[riot-devel] xtimer and lower core/bus frequency in low power mode

Anon Anonymous anon1644072 at gmail.com
Tue Sep 13 02:22:17 CEST 2016

Good day everyone,

I implemented low power mode for STM32L151-based board and looking for a
solution of following problem.

When xtimer_sleep(10) executed, the MCU meant to go into low power mode for
1 second.
Assume that current clock frequency is 32 MHz, after I lower frequency to
4MHz MSI and entered to sleep, the timer will runt 8 times slower and
xtimer_sleep(1) becomes xtimer_sleep(8) due to lower bus (and thus, timer)
clock frequency.

How I should make xtimer aware about lower clock frequency? I tried to
directly modify xtimer's TIM5 prescaler with no luck.

Best regards,
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