CCS/TMS320F28379D: How to make the example code "2837x_RFFT_ADC" work in standalone for getting the accurate FFT output

Mohammad Arifur Rahman83

Part Number: TMS320F28379D

Tool/software: Code Composer Studio

Hello,

I was working with the example code "2837x_RFFT_ADC" for doing FFT in the ADC output. If I am not wrong; when the code is being executed the sequence should be like this:

1) ADC output is kept in RFFTin1Buff

2) FFT is done on the RFFTin1Buff data and FFT output is kept in the RFFToutBuff

3) RFFT32Coef and RFFTmagBuff data are calculated from the RFFToutBuff.

When I was running the code in "Debug" mode, everything is working properly. But when I am trying to make it work in standalone, the RFFTin1Buff data seems to be ok but the RFFToutBuff data are becoming very small (Close to zero). Also the RFFT32Coef data are becoming exactly zero and the RFFTmagBuff data are also close to zero. For the RFFT32Coef and RFFTmagBuff, I am guessing that since they are being calculated from the RFFToutBuff and since the RFFToutBuff is not ok in the standalone mode, that's why RFFT32Coef & RFFTmagBuff are not ok. So the problem seems to be in getting the accurate RFFToutBuff data in standalone mode.

In this case how can I solve this problem so that I can get the accurate RFFToutBuff, RFFT32Coef and RFFTmagBuff in standalone mode??

Thanks

Mohammad Arifur Rahman

over 8 years ago

0 Richard Poley over 8 years ago

TI__Mastermind 27200 points

Mohammad,

On my machine I had to define the symbol FLASH in two places. In the project properties:

C2000 Compiler -> Advanced Options -> Predefined symbols

C2000 Linker -> Advanced Options -> Command File Preprocessing

Could you just confirm you've done both these ? Thanks.

Regards,

Richard

0 Mohammad Arifur Rahman83 over 8 years ago in reply to Richard Poley

Intellectual 840 points

Thanks for your reply. Flash was defined in both cases. But still it did not work properly in the standalone mode.

Mohammad Arifur Rahman

0 Vishal_Coelho over 8 years ago in reply to Mohammad Arifur Rahman83

TI__Mastermind 20850 points

Its very odd that RFFT32Coef has 0 valued entries. The problem originates from that since the FFT gets the twiddle factors from that array; if they are 0 the output will be zero and subsequently the mag and phase will also be 0.

In the example the twiddle factors are calculated at runtime,

    RFFT_f32_sincostable(hnd_rfft);        //Calculate twiddle factor

After this function is run is RFFT32Coef 0 or is it zeroed out at a later point. Also did you get any build warnings?

0 Mohammad Arifur Rahman83 over 8 years ago in reply to Vishal_Coelho

Intellectual 840 points

Vishal, thanks for your reply.

I have solved the problem. I had to include the "RFFT_f32_sincostable.c" file in the project and made a little bit change in the main code. Now it's working.

Thanks

Mohammad Arifur Rahman

C2000™︎ microcontrollers

C2000 microcontrollers forum

CCS/TMS320F28379D: How to make the example code "2837x_RFFT_ADC" work in standalone for getting the accurate FFT output