CCS/LAUNCHXL-F28379D: F28379D ADC output data of RFFT_ADC (DSP library)

naveenkumar buduru

Tool/software: Code Composer Studio

Hi sir,

I am using RFFT_ADC (DSP Library) for finding FFT of the signal. I connected a 50Hz sinusoidal signal to J3, Pin30 of the launchpad of F28379D and J3, GND to external circuit ground. I am not getting sinusoidal output, here i attaching the result. What might be the reason?

over 7 years ago

0 Richard Poley over 7 years ago

TI__Mastermind 27200 points

It looks like you have selected the wrong data type to display the graph. In CCS, check the Q value in graph properties. If you select Q0 (i.e. clear the Q value) you should be displaying the raw unsigned integer data from the ADC.

Regards,

Richard

0 naveenkumar buduru over 7 years ago in reply to Richard Poley

Intellectual 650 points

Hi Sir,

This are the following graph settings are made in ccs.

This is the corresponding Graph

Question: Why RFFTin1Buff is [2*RFFT_SIZE] and RFFToutBuff [RFFT_SIZE]. The ADC output is real valued signal that will be stored in RFFTin1Buff and output of RFFT_ADC (DSP Library) should be complex. So the sizes should be in opposite, i.e RFFTin1Buff is [RFFT_SIZE] and RFFToutBuff[2*RFFT_SIZE]

0 naveenkumar buduru over 7 years ago in reply to naveenkumar buduru

Intellectual 650 points

Respected sir,

Please answer for the above question.

0 Vishal_Coelho over 7 years ago

TI__Mastermind 20850 points

which buffer are you plotting? I would bypass the calculation of the FFT and just sample the input and see if you can get a distortion free representation of your signal.

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CCS/LAUNCHXL-F28379D: F28379D ADC output data of RFFT_ADC (DSP library)