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Original question:

CCS/TMS570LS1224: Problem when performing FFT on MCU

CCS/TMS570LS0432: CMSIS fft example on hercules TMS570LS0432

Aditi Mishra
Prodigy 160 points
Part Number: TMS570LS0432
Other Parts Discussed in Thread: TMS570LS3137, , TMS570LS0714

Tool/software: Code Composer Studio

Hi,

I am trying to run the example fft program. I was able to build it but the fft coefficients don't match the coefficients that I get from python. Could you please help me understand why this would be happening?

Thanks,

Aditi

  • 0
    TI__Mastermind 49120 points

    Hi Aditi,

    The FFT example included as part of this library was made for TMS570LS3137, which includes a floating-point coprocessor (FPU). TMS570LS0432 does not include an FPU. If you want to run this demo app on the LS0432, you will need to switch the *_f32 function calls to the equivalent q15 or q31 calls.

    Regards, Sunil

  • 0 in reply to Sunil Oak
    Prodigy 160 points

    Hey Sunil, 

    Thanks for the quick reply. I changed the controller to TMS570ls0714 now which has a floating point unit but my coefficients are still not matching.

    1st 10 coefficients from python scipy fft function:

    [89.44594621 26.10347899 35.74695852 34.72211329 49.24308138 55.42077977, 89.12154401 20.61311953 37.02841014 98.74230258]

    1st 10 coefficients from arm_fft_bin_example_f32.c :

    [89.4459534, 86.5393677, 123.025108, 123.025108, 36.562748, 31.8825817, 31.8825817, 36.562748, 71.3714828, 33.555027]

    *edit: changed bitreversal to 1, now the coefficients match.

    Regards,

    Aditi