Setting TIMER2 interval

Question

How do I set TIMER2 to interrupt every 1 ms?

Sounds like a very basic question, but I haven't succeed. For TIMER1 I can get it working, but for TIMER2 the highest frequecy I have achieved is about 100 Hz.

The code is as follows:

void init_timer2(void)
{
	// Start 32 MHz crystal oscillator
	NRF_CLOCK->EVENTS_HFCLKSTARTED = 0;
	NRF_CLOCK->TASKS_HFCLKSTART = 1;
	// Wait for the external oscillator to start up
	while (NRF_CLOCK->EVENTS_HFCLKSTARTED == 0) {
		// Do nothing.
	}
	NRF_TIMER2->MODE = TIMER_MODE_MODE_Timer;
	NRF_TIMER2->PRESCALER = 4; // what should be here?
	NVIC_EnableIRQ(TIMER2_IRQn);
        NRF_TIMER2->BITMODE = TIMER_BITMODE_BITMODE_16Bit;
        NRF_TIMER2->CC[0] = ???;
        NRF_TIMER2->CC[1] = ???;
        NRF_TIMER2->CC[2] = ???;
        NRF_TIMER2->CC[3] = ???; 
	NRF_TIMER2->INTENSET = TIMER_INTENSET_COMPARE2_Enabled
	<< TIMER_INTENSET_COMPARE2_Pos;
	sd_softdevice_forward_to_application();
	NRF_TIMER2->TASKS_START = 1;
}

I don't know what should be put into the place of '???'s above. I guess there is a good documentation somewhere, so I would be happy to get a pointer there, too. Indeed, a working code would be best.

Edit: Format (please use preformatted text button when inserting code)

Håkon Alseth · Accepted Answer

Hi, 
 The prescaler sets the base timer tick like this (given in us):
TimerTick = 16M / 2^prescaler. 
 For instance, if we set 4:
TimerTick = 16M/2^4 = 1 us. 
 In order to generate an interrupt each 1ms: 
 
#define TIMER2_CC_DELAY 1000
...
NRF_TIMER2->PRESCALER = 4;
NRF_TIMER2->CC[0] = TIMER2_CC_DELAY; // Fbase = 16M/2^4 * 1000 = 1 ms.
/*Reset of init*/

 
 In your handler: 
 
void TIMER2_IRQHandler(void)
{ 
 if(NRF_TIMER2->EVENTS_COMPARE[0])
 {
 nrf_gpio_pin_toggle(18);
 NRF_TIMER2->EVENTS_COMPARE[0] = 0;
 // Need to update the CC[0]
 NRF_TIMER2->CC[0] += TIMER2_CC_DELAY;
 }
}
 
 For a more precise measurement you can add a static variable inside the interrupt handler to count instead of reading the CC[]-register. 
 Best regards
Håkon

Setting TIMER2 interval

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