allow rtos idle thread to call sleep();

[maclobdell]

To enable power efficiency, the rtos thread should call sleep(). To my knowledge, this can be done regardless if the debugger interface is connected (at least it can on the Kinetis MCUs). If the debugger interface is connected, the device may not achieve as great of power savings, but it still can enter low power mode. Something is better than nothing.

[0xc0170]

@maclobdell Did you test this on the lpc boards that have local filesystem? There's relevant issue here: #143

cc @Sissors @neilt6 @bogdanm

[bogdanm]

Cc @bulislaw (he's working on something related to this).

[bulislaw]

I'm working on a tickless mode, where we'll stop the SysTick, set wakeup timer and then call sleep.

[0xc0170]

I cant make lpc11u24 neither lpc1768 debugging work (uvision, iar, makefile). Anyone to test for those platforms this patch?

[bogdanm]

I'm working on a tickless mode, where we'll stop the SysTick, set wakeup timer and then call sleep.

I believe this will eventually be a better solution, since tickless mode allows the OS to keep track of the time even while the MCU is asleep.

[sg-]

Closing in favor of #2547

@maclobdell please make sure sleep() gets enabled by default for the non-tickless mode.

[maclobdell]

re-opening because #2547 is postponed.

[sg-]

@maclobdell can you resolve the conflict?

[sg-]

@maclobdell github is still not happy :)

[maclobdell]

created new pull request #3019 to replace this one. The change is identical. Trying to avoid potential git issue with this PR.