RE: Timer in counter mode

Edvin — Thu, 26 Apr 2018 14:53:39 GMT

You should look into the PPI.

Here is an example, which uses the PPI. It uses a timer to toggle a GPIO, but you can change the GPIO to "event" instead of "task", and use the timer in counter mode. The timer can be configured something like this:

void timer_init()
{
NRF_TIMER3->BITMODE = TIMER_BITMODE_BITMODE_24Bit << TIMER_BITMODE_BITMODE_Pos;
NRF_TIMER3->PRESCALER = 0;
NRF_TIMER3->SHORTS = TIMER_SHORTS_COMPARE0_CLEAR_Msk << TIMER_RELOAD_CC_NUM;
NRF_TIMER3->MODE = TIMER_MODE_MODE_Counter << TIMER_MODE_MODE_Pos;
NRF_TIMER3->CC[TIMER_RELOAD_CC_NUM] = TIMER_RELOAD;
}

Then you need to start the timer with:

NRF3_TIMER3->TASKS_START = 1;

Then configure the GPIO like in the example, and set a PPI channel something like the following:

NRF_PPI->CH[PPI_CH_1].EEP = (uint32_t)&NRF_GPIOTE->EVENTS_IN[GPIOTE_CH];

NRF_PPI->CH[PPI_CH_1].TEP = (uint32_t)&NRF_TIMER3->TASKS_COUNT;

Then you can get the count value by checking the timer value:

NRF_TIMER3->TASKS_CAPTURE[0];

and check the value with:

uint32_t value = NRF_TIMER3->CC[0];

you can also reset the counter using:

NRF_TIMER3->TASKS_CLEAR;

I have not tested this right now, so the calls are from my memory, but it should look something like this.

Best regards,

Edvin