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Resetting a Timer

Question asked by burkhart.thomas on Jul 22, 2011
Latest reply on Jul 25, 2011 by burkhart.thomas
Hi,

I have the following problem.

I have a RFID-Reader Chips from Melexis (90109) connected to two GPIO Pins (Clock and Data).

I process the incoming data with an EXTI handler that is triggert on the falling edge of the clock pin.

This works fine.

To detect if a transponder has left the field I must detect if the clock line is no longer atcive for a certain amount of time.

My current approach is that I set up TIM2 as normal Timebase counter with an TIM_UPDATE IRQ-Handler as sort of watch dog for the clock line.

In the EXTI handler I tried to reset TIM2 with

  TIM_SetCounter(TIM2, 0);

so that as long as I receive clock pulses shorter than the timer period, the TIM2 Handler should not be called at all.

If the clock stops, TIM2 handler should set a flag to signals the main loop that the transponder was removed.

So far the idea, but reality shows that although I reset the TIM2 counter regulary I always get the TIM2 IRQ in it's normal period.

Do I have to reset/restart a timer in a different way?

Best
Tom 

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