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


From: Sander Pool
Subject: Re: [avr-gcc-list] sine wave generator. ~~~
Date: Fri, 26 Jul 2002 11:57:06 -0700

Well, the main benefit of a software solution is that it can be changed much
more easily than a PCB so I wouldn't give up on a software solution just
yet! In fact I wouldn't classify this behavior as 'lazy', it's widespread in
all kinds of electronic devices and the real reason micro controllers are so
wide spread.

    Sander

----- Original Message -----
From: "Marlin Unruh" <address@hidden>
To: "David Snowdon" <address@hidden>
Cc: <address@hidden>
Sent: Friday, July 26, 2002 8:31 AM
Subject: Re: [avr-gcc-list] sine wave generator. ~~~


> David,
>
> Sometimes I get lazy and think software is the easiest way to fix things.
I
> have ample PCB real estate so that isn't a valid excuse. I think you are
> right with the R2R network scheme. I believe that is the direction I will
> take. The R2R network, it would seem to me, would be the most stable
> solution considering temperature.
>
> Thank you for sharing your thoughts.  :-)
>
> Marlin
>
> At 12:04 AM 7/27/2002 +1000, you wrote:
> >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
>
> avr-gcc-list at http://avr1.org
>

avr-gcc-list at http://avr1.org



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