PWM Measurement

erhanoztekin

Hello my friends,

I have a problem with the PWM measurement. I cannot on my parallax card.

scenario:

We have 3 different PWM inputs and we want to measure them separately. How can I write this code? We need to see how many milliseconds are 1 and how many milliseconds are 0.

JonnyMac

Here's a very simplistic approach:

pub measure_cycle(pin, p_high, p_low) | mask, t0, t1, t2

  mask := 1 << pin

  dira[pin] := 0 

  if (ina[pin] == 0)
    waitpeq(mask, mask, 0)
    t0 := cnt   
    waitpne(mask, mask, 0)
    t1 := cnt      
    waitpeq(mask, mask, 0)    
    t2 := cnt
    long[p_high] := (t1 - t0) / MS_001
    long[p_low]  := (t2 - t1) / MS_001

  else
    waitpne(mask, mask, 0)
    t0 := cnt   
    waitpeq(mask, mask, 0)
    t1 := cnt      
    waitpne(mask, mask, 0)    
    t2 := cnt
    long[p_low]  := (t1 - t0) / MS_001
    long[p_high] := (t2 - t1) / MS_001

You need to pass pointers to your high and low milliseconds variables, and define the MS_001 constant as the number of system ticks in one millisecond. Probably better, though, to use the system counters to measure the low and high periods. I wrote the attached object to measure the duty cycle output from a DMX lighting controller. This was used in a costume for a television show. The lighting operator changed the levels out of the DMX receiver which were translated by the Propeller into lighting and animation commands for the costume piece (Thunder's buckle from the TV show "Black Lightning"). I use the counters to measure the high and low periods of the cycle.