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1. 

   samtal
   Member

   I have a 'for' loop in which I wish to do something (for test, make a time reading) each predefined time interval of several tens micros.
   I initialize a hardware compare timer, define interrupt handler, sets the period and starts the timer in the setup.
   I expect the loop to halt in each cycle until the timer reaches a certain value (0 or any) and then make the next loop.
   At the end of the loop number, the program is expected to exit the loop and proceed in the main loop, until the function will be called again.
   Here is a basic example of what I need:

   void program()
   {
   for (int i = 0; i<100;i++)
   {
   while (timer !=0) //Wait until timer fires (resets to 0 or other).

   timearray[i]=micros();
   }
   }
   I assume I need to use an interrupt(?), but I can not use an external function, as I want the interrupt inside my function.
   Does anyone know how I can make this work?
   Thanks
   samtal

   Posted 4 years ago #
2. 

   gbulmer
   Moderator

   samtal - According to the RM0008 manual, in section 15.3.2 "Counter modes", there are several ways to do this without any interrupt.
   The simplest solution looks like setting the counter for the whole timer block (using pre-scalar and auto-reload value) so that you can see the event in the timers registers

   You could just poll the appropriate bit directly (I think it is the UIF bit 15.4.5 "TIMx status register (TIMx_SR)", but I haven't read that carefully enough to be sure. Pulling directly using something like like a register address.)

   The alternative is to write a tiny interrupt handler which sets a 'flag'.
   The documentation is at http://leaflabs.com/docs/lang/api/hardwaretimer.html#using-timer-interrupts

   HardwareTimer timer(2);
   volatile int flag = 0;
   
   void setup() {
       // set up timer
       // attach interrupt
       timer.attachCompare1Interrupt(timer2interrupt);
   }
   
   void loop() {
       //...
       flag = 1;
       while (flag) ;  // wait for the flag to clear, and hence synchronise
       flag = 1
       for (int i = 0; i<100;i++) {
           while (flag !=0) //Wait until timer fires (resets to 0 or other).
   
           timearray[i]=micros();
           flag = 1;
       }
   }
   
   void timer2interrupt() {
        flag = 0;
   }

   Posted 4 years ago #

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