCE(1);                 /**< ADC timer. */
const nrf_drv_timer_t BATTERY_TIMER = NRF_DRV_TIMER_INSTANCE(2);                    /**< Battery timer. */

Thank you and best regards,

Duy
devzone.nordicsemi.com/.../55478.main.c devzone.nordicsemi.com/.../0601.sdk_5F00_config.h

RE: PPI with multiple SAADCs and multiple TIMERs

Håkon Alseth — Fri, 12 Jul 2019 11:00:33 GMT

Hi Duy,

[quote user="DuyLionTran"]Thank you for your answer, I am running 2 different timers running in different periods (10ms and 5s). If I run only 1 ADC channel + 1 TIMER with PPI, everything works fine.[/quote]

Yes, that is expected to work. In your initial code, you are using one timer (with 2 capture/compare events), which will cause the timer to clear itself on the last event, thus you end up in a scenario where it runs the first SAADC task after 5 ms, and the next one after 4.995 seconds, before the timer itself is cleared.

If you add another timer instance to your application, it should work with 2 SAADC channels + 2 TIMERs.

Kind regards,

Håkon

RE: PPI with multiple SAADCs and multiple TIMERs

Duy — Fri, 12 Jul 2019 08:16:05 GMT

Hello Håkon Alseth,

Thank you for your answer, I am running 2 different timers running in different periods (10ms and 5s). If I run only 1 ADC channel + 1 TIMER with PPI, everything works fine.

Warm regards,

Duy

#define APP_ADV_INTERVAL                32                                          /**< The advertising interval (in units of 0.625 ms. This value corresponds to 25 ms). */
#define ADC_ACQUISITION_INTERVAL        10          
#define BATTERY_LEVEL_MEAS_INTERVAL     10000                                       /**< Battery level measurement interval (ticks). */

#define APP_ADV_DURATION                18000                                       /**< The advertising duration (180 seconds) in units of 10 milliseconds. */

static void saadc_init(void)
{
    nrf_saadc_channel_config_t adc_channel_config = NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN1);
    nrf_saadc_channel_config_t battery_channel_config = NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN2);

    APP_ERROR_CHECK(nrf_drv_saadc_init(NULL, saadc_transducer_callback));
//    APP_ERROR_CHECK(nrf_drv_saadc_init(NULL, saadc_battery_callback));

    APP_ERROR_CHECK(nrf_drv_saadc_channel_init(0, &adc_channel_config));
    APP_ERROR_CHECK(nrf_drv_saadc_channel_init(1, &battery_channel_config));

    APP_ERROR_CHECK(nrf_drv_saadc_buffer_convert(m_buffer_pool[0], RAW_ADC_BUFF_SIZE));
    APP_ERROR_CHECK(nrf_drv_saadc_buffer_convert(m_buffer_pool[1], RAW_ADC_BUFF_SIZE));
}


/**@brief Function for the Timer initialization.
 *
 * @details Initializes the timer module. This creates and starts application timers.
 */
static void timers_init(void)
{
    nrf_drv_timer_config_t timer_cfg = NRF_DRV_TIMER_DEFAULT_CONFIG;

    /* Enable app timer */
    APP_ERROR_CHECK(app_timer_init());

    /* Create ADC timer */
    APP_ERROR_CHECK(nrf_drv_timer_init(&TRANSDUCER_TIMER, &timer_cfg, adc_acquisition_timeout_handler));
    nrf_drv_timer_extended_compare(&TRANSDUCER_TIMER, NRF_TIMER_CC_CHANNEL0, nrf_drv_timer_ms_to_ticks(&TRANSDUCER_TIMER, ADC_ACQUISITION_INTERVAL), NRF_TIMER_SHORT_COMPARE0_CLEAR_MASK, true);

    /* Configure BATTERY TIMER */
    APP_ERROR_CHECK(nrf_drv_timer_init(&BATTERY_TIMER, &timer_cfg, battery_level_meas_timeout_handler));
    nrf_drv_timer_extended_compare(&BATTERY_TIMER, NRF_TIMER_CC_CHANNEL0, nrf_drv_timer_ms_to_ticks(&BATTERY_TIMER, BATTERY_LEVEL_MEAS_INTERVAL), NRF_TIMER_SHORT_COMPARE0_CLEAR_MASK, true);
}


static void saadc_sampling_event_init(void)
{
    uint32_t transducer_timer_compare_event_addr, battery_timer_compare_event_addr;
    uint32_t saadc_sample_task_addr;

    APP_ERROR_CHECK(nrf_drv_ppi_init());

    nrf_drv_timer_enable(&TRANSDUCER_TIMER);
    nrf_drv_timer_enable(&BATTERY_TIMER);

    transducer_timer_compare_event_addr = nrf_drv_timer_compare_event_address_get(&TRANSDUCER_TIMER, NRF_TIMER_CC_CHANNEL0);
    battery_timer_compare_event_addr = nrf_drv_timer_compare_event_address_get(&BATTERY_TIMER, NRF_TIMER_CC_CHANNEL0);
    
    saadc_sample_task_addr = nrf_drv_saadc_sample_task_get();
    /* Setup ppi channel so that timer compare event is triggering sample tasks in SAADC */
    APP_ERROR_CHECK(nrf_drv_ppi_channel_alloc(&TORQUE_SAADC_TIMER_PPI_CHANNEL));
    APP_ERROR_CHECK(nrf_drv_ppi_channel_alloc(&BATTERY_SAADC_TIMER_PPI_CHANNEL));

    APP_ERROR_CHECK(nrf_drv_ppi_channel_assign(TORQUE_SAADC_TIMER_PPI_CHANNEL, transducer_timer_compare_event_addr, saadc_sample_task_addr));
    APP_ERROR_CHECK(nrf_drv_ppi_channel_assign(BATTERY_SAADC_TIMER_PPI_CHANNEL, battery_timer_compare_event_addr, saadc_sample_task_addr));
}

RE: PPI with multiple SAADCs and multiple TIMERs

Håkon Alseth — Fri, 12 Jul 2019 07:35:24 GMT

Hi,

If you want one SAADC channel to run every 5ms, and another to run every 5 seconds, you need to use two timers.

This is because the timer itself will not count to 5 ms, fire the event for sampling your first channel, then run for another 4.995 seconds before triggering the event to sample your second channel.

Could you try to run a individual timer per event and see if that works better?

Kind regards,

Håkon