STM32F2xx ctl tick time

Follow

Gordon Scott

• February 29, 2012 10:32

Hi Guys,

I appear at present to be getting a wrong timeout to a tick and I can't yet find why.

Within a task, I have some code like the following:

    n = ctl_get_ticks_per_second();
    while (1)
    {      
         ctl_timeout_wait(ctl_get_current_time());    // every 1ms

         tick_ms++;
         if( tick_ms & 1 )
         {
              set_BNC_out_high();
         } else {
             set_BNC_out_low();
         }
    }

Which normally would toggle the state of the output every millisecond, but in this case it's every 10ms.

'n' is 1000, which suggests ctl thinks it's doing 1ms ticks. But the 'scope tells a different story.

AFICS the only change I have from the default setup is that I have 12MHz crystal, not 25MHz, so I have changed PLL_M to from 25 to 12.

Does anyone have any hints of how I can find why I get the unexpected time. I can't presently find it, RCC registers seem sensible from the setup.

0

• 

  Michael Johnson

  • February 29, 2012 12:08

  I don't follow your code (I guess it hasn't seen a compiler).

  The CTL timer interrupt fires every 10ms and the counter is incremented by 10. So it's a ms counter that is increment every 10 ms.

  0

  Comment actions Permalink
• 

  Gordon Scott

  • February 29, 2012 13:52

  Hi Michael,

  It's a cut-down from the whole code showing just the essential bits.

  It would not compile without the omitted stuff.

  The call to the ctl wait was cut and pasted from STM32F1xx code. Your answer suggets either things have changed, or in my earlier code I'd done something, about which obviously I've forgotten, to shorten it to 1ms.

  Is there a means to get my ticker task running at 1ms increments instead of 10ms incremenms?

  Thanks.

  0

  Comment actions Permalink
• 

  Michael Johnson

  • February 29, 2012 14:00

  You'll need to modify the ctl_start_timer function it's in the project - right click on the stm32_ctl.c file and select import to take a project local copy.

  Regards

  Michael

  0

  Comment actions Permalink
• 

  Gordon Scott

  • March 01, 2012 10:12

  Thanks Michael, that's done it.

  For the record, if anyone else looks for the answer, this was the change I made:

  void ctl_start_timer(CTL_ISR_FN_t timerFn)
  {    
    userTimerISR = timerFn;  
    SysTick->CTRL = SysTick_CTRL_TICKINT_Msk | SysTick_CTRL_ENABLE_Msk;
    // We want 1ms ticks, not 10ms.        ** GLS **
    //SysTick->LOAD = (SystemCoreClock/8/100)-1; // interrupt every 10 ms
    SysTick->LOAD = (SystemCoreClock/8/1000)-1; // interrupt every 1 ms
  #ifdef CTL_TASKING
    // So we don't need to increment by tens    ** GLS **
    // ctl_time_increment = 10; // so increment the counter by 10 to get the ms counter
    ctl_time_increment = 1;    // I think this is actually redundant.    ** GLS **
  #endif
   .....

  0

  Comment actions Permalink

Please sign in to leave a comment.