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From: khan Sim on 14 May 2010 05:33
Hi, i have made a model in simulink and want to generate the verilog code for the model.

i have used an embedded matlab block named as Embedded MATLAB Function3

when i run the compatibilty checker i get no errors but when i run the generate code, i get the following errors

..
Code generation failed Call to unsupported function (cos) detected.

Function 'eml_scalar_cos' (#43.138.148), line 8, column 9
Function 'cos' (#42.298.318), line 10, column 12
Function 'eml_fft' (#39.4114.4124), line 122, column 28
Function 'eml_fft' (#39.1969.2000), line 52, column 5
Function 'eml_fft' (#39.1840.1869), line 47, column 10
Function 'fft' (#49.278.306), line 9, column 5
Function 'Embedded MATLAB Function3' (#19.46.65), line 3, column 14

i hope there is no imbiguity in code understanding ,

kindly help me out , how can i remove these errors???

and generate HDL succesfully???

urgent help required,
kind regards
From: Sean Little on 14 May 2010 11:31
You have work to do.

The problem you are experiencing happens because you are using functions in EML that are not supported for HDL code generation. Neither the COS or FFT functions can be converted directly to Verilog in the HDL Coder.

Instead, you will need to break up your EML design and use the HDL FFT block from the HDLDEMOLIB library. You will also need to use an approximation for the COS function. The cordic algorithm might work for you. See the following doc link:

http://www.mathworks.com/access/helpdesk/help/toolbox/simulink/slref/trigonometricfunction.html

I do hope you are using fixed point, right?

Sean Little
From: khan Sim on 15 May 2010 12:45
thank you very much Mr Sean for your time,


well i am not using fixed point tool box, i have made a simulink model and used the embedded function block.

Kindly guide me what is the role of fixed point tool box in the HDL code generation process???

and i can send you the code via your email, for your future guidance. cuz i see very little people having expertise in HDL and simulink.

waiting for your reply

thanx.
From: khan Sim on 15 May 2010 15:02
the the embedded function block has the following code,

i hope you may guide me after looking at this code

function smb = fcn(sb,sb0)
%#eml
fsb=fft(sb);
fsb0=fft(sb0);
% Power equalization%
amp_max=1/sqrt(2); % Maximum amplitude for equalization
afsb0=abs(fsb0);
P_max=max(afsb0);
for k = 1:length(fsb0)
if afsb0(k) > amp_max*P_max
fsb0(k) = (amp_max*(P_max^2)./afsb0(k)).*exp(1j*angle(fsb0(k)));
end
end
fsmb=fsb.*conj(fsb0);%
% Inverse Fourier Transform%
smb=fftshift(ifft(fftshift(fsmb.'))).';

i am not using cos function anywhere in the code.

waiting for reply
regards
khan
From: Sean Little on 17 May 2010 10:36
For HDL code to be synthesizable, you must use fixed point. The code you
posted is using double precision data. The HDL Coder *might* produce Verilog
from this EML (assuming you either write your own FFT, EXP, SQRT, IFFT,
FFTSHIFT functions or find compatible implementations), but the result would
not be useful in ANY practical sense. The reason is that you are developing
hardware here, not software. An FPGA has no way to handle floating point
data like a normal software program would. You must therefore use fixed
point if you intend to synthesize this design.

You must do the following:

1) Find/write an HDL compatible implementation for FFT, EXP, 1/SQRT, IFFT,
FFTSHIFT. I have some approximation utilities that might be useful. I have
been planning on posting those to the file exchange for a while, and I will
try to do that this week. That would help with EXP and 1/SQRT. For your FFT
implementation, I would point you to the "eml_hdl_design_patterns.mdl" demo
that ships with the HDL Coder. Note that once you have an FFT, the IFFT is
just an FFT with a conjugate scale factor.

2) Convert your code to use fixed point.

This is a very interesting project, but both those steps will require
significant time and effort. I recommend lots of careful unit testing. If
you have access to the EDA simulator link, your task will be easier.

If you have specific questions, please post here.

Sean Little


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