Changing OS Tick from 1ms to 0.2ms

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  • Changing OS Tick from 1ms to 0.2ms

    Hi All,

    I would like to change the OS Tick (timer interrupt) from 1ms to 0.2ms without changing the behaviour of the OS_Delay() or any other time functions. I did the following until now:

    changing timer reload:
    #define TIMER_RELOAD (OS_PCLK_TIMER/5000 - 1)

    new tick handler:
    OS_HandleTick_Ex();

    What additional setting does i have to do now, to guarantee that a OS_Delay(10) call remains a delay of 10ms (I tried to modify with the OS_CONFIG macro, but this didn't work as expected)?

    I'm using embOS version 3.60a with IAR Embedded Workbench.

    Thanks for your help!

  • Hello,

    you cannot use OS_CONFIG() with a higher timer interrupt frequency, you can use it only with lower timer interrupt frequency.
    Why do you want to change the timer interrupt period to 0.2 msec?
    I suggest to use another hardware timer for the embOS system tick interrupt if you need this 0.2 msec period.

    Regards,
    Til
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  • Hi

    In my design i have a time-critical task which has to be activated once per millisecond. If I use an OS_Delay(1) in the task, the task is not called every millisecond, because there is the additional execution time of the code in the task.
    So i decided to use a hardware timer which sends an event every millisecond to the task and the task waits for this event. To avoid the task running in the timer's interrupt context, I used the OS_LeaveInterruptNoSwitch() at the end of the ISR. The problem now is, that the task becomes active after the next OS tick. A tick time of 1ms is in this case to slow, so i need a context switch every 0.2ms...

    I saw the following documentation for OS version 3.82: OS_TICK_Config(1, 10); // 10 kHz interrupts (0.1ms), 1ms tick
    Is it possible to modify the newer OS version 3.82 in a way that a context switch is done every 0.2ms but the OS tick for the delays remains at 1ms?

    Best Regards
    Stefan

  • swe wrote:

    I used the OS_LeaveInterruptNoSwitch() at the end of the ISR.
    From your description, it sounds like you should use OS_LeaveInterrupt() so that your task that's waiting on this event will be scheduled immediately (if there's no higher priority ready task).

    I believe that the use-case for OS_LeaveInterruptNoSwitch() is pretty rare.

    The post was edited 2 times, last by mwb1100 ().