C6748 LCDK Issue real time sampling and fft

Daniel Medina

Other Parts Discussed in Thread: OMAP-L138

Hello,

I've been trying to use the C6748 LCDK to take a number of real time samples, take the fft of this and then do some processing to the fft. To do this I have been using the microphone input and following some of the examples found in "Digital Signal Processing and Applications with the OMAP-L138 experimenter", believe I have the sampling working correctly. However, I need to take around 8000 samples and when I try to use any of the fft functions, either the ones used in the book or ones from the dsp libraries, it will get stuck. After playing around for a while, I figured out that it only does this for high number of input samples, if I take only 32 it will go through but anything larger than that makes it stop working. So my guess is I am somehow using the fft functions wrong or could be something else basic that i am missing. I have very little experience using DSP's, so I am very unfamiliar with them. Any help would be appreciated.

-Daniel

over 12 years ago

0 nikunj.rudani over 12 years ago

Expert 1990 points

Any snap of your code or error will guide to understand your problem from depth.

0 Sivaraj Kuppuraj over 12 years ago

TI__Mastermind 35645 points

Hi Daniel,

Thanks for your post.

TI supports C674x DSP library packages in which you shall compute CPU cycle time for a N-point FFT. You shall download the DSPLIB package (dsplib_c674x_3_1_0_0) in the below link:

http://software-dl.ti.com/sdoemb/sdoemb_public_sw/dsplib/latest/index_FDS.html

There are sample project examples provided in the package installation path as below:

~\dsplib_c674x_3_1_0_0\packages\ti\dsplib\src\DSPF_sp_fftSPxSP\c674

Please refer the above path to run the complex FFT driver code which tests the kernel and reports the CPU cycle count measurements for a N-point FFT computation.

In addition to the above, please refer DSP library function (DSPF_sp_fftSPxSP), page no. 49 for its usage, in the TMS320C67x DSP Library Programmer’s Reference Guide as below:

http://www.ti.com/lit/ug/spru657c/spru657c.pdf

Also, please refer the below E2E post for more info. on calculating time elapsed in finding the max. sampling frequency:

http://e2e.ti.com/support/dsp/omap_applications_processors/f/42/t/182534.aspx

I hope it addresses your query.

Thanks & regards,

Sivaraj K

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C6748 LCDK Issue real time sampling and fft