Generating a pulse with RTC1 and PPI

RE: Generating a pulse with RTC1 and PPI

Susheel Nuguru — Thu, 30 Apr 2015 21:32:21 GMT

updated code for you, it wont compile as i dont remember API now, but you get the idea

RE: Generating a pulse with RTC1 and PPI

Susheel Nuguru — Thu, 30 Apr 2015 21:17:30 GMT

I am really sorry, I actually got confused looking at your use of GPIOTE, We do not have to use GPIOTE at all. Just toggle the pin in the interrupt handler. remove GPIOTE and PPI, then we just keep LFCLK

RE: Generating a pulse with RTC1 and PPI

Florin — Thu, 30 Apr 2015 18:53:59 GMT

I see. Is there actually any way to generate such pulse using less power than the method above?

RE: Generating a pulse with RTC1 and PPI

Susheel Nuguru — Thu, 30 Apr 2015 13:11:24 GMT

i think you can use timer as you are using gpiote anyways that uses HFCLK.

RE: Generating a pulse with RTC1 and PPI

Florin — Thu, 30 Apr 2015 13:07:27 GMT

Thanks Aryan for the quick answer, now it works.

So I guess that there's no way to avoid using RTC1_IRQHandler. A similar solution using TIMER1 doesn't require IRQ handling.

Cheers!

RE: Generating a pulse with RTC1 and PPI

Susheel Nuguru — Thu, 30 Apr 2015 11:36:49 GMT

void RTC1_IRQHandler(void)
{ 
  static volatile bool pin_state_high = true:

  if ( (NRF_RTC1->EVENTS_COMPARE[0] == 1) &&
      ((NRF_RTC1->INTENCLR & (1 << RTC_INTENCLR_COMPARE0_Pos)) != 0 ) )
	{
		NRF_RTC1->TASKS_CLEAR = 1;
		NRF_RTC1->EVENTS_COMPARE[0] = 0;

            if(pin_state_high)
            {
               NRF_GPIO->OUTCLR = (1 << PIN_NO);
            }
            else
            {
               NRF_GPIO->OUTSET = (1 << PIN_NO);
            }
            pin_state_high = !pin_state_high;
	}
}

/**
 * @brief Function for application main entry.
 */
int main(void)
{
	
	NRF_CLOCK->LFCLKSRC            = (CLOCK_LFCLKSRC_SRC_Xtal << CLOCK_LFCLKSRC_SRC_Pos);
    NRF_CLOCK->EVENTS_LFCLKSTARTED = 0;
    NRF_CLOCK->TASKS_LFCLKSTART    = 1;

    while (NRF_CLOCK->EVENTS_LFCLKSTARTED == 0)
    {
        // Do nothing.
    }
		
  NRF_RTC1->TASKS_STOP = 1;
  NRF_RTC1->TASKS_CLEAR = 1;               // clear the task first to be usable for later

  NRF_RTC1->PRESCALER = 32; //1kHz
  NRF_RTC1->CC[0] = 1000;  //1s interval
  NRF_RTC1->EVTENSET = RTC_EVTENSET_COMPARE0_Msk;
  NRF_RTC1->INTENSET = RTC_INTENSET_COMPARE0_Msk;
  NVIC_ClearPendingIRQ(RTC1_IRQn);
  NVIC_EnableIRQ(RTC1_IRQn);
  NRF_RTC1->TASKS_START = 1;

  nrf_gpio_set_dir_as_output_something (API not top of my head)

    while (true)
    {
        __SEV();
	    __WFE();

	    __WFE();            
        // Do Nothing - GPIO can be toggled without software intervention.
    }
}

RE: Generating a pulse with RTC1 and PPI

Susheel Nuguru — Thu, 30 Apr 2015 10:50:15 GMT

you are using GPIOTE module, this uses HFCLK