nrf51822 Timer calculation

RE: nrf51822 Timer calculation

Jørgen Holmefjord — Mon, 10 Dec 2018 09:07:22 GMT

Please post your request in a new question, to avoid filling this question with too much information.

RE: nrf51822 Timer calculation

ps_anu — Mon, 10 Dec 2018 07:07:53 GMT

hi...jorgen ... how does timer works ....... if i want to execute the data for 1 minute ..where i have declare the time ?

RE: nrf51822 Timer calculation

Dhiraj — Mon, 04 Dec 2017 11:03:54 GMT

Hello Jorgen, I haven't tried RTC yet. But I used another method in which I made timer of 1 milli second using TIMER1. And when interrupt is fired i.e., 1 milli sec are over, a "counter" variable is incremented. As the counter reaches 8000, 8 seconds are over.

RE: nrf51822 Timer calculation

Jørgen Holmefjord — Mon, 04 Dec 2017 08:48:25 GMT

You are correct, I only considered the calculation, not which timer instance you were using. Have you considered using RTC for generating the periodic timer? RTC have 24-bit registers and runs at 32.768 kHz, which is more suited for such long periods like 8s.

RE: nrf51822 Timer calculation

Dhiraj — Thu, 30 Nov 2017 08:33:23 GMT

Hello Jørgen,

The timer 1 cannot operate in 32bit mode. So I think such higher count of CC have no effect on the timer.

RE: nrf51822 Timer calculation

Dhiraj — Wed, 29 Nov 2017 07:26:59 GMT

Here I am trying to toggle the led state for every 8 sec. I see that even if I change the value of NRF_TIMER2->CC[0] to 1000000, there is no change. When I keep the prescalar at 4 it toggles fast. At prescalar 8, it toggles at ~2-3 seconds. Am I missing something?

There was mistake in code which I mentioned previously

void start_timer(void)
{    
  NRF_TIMER2->MODE = TIMER_MODE_MODE_Timer;  // Set the timer in Counter Mode
  NRF_TIMER2->TASKS_CLEAR = 1;               // clear the task first to be usable for later
  NRF_TIMER2->PRESCALER = 8;                             //Set prescaler. Higher number gives slower timer. Prescaler = 0 gives 16MHz timer
  NRF_TIMER2->BITMODE = TIMER_BITMODE_BITMODE_32Bit;     //Set counter to 16 bit resolution
  NRF_TIMER2->CC[0] = 500000;                             //Set value for TIMER2 compare register 0
    
  // Enable interrupt on Timer 2, both for CC[0] and CC[1] compare match events
  NRF_TIMER2->INTENSET = (TIMER_INTENSET_COMPARE0_Enabled << TIMER_INTENSET_COMPARE0_Pos) | (TIMER_INTENSET_COMPARE1_Enabled << TIMER_INTENSET_COMPARE1_Pos);
  NVIC_EnableIRQ(TIMER2_IRQn);
    
  NRF_TIMER2->TASKS_START = 1;               // Start TIMER2
}
    
/** TIMTER2 peripheral interrupt handler. This interrupt handler is called whenever there it a TIMER2 interrupt
 */
void TIMER2_IRQHandler(void)
{
  if ((NRF_TIMER2->EVENTS_COMPARE[0] != 0) && ((NRF_TIMER2->INTENSET & TIMER_INTENSET_COMPARE0_Msk) != 0))
  {
    // toggle the led
    NRF_TIMER2->EVENTS_COMPARE[0] = 0;           //Clear compare register 0 event 
  }

}

RE: nrf51822 Timer calculation

Jørgen Holmefjord — Tue, 28 Nov 2017 13:32:31 GMT

Did you try it out? Prescalar of 8 should give a CC value of 500 000 for 8 seconds timer ( (16 MHz / (2^PRESCALAR)) * 8 s = 500 000).