Capture timer value

RE: Capture timer value

pascal defesche — Tue, 13 May 2014 11:22:28 GMT

Ok thanks again for your help!

RE: Capture timer value

Håkon Alseth — Tue, 13 May 2014 10:46:15 GMT

Hi Pascal,

I just checked with one of our developers regarding this. Once the task has been set internally (ie: the TASKS_CAPTURE register has been set) it will be executed in one clock cycle.

Best regards Håkon

RE: Capture timer value

pascal defesche — Mon, 12 May 2014 08:13:55 GMT

The nRF51 reference manual chapter 17.1.4 specifies the clear, count and stop task will guarantee to take place within one clock cycle of HFCLK.

When using capture task how long will it take for the timer value to be available in the register? Within one clock cycle?

RE: Capture timer value

pascal defesche — Mon, 28 Apr 2014 15:33:33 GMT

i have found the problem: the bluetooth stack has higher priority causing tasks_clear to be processed later

RE: Capture timer value

pascal defesche — Mon, 28 Apr 2014 11:23:08 GMT

Is it possible to clear the timer at a compare event? I need the timer to reach a maximum value of 31250 and immediately clear the timer. I've tried using the following code but it results in a value sometimes over the 31250 because the mcu needs to set clear task.

void TIMER1_IRQHandler(void)
{
//0,125s compare event
if(NRF_TIMER1->EVENTS_COMPARE[0]) //compare event happened
{
	NRF_TIMER1->EVENTS_COMPARE[0] = 0;//set compare register again to 0
	NRF_TIMER1->TASKS_CLEAR = 1;//set count value to 0
	half_sec++;					//value indicating half seconds
	NRF_TIMER1->CC[0] = 31250; //Need to update the CC[0] with new compare value
	nrf_gpio_pin_toggle(18); //indication for compare event
}
}

Is it possible implementing this without the timer getting a value above 31250?

RE: Capture timer value

pascal defesche — Mon, 14 Apr 2014 09:03:46 GMT

ah yes ofcourse, thanks!

RE: Capture timer value

Nikita — Fri, 11 Apr 2014 19:47:15 GMT

You are already using CC[0] register for COMPARE0 event interrupt, so if you want to read current timer counter value you need to trigger CAPTURE task for another channel i.e.: NRF_TIMER2->TASKS_CAPTURE[1] = 1; u_sec = (NRF_TIMER2->CC[1]);

RE: Capture timer value

pascal defesche — Fri, 11 Apr 2014 14:16:36 GMT

I have one more question regarding the timers:

In my case im initialising the timer to tick with 8 u sec and im generating an compare event each 20ms (so 2500 ticks). This works and is located in my IRQ handler, but now in the main (for loop) i want to read the current value in the count register is this just simply possible with the following code?

for (;;)
    {
    	//NRF_TIMER2->TASKS_CAPTURE[0] = 1;
    	u_sec = (NRF_TIMER2->CC[0]); //value in us with 8us resolution
    	if (m_do_update)
    	        {
    				nrf_gpio_pin_set(LED_6);
    	            advertising_init();
    	            m_do_update = false;
    	            nrf_gpio_pin_clear(LED_6);
    	        }

    }

Writing tasks_capture[0]=1 will stop the timer event, thats why i commented it.

Regards, Pascal

RE: Capture timer value

Håkon Alseth — Thu, 10 Apr 2014 07:40:08 GMT

It's true that the register is 4 bit, however the valid range for PRESCALER is from 0 to 9.

BR Håkon

RE: Capture timer value

pascal defesche — Wed, 09 Apr 2014 15:04:24 GMT

Thanks, after setting NRF_TIMER2->TASKS_CAPTURE[0] = 1; i can read its value. Why prescaler 14 is not valid? Thought max = 2^4(16)??

Cheers

RE: Capture timer value

Håkon Alseth — Wed, 09 Apr 2014 14:47:54 GMT

Hi,

Setting NRF_TIMERx->PRESCALER = 14 is not valid. It's only valid from 0 to 9. Note that you should write NRF_TIMER2->TASKS_CAPTURE[0] = 1; to start the task.

BR Håkon