Hello, 

I'm trying to implement a couple of IIR filters on a Blackfin BF537 DSP, my samples are 24bit
wide so the DSP functions included with VisualDSP++ are not good for me so I went to the
aplications notes and found EE-186 wich describe a 32 bit implementation for the IIR and FIR
filters but those IIR filters assume A0 to be iqual to 1.0
The problem is that I'm using MatLAB's FDATool to calculate the coefficients and it seems I can
not use them as they are. Can any one tell me what can I do to obtain the right coefficients?
(also how)

Thanks a lot in advance.

Juan Carlos Gálvez
       
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Hello Jon,

It seems I'm very confussed with all this fixed point stuff... I was looking closely the header
file now and the value of A0 is 
1073741824 which in hex format turns to be 0x40000000 and that is 1.0 in fixed point 2.30
format (in which I generated the coeff) so now the question is:
can I used the rest of the coeff and just ignore A0? (there is no place for A0 in the filter
function)

Thanks,

Juan Carlos Gálvez

----- Original Message ----
From: jon duncan <d...@yahoo.com>
To: Juan Carlos Galvez <j...@yahoo.com>
Sent: Tuesday, September 18, 2007 4:54:38 PM
Subject: Re: [adsp] IIR filter coefficients

Juan,
with fda tool you can export the coef using a c file with TI compser. What I have done in the
past is
export the coefs using the c file header with in the fda tool then copy and paste the coefs in
the visual dsp .
there is a new library within matlab that is made for the visualdsp++ but i have yet to spend
the 2000.00 for it.
Let me know if this helps or state specifically what the problem is.
 
Jon

----- Original Message ----
From: Juan Carlos Galvez <j...@yahoo.com>
To: a...@yahoogroups.com
Sent: Tuesday, September 18, 2007 12:57:57 PM
Subject: [adsp] IIR filter coefficients

Hello, 
 
I'm trying to implement a couple of IIR filters on a Blackfin BF537 DSP, my samples are 24bit
wide so the DSP functions included with VisualDSP++ are not good for me so I went to the
aplications notes and found EE-186 wich describe a 32 bit implementation for the IIR and FIR
filters but those IIR filters assume A0 to be iqual to 1.0
The problem is that I'm using MatLAB's FDATool to calculate the coefficients and it seems I can
not use them as they are. Can any one tell me what can I do to obtain the right coefficients?
(also how)
 
Thanks a lot in advance.
 
Juan Carlos Gálvez

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On Tue, 18 Sep 2007, Juan Carlos Galvez wrote:

> Hello Jon,
>
> It seems I'm very confussed with all this fixed point stuff... I was looking closely the
header file now and the value of A0 is
> 1073741824 which in hex format turns to be 0x40000000 and that is 1.0 in fixed point 2.30
format (in which I generated the coeff) so now the question is:
> can I used the rest of the coeff and just ignore A0? (there is no place for A0 in the
filter function)

You don't have to multiply by 1, but you have to include the term being
multiplied.  If the filter function does that, then you can "ignore" A0
with no problem.

Patience, persistence, truth,
Dr. mike

Thanks Mike for your answer, well, yes, the function does the multiply operation for me,
there is no place for the A0 coeff among the arguments.
One more question, I calculated (MatLAB calculated) the coeff using the 2.30 fixed point format
to gain in precision (I followed an example on the book "embedded signal
processing.....") now, the processor arithmetics is 1.31 so if I use the coeff as they are
the processor will see half the intended value... so, should I scale up all the coeff by 2
before I use them on the filter function?
 
Already have patience and persistence.... but still a long way to truth... ;)
----- Original Message ----
From: Mike Rosing <e...@eskimo.com>
To: Juan Carlos Galvez <j...@yahoo.com>
Cc: a...@yahoogroups.com
Sent: Wednesday, September 19, 2007 9:53:05 AM
Subject: Re: [adsp] IIR filter coefficients
On Tue, 18 Sep 2007, Juan Carlos Galvez wrote:

> Hello Jon,
>
> It seems I'm very confussed with all this fixed point stuff... I was looking closely the
header file now and the value of A0 is
> 1073741824 which in hex format turns to be 0x40000000 and that is 1.0 in fixed point 2.30
format (in which I generated the coeff) so now the question is:
> can I used the rest of the coeff and just ignore A0? (there is no place for A0 in the
filter function)

You don't have to multiply by 1, but you have to include the term being
multiplied.  If the filter function does that, then you can "ignore" A0
with no problem.

Patience, persistence, truth,
Dr. mike
       
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