10 years, 8 months ago.  This question has been closed. Reason: Unclear question

Problem with timer in a class

Hi !

I'm having a problem with a class that I'm creating to read a PWM on a digital input.

This class takes an InterrputIn and a timer as parameter and then get the duty_cycle and the period of the signal on the interrupt in.

My problem is : when I read the period, the value of the timer isn't always the same. I used the same code out of the class and it works, that's why I think that the class is the problem. To solve it I now use pointers for the InterruptIn and the timer but it doesn't work.

However, my code works for the duty_cycle which is good, but strange.

The code :

class CPwmIn
{
protected:
  Timer* t;
  float duty_cycle;
  float period;
public:
    CPwmIn(InterruptIn* _PwmIn,Timer* _t):t(_t),duty_cycle(0),period(0)
    {
      _PwmIn->rise(this, &CPwmIn::start_timer);
      _PwmIn->fall(this, &CPwmIn::stop_timer);
    }
    
    void start_timer()
    {
      period=t->read_us();
      period = period/1000000;
      printf("%f \n\r\t",period);
      t->reset();
      t->start();
    }

    void stop_timer(){
        duty_cycle = t->read_us();
        duty_cycle = duty_cycle/1000000;
        duty_cycle = duty_cycle / period;
        }
    float GetPeriod(){return period;}
    float GetDutyCycle(){return duty_cycle;}
};


Timer t;
AnalogIn pot(p20);
PwmOut test(p22);
InterruptIn _m2(p15);
CPwmIn e1(&_m2,&t);

void test1(){
    test.period(0.0025);
    while(1){
            test.write(pot.read());
        }
    }

Output :

/media/uploads/adrienPPS/screen_shot_2015-03-14_at_22.13.34.png

Thank you !

ANSWER : No printf in an ISR...