freeRTOS tick (LFCLK?) goes nuts after bootloader DFU

RE: freeRTOS tick (LFCLK?) goes nuts after bootloader DFU

Joakim Jakobsen — Thu, 18 Jul 2019 12:06:06 GMT

Thanks for sharing the root cause and the fix with the rest of the community.

I'll forward your findings and feedback internally.

Best regards,
Joakim

RE: freeRTOS tick (LFCLK?) goes nuts after bootloader DFU

eyalasko — Thu, 18 Jul 2019 11:12:39 GMT

OK, I've nailed the problem -

On top the addition in my prev. post, there should be a short delay to compensate for the HFCLK-LFCLK jitter (see here).

For the sake of fellow developers attached is the final modified code (+ #include "nrf_delay.h" at the beginning of the file):

void vPortSetupTimerInterrupt( void )
{
    /* Request LF clock */
    nrf_drv_clock_lfclk_request(NULL);

    /* Configure SysTick to interrupt at the requested rate. */
	nrf_rtc_task_trigger (portNRF_RTC_REG, NRF_RTC_TASK_STOP);	// << Add these...
	nrf_delay_ms(1);	                                        // << ...two lines
    nrf_rtc_prescaler_set(portNRF_RTC_REG, portNRF_RTC_PRESCALER);
    nrf_rtc_int_enable   (portNRF_RTC_REG, RTC_INTENSET_TICK_Msk);
    nrf_rtc_task_trigger (portNRF_RTC_REG, NRF_RTC_TASK_CLEAR);
    nrf_rtc_task_trigger (portNRF_RTC_REG, NRF_RTC_TASK_START);
    nrf_rtc_event_enable(portNRF_RTC_REG, RTC_EVTEN_OVRFLW_Msk);

    NVIC_SetPriority(portNRF_RTC_IRQn, configKERNEL_INTERRUPT_PRIORITY);
    NVIC_EnableIRQ(portNRF_RTC_IRQn);
}

Nordic fellows,

Consider adding this fix (after validation of course) to the next SDK version/patch

Good luck

RE: freeRTOS tick (LFCLK?) goes nuts after bootloader DFU

eyalasko — Thu, 18 Jul 2019 09:29:19 GMT

Hi,

I've tracked down the root cause - It is indeed a problem with the rtos tick clock source (RTC1).

I've added RTC1->PRESCALER value printout in one of the tasks startup code.

On normal system start, this value ix 0x1F as expected (dividing 32768Hz LFCLK by 32 = 1024Hz)

On system start after BL DFU, this value is 0 !! hence the x32 tick speed.

The nRF52832 datasheet mentions that the prescaler has to be stopped before its value can be set, so I've added a call to stop the clock in the rtos tick initialization routine vPortSetupTimerInterrupt(), however it still does not solve the problem.

void vPortSetupTimerInterrupt( void )
{
    /* Request LF clock */
    nrf_drv_clock_lfclk_request(NULL);

    /* Configure SysTick to interrupt at the requested rate. */
	nrf_rtc_task_trigger (portNRF_RTC_REG, NRF_RTC_TASK_STOP);	// << Added this line
    nrf_rtc_prescaler_set(portNRF_RTC_REG, portNRF_RTC_PRESCALER);
    nrf_rtc_int_enable   (portNRF_RTC_REG, RTC_INTENSET_TICK_Msk);
    nrf_rtc_task_trigger (portNRF_RTC_REG, NRF_RTC_TASK_CLEAR);
    nrf_rtc_task_trigger (portNRF_RTC_REG, NRF_RTC_TASK_START);
    nrf_rtc_event_enable(portNRF_RTC_REG, RTC_EVTEN_OVRFLW_Msk);

    NVIC_SetPriority(portNRF_RTC_IRQn, configKERNEL_INTERRUPT_PRIORITY);
    NVIC_EnableIRQ(portNRF_RTC_IRQn);
}

On what circumstances does this register (RTC1->PRESCALER) is zerod (other than hard reset)

What can be the reason it is not being set as requested in vPortSetupTimerInterrupt() ?

Thanks

RE: freeRTOS tick (LFCLK?) goes nuts after bootloader DFU

Joakim Jakobsen — Tue, 16 Jul 2019 06:49:59 GMT

Hi.

We are actually a little short on FreeRTOS and DFU expertise at the moment, due to summer vacation here in Norway. I'll try to track down the root cause of this, but some delay in response time will be expected.

Sorry for the inconvenience.
Best regards,
Joakim Jakobsen