app_scheduler and TIMER1 hardfault

[Xian]

I have the code below initializing TIMER1 and and IRQ every 1ms. I call app_sched_event_put within the timer and I get a Hardfault.

Any hints on what is going on ?

Thanks.

void high_res_timer_init(){
    // Stop timers
    NRF_TIMER1->TASKS_STOP  = 1;
    // Clear timers
    NRF_TIMER1->TASKS_CLEAR = 1;
    // Set the timer1 in Timer Mode, and timer 2 in counter mode
    NRF_TIMER1->MODE        = TIMER_MODE_MODE_Timer;
    // Prescaler 4 produces 1MHz for timer1 frequency
    NRF_TIMER1->PRESCALER      = 4;
    // Ensure 16 bit mode on both timers
    NRF_TIMER1->BITMODE        = TIMER_BITMODE_BITMODE_16Bit;
    // 1ms interrupt
    NRF_TIMER1->CC[0] = 1000;
		NRF_TIMER1->INTENSET = (TIMER_INTENSET_COMPARE0_Enabled << TIMER_INTENSET_COMPARE0_Pos);
		NVIC_EnableIRQ(TIMER1_IRQn);
	
    // Start timers
    NRF_TIMER1->TASKS_START = 1;
}

void TIMER1_IRQHandler(void) {
	
	
	if ((NRF_TIMER1->EVENTS_COMPARE[0] != 0) && ((NRF_TIMER1->INTENSET & TIMER_INTENSET_COMPARE0_Msk) !=0)) {
		NRF_TIMER1->EVENTS_COMPARE[0] = 0;
		NRF_TIMER1->TASKS_CLEAR = 1;
		nt_time++;
		if (count++ > 20) {
			app_sched_event_put(&nt_time, sizeof(nt_time), mag_scheduler_event_handler);
			count = 0;
		}
		dpin_toggle();
	}
}

[Eric Stutzenberger]

Can you provide more details about what line of code causes the hard fault? I haven't used the app scheduler much. Is it somewhere within app_sched_event_put()?

[Eric Stutzenberger]

I'm not sure of the default interrupt priority off the top of my head, but when setting up the interrupt, the priority should be set to either app high or app low. Not sure how critical this particular functionality is but I'd suggest setting the priority to see if it helps in anyway: NVIC_SetPriority(TIMER1_IRQn, APP_IRQ_PRIORITY_LOW); //APP_IRQ_PRIORITY_LOW defined in app_util_platform.h

[Susheel Nuguru]

EricS is right, ill explain little more of what he said. It must be happening when calling CRITICAL_REGION_ENTER(); inside app_sched_event_put. This happens when your timer interrupt handler priority is higher than SVC priority (2) and you have definedSOFTDEVICE_PRESENT in your project.

Setting below when initializing the timer interrupt should do the trick.

NVIC_SetPriority(TIMER1_IRQn, APP_IRQ_PRIORITY_LOW);

[Xian]

Thank you, this is the root of the issue. I am facing now an issue as I also have a GPIOTE interrupt event with the same APP_PRIORITY_LOW and they are fighting one against each other. I tried to set one of them to a lower priority (4) but then it would just hardfault again

[Susheel Nuguru]

nRF51 has Cortex M0 processor which allows only four programmable priority levels (0-3). Setting any thing else than that will obviously hardfault immediately on the chip level. Please use only APP_PRIORITY_HIGH or APP_PRIORITY_LOW macro for application specific priority levels. If you use APP_PRIORITY_HIGH, then it will be higher priority than SVC calls and hence your application wont be able to make any softdevice calls in this interrupt priority context.