[riot-devel] Implementation of a real low power timer for sleep/stop mode (idle thread)

Joakim Nohlgård joakim.nohlgard at eistec.se
Mon Feb 15 13:52:06 CET 2016

Hi Bernhard,
​It should be possible with some modifications to use a slow clock as the
xtimer source. There are a few developers working on improving the low
power operation in RIOT. As you discovered, the periph/timer API currently
needs to be updated to support non-MHz timer frequencies. I have a PR open
which will be merged some time soon, hopefully. Some PRs of interest:

https://github.com/RIOT-OS/RIOT/pull/4040 - support for non-1MHz operation
of periph/timer
https://github.com/RIOT-OS/RIOT/pull/3990 - xtimer 32768 Hz support, needs
some love, there are problems with it right now.
https://github.com/RIOT-OS/RIOT/pull/4065 - kinetis: periph/timer use LPTMR
for TIMER_0, PIT for TIMER_1, TIMER_2
https://github.com/RIOT-OS/RIOT/pull/2605 - kinetis: Add LPM implementation
- mostly an experiment remaining as a memo, needs to be reworked.

Once #4040 gets merged I hope to be able to resume working on xtimer 32768
Hz support. There are some other stuff that I need for work which are more
urgent though.

Best regards,

On Mon, Feb 15, 2016 at 12:36 PM, Bernhard Nägele <
bernhard at naegele-privat.de> wrote:

> Hello everyone,
> the STM32L053 has a low power timer which could be configured to be
> clocked by an internal 37kHz oscillator.
> For real low power applications it would be a good idea to use this timer
> during sleep/stop mode (for the idle tread).
> As far as I know the context switching is performed by the xtimer which
> needs a 1MHz clock in its configuration.
> Would it be possible to use such a slow clock for this purpose?
> Best regards,
> Bernhard
> _______________________________________________
> devel mailing list
> devel at riot-os.org
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