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RTX - Tick supression possible?

Hi,

I am evaluating various RTOS solutions for a very low power Cortex-M3 based device, and one of my requirements is that the MCU isn't woken up every n ms to handle a clock tick.

Various RTOS support the idea of 'tick supression' (called various things - tickless operation, managed sleep etc) - with the basic idea being that the next scheduled event is detected and the core put to sleep until that time, at which point the clocks etc are updated.

I don't see that RTX supports this feature, can anyone confirm either way?

Many thanks
Jon

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  • Note that many ARM chips can have timers spanning very long times. So instead of having a timer generating an interrupt every 1ms, you can reconfigure the same timer to instead generate the next interrupt in 34397ms if you know that this is the shortest time for any sleeping thread. So the processor can then sleep for 34.397 seconds, or until a peripherial interrupt (such as UART receive) happens. After that, the timer can be reconfigured to again tick at 1ms while the threads do what they need to do until you once more have zero threads that has tasks to do.

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  • Note that many ARM chips can have timers spanning very long times. So instead of having a timer generating an interrupt every 1ms, you can reconfigure the same timer to instead generate the next interrupt in 34397ms if you know that this is the shortest time for any sleeping thread. So the processor can then sleep for 34.397 seconds, or until a peripherial interrupt (such as UART receive) happens. After that, the timer can be reconfigured to again tick at 1ms while the threads do what they need to do until you once more have zero threads that has tasks to do.

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