Thanks Juan,
That's a lot of information to digest. It will take me a bit of time
to go through.
-- Kees
On 27-05-19 14:17, Juan Ignacio Carrano wrote:
Hi Kees,
Some observations:
1- WFI will not send you to the deepest sleep states- clocks are
gated, but many things remain powered.
2- If you are using the timer module and depending on you clock
configuration you may experience more or less frequent wake ups.
Whether this is acceptable is up to you.
3- Normally, if no thread is runnable (i.e. all are waiting/blocked) the
idle thread is run and that has a loop which sends the MCU to the
deepest state possible (considering the currently-enabled
peripherals). This means that in many cases the explicit WFI is not
needed if in your
"while(forever)" loop you put some call that blocks waiting for the
events you are interested in.
The interaction between (1) and (3) means that by doing a WFI in a
thread it is possible that you don't sleep as deep as you could:
- The current thread will be blocked on the WFI instruction until an
event arrives.
- In the meantime, control will not go back to the kernel.
- This means the idle thread will not run (from the schedulers point of
view, you thread is still running).
- The pm_whatever() call in the idle thread will not run.
In conclusion, try to use the default mechanism if you can.
Regards,
Juan.
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