Re: [avr-gcc-list] sine wave generator. ~~~

[Sander Pool]

I forgot to add that there is an appnote on the Atmel site that shows how to
generate telephone dail tones using a lookup table and built-in PWM.

    Sander

----- Original Message -----
From: "David Snowdon" <address@hidden>
To: "Marlin Unruh" <address@hidden>
Cc: "Peter Bosscha" <address@hidden>; <address@hidden>
Sent: Friday, July 26, 2002 7:04 AM
Subject: Re: [avr-gcc-list] sine wave generator. ~~~


> G'Day Marlin,
>
> Doing that would be essentially the same as PWM. You're just adjusting
> the duty cycle of a waveform, which is then converted into an analogue
> voltage via a low pass filter.
>
> The easiest way, in my mind, would be the R2R network. But... If you'd
> like to do the LPF thing, I'd go with PWM. You just have to choose your
> PWM frequency high enough that its a fair bit higher than your maximum
> output frequency. Then you have to choose your LPF cutoff such that it
> will pass your maximum output frequency, but attenuate the PWM
> frequencies.
>
> Talk to you soon,
>
> Dave.
>
> On Friday, July 26, 2002, at 10:35 PM, Marlin Unruh wrote:
>
> > Peter,
> >
> > The R2R ladder network was one thing I was thinking about. Then use a
> > lookup table of values to place on the port connected to the R2R
> > network at a given time duration. This may be the solution.
> >
> > I was also wandering if I could use the SPI output pin and shift out
> > bit patterns and run them through a RC filter. If you sent out a series
> > of zeros the voltage would go to ground, or a series of ones the
> > voltage would go to VCC. If you keep shifting out 10101010 thru the RC
> > filter the voltage would go to VCC/2, with some ripple. The RC filter
> > would need to be matched to the clock rate on the SPI MOSI pin. This
> > may not take that much overhead for the processor depending on the
> > clock rate of the SPI. I would use the SPI data register empty
> > interrupt to feed the SPI data register.
> >
> > Does that sound stupid? Although for me it would cause some problem
> > because I need the SPI port to communicate with another micro
> > controller on the same PCB. I will have to think about it.
> >
> > Thanks again.  :-)
> >
> > Marlin
> >
> >
> > At 07:41 AM 7/26/2002 +0200, you wrote:
> >> How about this:
> >>
> >> http://www.myplace.nu/avr/minidds/
> >>
> >> Always been meaning to try it out :-)
> >>
> >> >>> Marlin Unruh <address@hidden> 07/26/02 03:51AM >>>
> >> Hi,
> >>
> >> I am needing to generate a sine wave using an AVR. The sine wave needs
> >> to
> >> change in frequency between 1500Hz to 5500Hz approx. Is there a mostly
> >>
> >> digital solution? I could use an AVR that basically had nothing else to
> >> do
> >> but read a port as input and generate the sine wave. Using a resistor
> >> and
> >> capacitor on the PWM output for a wave shaper really wouldn't work
> >> because
> >> the frequency isn't constant. Right?
> >>
> >> I have several ideas,but think I am making it more complex that it
> >> really is.
> >>
> >> I hope I'm not abusing this forum with this question!
> >>
> >> Any pointers would be appreciated.
> >>
> >> Marlin
> >>
> >> avr-gcc-list at http://avr1.org
> >>
> >> avr-gcc-list at http://avr1.org
> >
> > avr-gcc-list at http://avr1.org
> >
>
> avr-gcc-list at http://avr1.org
>

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