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Problem with arm_cfft_f32()

Note: This was originally posted on 27th August 2013 at http://forums.arm.com

Hello,

I'm new in the field of ARM and I need some help. I try to make a FFT on a Cortex-M4 with fpu. I tried two examples given with the CMSIS library, an old one which uses arm_cfft_radix4_f32() and a new one with arm_cfft_f32(). The two examples compile well. The old code with arm_cfft_radix4_f32() works quite good. That function is deprecated so I would like to use arm_cfft_f32() but I don't get the right data at the end.

The program makes a FFT of a given signal and should detect the peak in magnitude at refIndex = 213. It's ok with the deprecated function arm_cfft_radix4_f32() but not with arm_cfft_f32(). I get refIndex = 861. I tried to change the 'doBitReverse' value from 1 to 0 but nothing changed I have exactly the same result at the output of arm_cfft_f32().

I didn't find the same issue on the web. Is there a known problem with arm_cfft_f32() ? Could someone explain me what I'm doing wrong ?

Thanks,
Pierre.

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Daniel White over 11 years ago in reply to FS

Hi frsc,
I think ST just needs to offer the more up-to-date versions of CMSIS. This should be fixed in the version offered by ARM. I forget which version specifically that this got patched, but it has been fixed.
CMSIS - Cortex Microcontroller Software Interface Standard - ARM
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Daniel White over 11 years ago in reply to FS

Hi frsc,
I think ST just needs to offer the more up-to-date versions of CMSIS. This should be fixed in the version offered by ARM. I forget which version specifically that this got patched, but it has been fixed.
CMSIS - Cortex Microcontroller Software Interface Standard - ARM
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Ibrahim ERTURK over 10 years ago in reply to Daniel White

Hi, I'm in trouble with the CMSIS DSP library (on STM32F429) regarding bitreversal function and solved it the workaround described here. Hope this helps.
Regards
Ibrahim
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Daniel White over 10 years ago in reply to Ibrahim ERTURK

Hello Ibrahim,
Can you tell me the version # at the top of the arm_bitreversal.c file you are using?
Thanks,
Dan
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Ibrahim ERTURK over 10 years ago in reply to Daniel White

Hi Daniel,
It is "$Revision: V1.4.1" supplied by ST.
Regards,
Ibrahim
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Daniel White over 10 years ago in reply to Ibrahim ERTURK

Hello Ibrahim,
I have passed on your information to the appropriate people at ARM. In the mean time, you are using a bit older version of CMSIS. (3 versions old).
You can download the newest one here:
http://www.arm.com/products/processors/cortex-m/cortex-microcontroller-software-interface-standard.php
Also, when I looked at your website, you mention you're using the Cortex M4 with fpu, but the library file you're including is “libarm_cortexM4l_math.a”, there should be a version “libarm_cortexM4lf_math.a” available to you that is for Cortex M4's with an FPU. You should notice dramatic performance increases if you're using floating-point functions.
Hopefully the newest version of CMSIS doesn't have the same missing function issue. Likely it was just a mistake when compiling it. Please do let us know if you run into the same problem on the newer version though.
Cheers,
Dan
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Ibrahim ERTURK over 10 years ago in reply to Daniel White

Hi Dan,
Thanks for your interest. Yes, the CMSIS version I'm using is a bit older, because this is the DSP library for SM32F4 supplied by ST. It can be downloaded from ST website. I'll try the new version of CMSIS DSP library and let you know the results.
Regarding floating point library “libarm_cortexM4lf_math.a”, I've already used for FFT functions, and it is obvious that the performance increases.
Best regards,
Ibrahim
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Ibrahim ERTURK over 10 years ago in reply to Ibrahim ERTURK

Hi Dan,
I've tried the latest CMSIS DSP library "libarm_cortexM4lf_math.a" (Date 12. March 2014, Revision V1.4.4), and everything works fine.
Thanks.
Regards,
Ibrahim
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amel over 10 years ago in reply to Ibrahim ERTURK

Hi Ibrahim & Dan,
It is already planned to embed the new CMSIS DSP Library V1.4.4 in the next STM32F4 Standard Peripheral Library release.
Please note that the DSP library will be also available in the next release of STM32CubeF4 package.
Best Regards,
Amel
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