Problem running a 10kHz PWM on a Timer

RE: Problem running a 10kHz PWM on a Timer

Phil — Tue, 04 Nov 2014 16:45:04 GMT

Hello Stefan,

Thanks for the link. One more thing though, I did manage to get the PWM on compare 0 to work fine, however I tried in parallel to run an interrupt on Compare 1 every 10msec and that does not work. The interrupt is not entered and my PWM is 20msec. What am I getting wrong?

// Init TIMER2 for 10kHz PWM
NRF_TIMER2->MODE = TIMER_MODE_MODE_Timer;           // Set the timer in Counter Mode
NRF_TIMER2->TASKS_CLEAR = 1;                        // Clear the tasks first to be usable for later
NRF_TIMER2->PRESCALER = 4;                          // 2^PRESCALER (values authorized 1 to 9) 4 : 16MHz / 16 = 10MHz
NRF_TIMER2->BITMODE = TIMER_BITMODE_BITMODE_16Bit;  //Set counter to 16 bit resolution

// Init OC0 PWM
NRF_TIMER2->CC[0] = 50;
PWM_TIMER->SHORTS = (TIMER_SHORTS_COMPARE0_CLEAR_Enabled << TIMER_SHORTS_COMPARE0_CLEAR_Pos);

// Enable OC1 interrupt on TIMER2
NRF_TIMER2->CC[1] = 10000;
PWM_TIMER->SHORTS = (TIMER_SHORTS_COMPARE1_CLEAR_Enabled << TIMER_SHORTS_COMPARE1_CLEAR_Pos);
NVIC_EnableIRQ(TIMER2_IRQn);

// Start TIMER2
NRF_TIMER2->TASKS_START = true;

Interrupt :

void TIMER2_IRQHandler(void)
{

    if (NRF_TIMER2->EVENTS_COMPARE[1] != 0)
    {
        NRF_TIMER2->EVENTS_COMPARE[1] = 0; // Reset event

       // Code to execute

    }
}

Regards Phil

RE: Problem running a 10kHz PWM on a Timer

Stefan Birnir Sverrisson — Tue, 04 Nov 2014 14:00:57 GMT

Hi Phil. If you feel that you have received a good answer to you question, please accept that answer. Also remember to vote for good answers. Thanks

RE: Problem running a 10kHz PWM on a Timer

Stefan Birnir Sverrisson — Tue, 04 Nov 2014 13:59:30 GMT

For further PWM code reference, there is a PWM library available here for nRF51.

RE: Problem running a 10kHz PWM on a Timer

Stefan Birnir Sverrisson — Tue, 04 Nov 2014 13:56:39 GMT

Thank you for your valuable input Tony.

RE: Problem running a 10kHz PWM on a Timer

Phil — Mon, 03 Nov 2014 16:48:36 GMT

Hi Tony,

Great thanks. Just the thing I needed to know. Works great now!

Thanks for the help

Phil

RE: Problem running a 10kHz PWM on a Timer

Tony.X — Mon, 03 Nov 2014 16:31:23 GMT

Hi Phil,

You can totally get rid of the interrupt handler if you don't want to change the desired frequency on the fly.

This can be done by setting the SHORT register.

Add one more line in Timer init function,

PWM_TIMER->SHORTS = (TIMER_SHORTS_COMPARE0_CLEAR_Enabled << TIMER_SHORTS_COMPARE0_CLEAR_Pos);

This enables the timer to clear the internal counter to 0 when it reaches CC[0].

Hope this will help.

Tony