> Great, very simple, very good.
>
> Bill
>
> ----- Original Message -----
> From: "Rychta Bretislav"
> <
RemoveMEBretislavRychtaTakeThisOuT
ALVISHAGGLUNDS.SE>
> To: <
spamBeGonePICLISTspamBeGone
MITVMA.MIT.EDU>
> Sent: Monday, April 28, 2003 11:48 PM
> Subject: SV: [PIC]: Frequency multiplier?
>
>
> The better way is to add 10 to input count and
> subtract 13 from output
> count. When output count underflow, toggle output
> pulse and ADD 'last pulse
> count' to output count.
> This approach don't need any further correction
> and allow you to easy change
> ratio of input and output frequency by changing
> only 2 constants.
> Run sequence on interrupt from timer to get
> constant sampling frequency
> which is in your case higher than 2*4000*13/10 Hz
> and lower than 2*200*65536/10 Hz (for 2-Byte
> counters)
>
> Breta
>
> -----Ursprungligt meddelande-----
> Fren: Bill & Pookie
> [
TakeThisOuTwilliamcornutt111EraseME
spam_OUTATTBI.COM]
> Skickat: mendag 28 april 2003 16:05
> Till:
RemoveMEPICLIST
TakeThisOuTMITVMA.MIT.EDU
> Dmne: Re: [PIC]: Frequency multiplier?
>
>
> Looking at the question as inputting a signal with
> a 50% duty cycle and outputting a signal 130%
> greater with a 50% duty cycle, here is my
> solution.
>
> Requires 4 routines,
>
> count input pulse width
> see if input changed
> decrement output count
> see if time to change output
>
>
> COUNT INPUT PULSE WIDTH
>
> In order to get the increase in frequency, the
> input count must be reduced before it becomes the
> count for the output. This is done by not
> counting the input pulse every forth time.
>
> The 'fourth input counter' will add a count to the
> input count to 'tweak it from 125% to 130% every
> 13th time it is called. The 52 (4*13) input
> timings results in 39 (3*13) input counts, and if
> 1 input count is added at this time, the
> percentage of 40 counts to 52 timings is 130%.
>
> SEE IF INPUT CHANGES
>
> When the input state changes, the input count is
> moved to the 'last pulse count' and the input
> pulse count is cleared. It may be a good idea to
> average the last pulse count and input pulse
> instead of just moving it. This is easily done by
> adding the two and right shifting the results.
> This averaging will encourage a 50% duty cycle for
> the output pulses.
>
> DECREMENT OUTPUT COUNT
>
> Just subtract one from output count.
>
> SEE IF TIME TO CHANGE OUTPUT
>
> if output count is zero, toggle output pulse and
> move 'last pulse count' to output count
>
> So there would be three series of
> count input pulse width
> see if input changed
> decrement output count
> see if time to change output
>
> And a fourth series with the 'count input pulse
> width' modified to only counting every 13th time.
>
> One main concept is that the input pulse and
> output pulse have no relationship in time except
> the 'last pulse count', and that count can change
> any time with the output routine using it when it
> toggles the output pulse and starts a new pulse.
>
> Bill
>
>
> ----- Original Message -----
> From: "Gary Neal" <
gln103EraseME
.....PSU.EDU>
> To: <
EraseMEPICLIST
MITVMA.MIT.EDU>
> Sent: Wednesday, April 23, 2003 6:08 PM
> Subject: [PIC]: Frequency multiplier?
>
>
> > Hi,
> >
> > I've got a variable frequency signal (200hz to
> 4khz) whose frequency I want
> > to increase by 30% (5v signal). IE if the input
> frequency is 1000hz, I
> > want to output 1300hz. Is there an easy method
> of doing this? I've heard
> > of PLL, but don't have a clue how to build them,
> so if there's an easier
> > option that would be great.
> >
> > Thanks,
> >
> > Gary
> >
> > --
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