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sinewave generation

Started by Girish ●March 31, 2004
Hai all ,

I am trying to generate a sine wave from the look up
table on ADSP-2181(Fixed point processor).Even i am
able to get the wave form of desired frequency but
the problem is tht i am unable to get the proper shape
of sine wave at the peaks. That is peak is getting
truncated and becoming flat(at both peaks).

What is the reason for tht ? and how can i
over come the same.
waiting for reply from many. Thanks and regards

Bye
Girish

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Reply by Leon Heller ●March 31, 20042004-03-31

----- Original Message -----
From: "Girish" <>
To: <>
Sent: Wednesday, March 31, 2004 7:35 AM
Subject: [adsp] sinewave generation > Hai all ,
>
> I am trying to generate a sine wave from the look up
> table on ADSP-2181(Fixed point processor).Even i am
> able to get the wave form of desired frequency but
> the problem is tht i am unable to get the proper shape
> of sine wave at the peaks. That is peak is getting
> truncated and becoming flat(at both peaks).
>
> What is the reason for tht ? and how can i
> over come the same.

You must be calculating the values wrong, so that the amplitude is too high
and the waveform is getting clipped.

Leon



Reply by himanshu dwivedi ●March 31, 20042004-03-31

Hi Girish,

I guess u need to check the register values , as u r working on 2181 ..and there is probs of circular buffering .. if u have not taken the circular buffer as multiple of two then the values will overwrite in ur registers , that will change the shape of ur sine wave ...
u just monitor the registers u will come to know ..

What leon said that can also b true ..just check that u r calculating the correct value..

Thanks & Regards
Himanshu Dwivedi On Wed, 31 Mar 2004 Leon Heller wrote :
>
>----- Original Message -----
> From: "Girish" <g...@yahoo.com>
>To: <a...@yahoogroups.com>
>Sent: Wednesday, March 31, 2004 7:35 AM
>Subject: [adsp] sinewave generation > > Hai all ,
> >
> > I am trying to generate a sine wave from the look up
> > table on ADSP-2181(Fixed point processor).Even i am
> > able to get the wave form of  desired frequency but
> > the problem is tht i am unable to get the proper shape
> > of sine wave at the peaks. That is peak is getting
> > truncated and becoming flat(at both peaks).
> >
> >            What is the reason for tht ? and how can i
> > over come the same.
>
>You must be calculating the values wrong, so that the amplitude is too high
>and the waveform is getting clipped.
>
>Leon >_____________________________________
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Reply by Mike Rosing ●March 31, 20042004-03-31
On Wed, 31 Mar 2004, [iso-8859-1] Girish wrote:

> I am trying to generate a sine wave from the look up
> table on ADSP-2181(Fixed point processor).Even i am
> able to get the wave form of desired frequency but
> the problem is tht i am unable to get the proper shape
> of sine wave at the peaks. That is peak is getting
> truncated and becoming flat(at both peaks).
>
> What is the reason for tht ? and how can i
> over come the same.
> waiting for reply from many.
>

It's not clear to me if it's the analog section that's clipping or the
digital. If it's digital, then check the saturation bit. You're getting
overflow somehow. If it's analog, then fix the dac so you have the full
range of values for voltage generation.

As Carl von Clausewitz said, even the simplest things are complicated.
Look up tables are simple. There's just a lot of detail to watch out for!

Patience, persistence, truth,
Dr. mike

Reply by Prasanna Nambi ●March 31, 20042004-03-31
Hi,
Is there any specific reason for look up table
implementation? u don'nt need to do this on a DSP
similar to a uController.
U can as well do a sine generation using the standard
Taylor series expansion as suggested by ADI.The DSP
can easily do this because of its MAC and barrel
shifter architecture .u can change the frequecny @ any
time by changing the delta reference.refer ADI
,Application manual ,Sine wave generation that is
proven.
Regards
Prasanna
--- Girish <> wrote:
> Hai all ,
>
> I am trying to generate a sine wave from the look up
> table on ADSP-2181(Fixed point processor).Even i am
> able to get the wave form of desired frequency but
> the problem is tht i am unable to get the proper
> shape
> of sine wave at the peaks. That is peak is getting
> truncated and becoming flat(at both peaks).
>
> What is the reason for tht ? and how can
> i
> over come the same.
> waiting for reply from many. > Thanks and regards
>
> Bye
> Girish ________________________________________________________________________
> Yahoo! Messenger - Communicate instantly..."Ping"
> your friends today! Download Messenger Now
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> _____________________________________
> Note: If you do a simple "reply" with your email
> client, only the author of this message will receive
> your answer. You need to do a "reply all" if you
> want your answer to be distributed to the entire
> group.
>
> _____________________________________
> About this discussion group:
>
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Reply by Jaime Andres Aranguren Cardona ●April 1, 20042004-04-01
Is your LUT well shaped? If things like the freq are
ok, some reasons could be that the values in your
table are too big for the DSP / DAC to be well
represented, or that definitely your table is not well
shaped.

JaaC

--- Prasanna Nambi <> wrote:
> Hi,
> Is there any specific reason for look up table
> implementation? u don'nt need to do this on a DSP
> similar to a uController.
> U can as well do a sine generation using the
> standard
> Taylor series expansion as suggested by ADI.The DSP
> can easily do this because of its MAC and barrel
> shifter architecture .u can change the frequecny @
> any
> time by changing the delta reference.refer ADI
> ,Application manual ,Sine wave generation that is
> proven.
> Regards
> Prasanna
> --- Girish <> wrote:
> > Hai all ,
> >
> > I am trying to generate a sine wave from the look
> up
> > table on ADSP-2181(Fixed point processor).Even i
> am
> > able to get the wave form of desired frequency
> but
> > the problem is tht i am unable to get the proper
> > shape
> > of sine wave at the peaks. That is peak is getting
> > truncated and becoming flat(at both peaks).
> >
> > What is the reason for tht ? and how
> can
> > i
> > over come the same.
> > waiting for reply from many.
> >
> >
> > Thanks and regards
> >
> > Bye
> > Girish
> >
> >
> >
> >
> >
>
________________________________________________________________________
> > Yahoo! Messenger - Communicate instantly..."Ping"
> > your friends today! Download Messenger Now
> > http://uk.messenger.yahoo.com/download/index.html
> >
> >
> >
> > _____________________________________
> > Note: If you do a simple "reply" with your email
> > client, only the author of this message will
> receive
> > your answer. You need to do a "reply all" if you
> > want your answer to be distributed to the entire
> > group.
> >
> > _____________________________________
> > About this discussion group:
> >
> > To Join: Send an email to
> >
> >
> > To Post: Send an email to
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> >
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> >
> >
> >
> >
> >
> > __________________________________ >
>
> _____________________________________
> Note: If you do a simple "reply" with your email
> client, only the author of this message will receive
> your answer. You need to do a "reply all" if you
> want your answer to be distributed to the entire
> group.
>
> _____________________________________
> About this discussion group:
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=====

Jaime Andr Aranguren Cardona

__________________________________