Sara aff/sff random freeze


I have an issue with my Sara AFF boards. They sporadically freeze execution.
The boards work as battery-powered trackers and they keep freeze randomly.

The boards wake up every minute by with RTC alarm and go back to sleep.

the library used is rtczero for the timer wakeup interrupt and also use rtc.standbyMode() for device sleep

void RTCZero::standbyMode()


I have not enabled WDT.

Are you aware of any issues related to the device not waking up from sleep sporadically?
I have seen this as a known issue for samd21. SAMD21 (SAMD21E16B) sporadically locks up and does not wake up from STANDBY sleep mode | AVR Freaks

Can I debug this by enabling try-catch blocks in order to deal with exceptions? If yes can you send a sample code the purpose of using exception handling for debugging is to determine is this is firmware related or not.

Thank you in advance,


Hi angeliki,

This is a well known issue to us.
You can solve it by adding this before sleep:

SysTick->CTRL &= ~SysTick_CTRL_TICKINT_Msk;

And this after sleep:

SysTick->CTRL |= SysTick_CTRL_TICKINT_Msk;



thanks for the response. I will try the fix.

It has been very time consuming to identify that is was an HW issue, is there a way to inform on such known issues through Sodaq support pages or forum?

Please update your documentation on the support page for low power sketches for samd21 boards to include this fix.


Hi angeliki,

I’d like to stress that this is an issue of atmel/microchip, if I recall correctly they note this in the errata.
I’ll make sure to flag our maintainer to update the code. Thought this was already done actually…


Hi @angeliki, @Thom,

The low power sketches on the support pages are updated with the code to solve the sleep issue.

Best regards,