2 Replies Latest reply on Oct 23, 2014 5:58 AM by helic_263931

    Unexpected o/p resulted from timer ISR's



      My requirement is to output data in microseconds, and I am using many timer interrupts to achieve it in my code. The result is unexpected jitters in the o/p. It's definately not a good approach to have implementation inside ISR's, however i cannot think of anything else to achieve this timing. Any suggestions ??


      Note : The max tolerance allowed in the system is 2us. (Simple function execution take 1us)


      HW : PSOC5LP, Creator 3.0


      Screenshot : 5 timers are being used, Timer_Period_0 works fine, but Timer_Period_1 has varying intervals of 496, 504, 496, 504. I am not able to understand this behavior. Any help will be highly appreciated.

        • 1. Re: Unexpected o/p resulted from timer ISR's

          Can you post your project or at least describe functionality of


          timers and what ISR is doing  in a little more depth ?








          “File”                                                             Creator


          “Create Workspace Bundle”






          Regards, Dana.

          • 2. Re: Unexpected o/p resulted from timer ISR's

            Assuming a core clock of 80MHz, 1µs granularity / accuracy means just 80 clock cycles. Thats not much. Probably you want to use a hardware-based solution.


            The jitter you see might stem from the fact that the second timer ISR has a lower priority than the first, so it can only run when the first one isn't.


            Maybe you should explain a little bit more what you want to achieve.