Timer 2 Capture at Low Frequency Input

RE: Timer 2 Capture at Low Frequency Input

inspiringdev123 — Wed, 19 Jul 2023 18:08:42 GMT

I have it set up as follows to stop the first timer after 100ms and capture the value of the second timer (pulse counter). The CC value is always 0 and is not recording the pulses now.

//setup a timer for Speedo/Tach pulses
    nrf_drv_timer_config_t timer_cfg2 = NRF_DRV_TIMER_DEFAULT_CONFIG; //default settings should use NRF_TIMER_FREQ_8MHz, changable in sdk_config.h
    timer_cfg2.frequency = NRF_TIMER_FREQ_62500Hz;
    timer_cfg2.bit_width = NRF_TIMER_BIT_WIDTH_16;
    timer_cfg2.interrupt_priority = APP_IRQ_PRIORITY_HIGH;

    err_code = nrf_drv_timer_init(&system_timer_cc_0_2, &timer_cfg2, system_timer_cc_0_2_handler);
    APP_ERROR_CHECK(err_code);

    //set up timer compare on CC[1] for 100ms interval on Timer 2
    nrf_drv_timer_extended_compare(&system_timer_cc_0_2, NRF_TIMER_CC_CHANNEL1, PULSE_READ_INTERVAL, NRF_TIMER_SHORT_COMPARE1_CLEAR_MASK, true);

    //setup a counter for Speedo/Tach pulses
    nrf_drv_timer_config_t timer_cfg3 = NRF_DRV_TIMER_DEFAULT_CONFIG; //default settings should use NRF_TIMER_FREQ_8MHz, changable in sdk_config.h
    timer_cfg3.bit_width = NRF_TIMER_BIT_WIDTH_32;
    timer_cfg3.mode = NRF_TIMER_MODE_LOW_POWER_COUNTER;
    timer_cfg3.interrupt_priority = APP_IRQ_PRIORITY_HIGH;

    err_code = nrf_drv_timer_init(&system_timer_cc_0_3, &timer_cfg3, system_timer_cc_0_3_handler);
    APP_ERROR_CHECK(err_code);

void system_timer_cc_0_3_init(void)
{
    uint32_t capture_task_addr;
    uint32_t compare_evt_addr;
    uint32_t gpiote_task_addr;
    uint32_t time_ticks;
    ret_code_t err_code;
    nrf_drv_gpiote_in_config_t in_config;

    /* CC[2]
     * Setup PPI tasks for GPIOTE and system timer channel[2]
     * for speedo/tach
    */

    //VCE: The below block needs to be called for each pin
    in_config.pull = NRF_GPIO_PIN_PULLDOWN; //User defined
    in_config.sense = NRF_GPIOTE_POLARITY_LOTOHI; //User defined
    in_config.hi_accuracy = true; //User defined
    in_config.is_watcher = false; //Don't change this
    in_config.skip_gpio_setup = false; //Don't change this

    //enable the pin for GPIOTE
    err_code = nrf_drv_gpiote_in_init(SPEEDO_TACHO_PIN_NUMBER, &in_config, speedo_tach_input_handler);
    APP_ERROR_CHECK(err_code);
    
    //setup a ppi channel to associate with the system_timer_cc_0_3 capture events
    err_code = nrf_drv_ppi_channel_alloc(&(ppi_channel[2]));
    APP_ERROR_CHECK(err_code);

    capture_task_addr = nrf_drv_timer_event_address_get(&system_timer_cc_0_3, NRF_TIMER_TASK_CAPTURE2);
    nrfx_gpiote_init(); 
    gpiote_task_addr = nrf_drv_gpiote_in_event_addr_get(SPEEDO_TACHO_PIN_NUMBER);

    err_code = nrf_drv_ppi_channel_assign(ppi_channel[2],  gpiote_task_addr, capture_task_addr);
    APP_ERROR_CHECK(err_code);

    err_code = nrf_drv_ppi_channel_enable(ppi_channel[2]);
    APP_ERROR_CHECK(err_code);
    
    nrf_drv_gpiote_in_event_enable(SPEEDO_TACHO_PIN_NUMBER, true);

    //Once all system_timer_cc_0_3 shared peripherals are ready, enable the shared timer
    nrf_drv_timer_enable(&system_timer_cc_0_3);

}

void system_timer_cc_0_2_handler (nrf_timer_event_t event_type, void * p_context)
{
    volatile uint32_t pulseCount;
    switch(event_type)
    {
        case NRF_TIMER_EVENT_COMPARE1:                    // call when timer 2 overflows
            NRF_TIMER3->TASKS_CAPTURE[2] = 1;             // This is asking to capture the current counter into CC[2]
            pulseCount = NRF_TIMER3->CC[2];               // counter value  at the instant when capture task was triggered is now ready to be read in CC[2]
            period = (uint32_t) ((1.0 / (float)pulses) * 100000);
            timerSetCC1(PULSE_READ_INTERVAL);
            pulses = 0;
            break;
            
        default:
            break;
    }
}

RE: Timer 2 Capture at Low Frequency Input

Kenneth — Tue, 18 Jul 2023 14:36:54 GMT

Both can work, but my suggestion was the second one.

Kenneth

RE: Timer 2 Capture at Low Frequency Input

inspiringdev123 — Tue, 18 Jul 2023 13:40:30 GMT

Are you saying to set up Timer2 as a counter and use the app timer to check every 10ms? Or set up Timer 2 as a counter and then set up another hardware timer to check?

RE: Timer 2 Capture at Low Frequency Input

Kenneth — Tue, 18 Jul 2023 08:19:48 GMT

I unfortunately don't have time to try out your code, but an alternative you may consider is to connect&use the pin as a counter for e.g. timer4, and then you only instead peridically check the counter value of timer4 from another timer (running of 16MHz clock, e.g. every 10ms) to find how many counts have elasped during the 10ms period.

Kenneth

RE: Timer 2 Capture at Low Frequency Input

inspiringdev123 — Mon, 17 Jul 2023 16:02:45 GMT

Yes that is true. The issue starts to occur around 50 Hz and below. There is a single jumpy reading causing the RPM's to spike, but then it recovers and stays consistent.

RE: Timer 2 Capture at Low Frequency Input

Kenneth — Mon, 17 Jul 2023 16:01:01 GMT

And, just so I don't misunderstand anything, you say that 10Hz is problematic while 100Hz is okey?

Kenneth

RE: Timer 2 Capture at Low Frequency Input

Kenneth — Mon, 17 Jul 2023 15:59:11 GMT

Can you just make a test code that continously read the input and write it on a different pin in a while loop? Just to see if that reveal anything?

Kenneth

RE: Timer 2 Capture at Low Frequency Input

inspiringdev123 — Mon, 17 Jul 2023 15:17:34 GMT

Did both to no avail

RE: Timer 2 Capture at Low Frequency Input

Kenneth — Mon, 17 Jul 2023 15:00:43 GMT

Hello,

I must admit I didn't look much at the code, but can you try to change the PRESCALER value and check if the threshold moves with the PRESCALER value?

Alternatively can you try to use 32-bit timer instead of 16-bit timer? See BITMODE register.

Kenneth