NRF5 SDK Timer HAL: How can I get the actual value of the Timer?

[Giannis Anastasopoulos]

Dear All,

I need a high frequency clock in order to measure the time between a couple of events.

In the RTC HAL there are functions that allow to retrieve the counter value and based on the used prescaler the time elapsed can be calculated.

But I need a clock frequency higher than the 32kHz and I am also out of RTC instances because I am using low power PWM, SoftDevice and a RTC  instance to keep track of time to my system.

So I thought of using the TIMER HAL available, but I do not see how I can get the value of the TIMER in timer mode.

What I need to do is to take the TIMER value whenever an interrupt is detected on a pin and then from those values calculate the frequency of the incoming signal.

Could you perhaps assist me with that?

[Vidar Berg]

Hello,

The capture function shown in the code snippet below can be used to read out the TIMER counter register using the driver APIs, or you can call  nrf_timer_cc_get() if you are working directly with the HAL.

const nrf_drv_timer_t timestamp_timer = NRF_DRV_TIMER_INSTANCE(1); // Selecting TIMER1. Make sure it's enabled in sdk_config.h    

/* Driver requires callback even if timer interrupts are not enabled */
void timer_event_handler(nrf_timer_event_t event_type, void* p_context)
{}

uint32_t timer_timestamp_get(void)
{
    return nrf_drv_timer_capture(&timestamp_timer, <CC register index>);
}
    
void timer_init(void)
{
    nrf_drv_timer_config_t timer_cfg = NRF_DRV_TIMER_DEFAULT_CONFIG;
    err_code = nrf_drv_timer_init(&timestamp_timer, &timer_cfg, timer_event_handler);
    APP_ERROR_CHECK(err_code);
} 

Note: for high accuracy measurements you may want to start the more accurate 64 MHz crystal oscillator (HFXO) clock. The system defaults to the HFINT clock.

Best regards,

Vidar