PWM_32_v2 Frquency set math

bennettdan · 2011-03-10 20:19

Hello I have been looking at Beau's object and want to know how to figure the Period of the PWM.Duty comand to get adifferent frequency.
example:
PWM.Duty(7,50,5000)
I understand this is a PWM signal on Pin 7 at 50% duty cycle but I cant wrap my head around what frequncy the 5000 represents and how to figure it to a different frquency.
Thanks

kuroneko · 2011-03-10 20:30

PUB Duty(Pin,DutyCycle,Period)|BasePeriod,Ton,Toff     '' Pin = 0 to 31
    If Period <> 0
       If DutyCycle == 0                               '' DutyCycle = 0 to 100
          DutyMode(Pin,2)
          StateMode(Pin,1)
       If DutyCycle == 100
          DutyMode(Pin,1)
          StateMode(Pin,1)       
       If DutyCycle <> 0 and DutyCycle <> 100
          BasePeriod := (Period*1000)/Resolution       '' [COLOR="red"]Period is in micro seconds and[/COLOR]
          Ton := (DutyCycle * BasePeriod) / 100        '' [COLOR="red"]represents the repetition rate[/COLOR] 
          Toff := BasePeriod - Ton                     '' [COLOR="red"]of the PWM signal.[/COLOR] 
          if Ton == 0
             DutyMode(Pin,1)
          if Toff == 0
             DutyMode(Pin,2)
          if Ton ==0 and Toff == 0
             StateMode(Pin,0)
          if Ton<>0 or Toff<>0
             PWM(Pin,Ton ,Toff)                '' If Period = 0 then the pin is disabled
             DutyMode(Pin,0)       
    else
       StateMode(Pin,0)

bennettdan · 2011-03-11 00:17

I still dont see how to calculate this into a frequecy. sorry

kuroneko · 2011-03-11 00:45

From the included demo program:

PWM.Duty(1,50,[COLOR="red"]16665[/COLOR])        ''Create a [COLOR="red"]60Hz[/COLOR] 50% duty cycle on Pin1

A 60Hz signal has a 1/60Hz = 16.667ms period (16667us). Can you see the connection here? The 5000us from your example are equivalent to 200Hz.

bennettdan · 2011-03-11 14:09

I believe I have it now so if I want a 8khz PWM signal at 50% duty cycle on pin one then
PWM.Duty(1,50,125) = 1/8000hz = 0.000125ms (125us)
Is this correct?

kuroneko · 2011-03-11 17:15

bennettdan wrote: »

I believe I have it now so if I want a 8khz PWM signal at 50% duty cycle on pin one then
PWM.Duty(1,50,125) = 1/8000hz = 0.125ms (125us)

Yes, provided API and implementation match (good chance) that will give you an 8kHz signal.

PWM_32_v2 Frquency set math

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