Setting TIMER2 interval

RE: Setting TIMER2 interval

Craig — Mon, 03 Apr 2017 17:43:23 GMT

Hello, I am struggling with timers in general, I so happen to use TIMER2 as well with my BLE UART app all I need is a way to generate 1sec and in another similar app 2 ms, 2 versions of HEX, how can I generate this? I seem to be calculating it wrong according to my scope output, this example was not anywhere near 1 ms and neither is the math in the comments.

RE: Setting TIMER2 interval

Håkon Alseth — Tue, 13 May 2014 10:48:34 GMT

The reason this must be there is because the timer is not cleared between each interrupt. When you've finished your first interrupt, the timer will keep on incrementing until it overflows. You then have two options:

Keep updating the CC-register
Clear the timer between each interrupt. This can be done manually, or via SHORTS register.

Best regards Håkon

RE: Setting TIMER2 interval

Mo A — Mon, 12 May 2014 12:15:24 GMT

Hello Håkon, Thanks for this. I was able to start working with the timer by referring this code. But I have a question that whether the line, NRF_TIMER2->CC[0] += TIMER2_CC_DELAY; can be removed here ? But when I tried that , the toggling was not proper. why is this so?

thanks, Mo

RE: Setting TIMER2 interval

Håkon Alseth — Fri, 28 Mar 2014 09:42:58 GMT

Hi Jarmo,

It's most likely because you enabled CC[2]: NRF_TIMER2->INTENSET = TIMER_INTENSET_COMPARE2_Enabled Enabling CC[0] is done like this: NRF_TIMER2->INTENSET = TIMER_INTENSET_COMPARE0_Enabled

BR Håkon

RE: Setting TIMER2 interval

Jarmo — Fri, 28 Mar 2014 09:36:52 GMT

For some reason, I had to use CC[2] instead of CC[0] to get it working. Could it has something to do with S110 soft device which I am using at the same time? Anyway, thanks!

RE: Setting TIMER2 interval

Håkon Alseth — Thu, 27 Mar 2014 16:12:36 GMT

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