using DSPF_sp_fftSPxSP in mcaspPlayBk example (Mcasp) issue

Mike%20Wang

I use LCDK6748 board and CCSv5.5 to do speech processing, my design modifies mcaspPlayBk.c program from C6748_StarterWare_1_20_04_01.

When do FFT/IFFT processing using dsplib kernel from dsplib_c674x_3_1_0_0, it generates ‘click’ noise due to interrupt. I found DSPF_sp_fftSPxSP is not interruptible. Could you please tell me where or how I could get interruptible FFT/IFFT kernel?

my design modifies mcaspPlayBk.c program from C6748_StarterWare_1_20_04_01. It uses EDMA, when buffer is filled, it generates interrupt. Basically it is package in and package out. When used buffer size 256, there is no click sound, when increase package size 512, 1024,… it starts generate bad click noise. Larger package size, worse noise.

Could you please help? this is McASP problem or FFT non-iterruptible problem? how to solve it?

over 11 years ago

0 Sivaraj Kuppuraj over 11 years ago

TI__Mastermind 35645 points

Hi Mike,

Thanks for your post.

Basically for an N-point FFT, if N=256, single pass implementation would be the best choice, but if you go beyong N-512, 1024 etc., you should go for multi-pass implementation (break-up large FFT's into several sub-FFT's). For more details on this, please refer Sections 3.3.3.1 & 3.3.3.2 the below doc.

http://www.ti.com/lit/an/spra947a/spra947a.pdf

Also, i don't think, it could be a interrupt problem, might be some buffer exceptions. Please refer the C67x DSP lib. programmer's reference guide to check the algorithm implementation in your code is compliant to the specified below doc.

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

In the above doc, please refer DSPF_sp_fftSPxSP function in page no. 49.

In addition to the above, please refer the below E2E threads which would give you better clarity:

http://e2e.ti.com/support/development_tools/compiler/f/343/t/185941.aspx

http://e2e.ti.com/support/dsp/tms320c6000_high_performance_dsps/f/115/t/95526.aspx

Thanks & regards,

Sivaraj K

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0 Mike%20Wang over 11 years ago in reply to Sivaraj Kuppuraj

Intellectual 640 points

Thanks Sivaraj! I re-check my program and will talk to you again.

This thread said DSPF_sp_fftSPxSP is not interruptible, some TI document says it is interruptible. What is your comment?

http://e2e.ti.com/support/dsp/tms320c6000_high_performance_dsps/f/115/p/12357/318933.aspx#318933

Best Regards,

Mike

0 Mike%20Wang over 11 years ago in reply to Mike%20Wang

Intellectual 640 points

Hi Sivaraj:

Unfortunately, I have not made it yet. I tried different ways. From following test, I think mcasp abstract physical layer holds too much time in mcaspPlayBk.c, and does not release time interval quickly from buffer to buffer when dealing with Tx /Rx, so it does not have enought time slot to do process, Please correct me if I am warong. If it is, please tel me which parameters in mcasp, I could twist so I can have longer processig time.

The following is my test to show my thought,

In mcaspPlayBk.c, when run loopback without do any processing as TI released, it works, Then still do loopback as exactly as before, just put real FFT /IFFT before

BufferTxDMAActivate(lastSentTxBuf, NUM_SAMPLES_PER_AUDIO_BUF,

(unsigned short)parToSend,

(unsigned short)parToLink);

to comsume computing cycles. it starts have 'click' noise.

// Real FFT of length N/2

for (j = 0; j < N / 2; j++)

{

pRFFT_In[2 * j] = (

float) buf_rx[2 * j]; //arrange real input sequence to

pRFFT_In[2 * j + 1] = (

float) buf_rx[2 * j + 1]; //N/2 complex sequence..

}

memcpy (pRFFT_InOrig, pRFFT_In, N * sizeof (float));

// Forward FFT Calculation using N/2 complex FFT..

DSPF_sp_fftSPxSP (N / 2, pRFFT_In, twiddle, pTemp, brev, rad, 0, N / 2);

// FFT Split call to get complex FFT out of length N..

FFT_Split (N / 2, pTemp, A, B, pRFFT_Out);

// Inverse FFT calculation

// IFFT Split call to get complex Inv FFT out of length N..

IFFT_Split (N / 2, pRFFT_Out, A, B, pTemp);

// Inverse FFT Calculation using N/2 complex IFFT..

DSPF_sp_ifftSPxSP (N / 2, pTemp, twiddle, pRFFT_InvOut, brev, rad, 0, N / 2);

0 Mike%20Wang over 11 years ago in reply to Mike%20Wang

Intellectual 640 points

Hi Sivaraj;

I wonder if you had a chance to look at my issue.

Thanks,

Mike

0 Sivaraj Kuppuraj over 11 years ago in reply to Mike%20Wang

TI__Mastermind 35645 points

Mike,

Ideally, as per TI doc, it is absolutely interruptible but there are few exceptions/known issues.

FYI, for our newer devices (674x core) we have released an updated DSPLIB:

http://wiki.davincidsp.com/index.php?title=C674x_DSPLIB

Please go through the below E2E threads for the known issues on some DSP Library functions:

There are attached IIR kernels (672xFilters.zip) written for c672x which might be useful in the below E2E thread (#12368)

http://e2e.ti.com/support/dsp/tms320c6000_high_performance_dsps/f/115/t/12368.aspx

http://e2e.ti.com/support/dsp/tms320c6000_high_performance_dsps/f/115/t/48070.aspx

Note: You need to disable interrupts before the DSP library function calls mentioned below and restore interrupts after, failing to do so, it will crash the application

DSPF_sp_minval
DSPF_sp_maxval
DSPF_sp_ifftSPxSP
DSPF_sp_dotprod
DSPF_sp_fir_gen
DSPF_sp_fir_r2

Thanks & regards,

Sivaraj K

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using DSPF_sp_fftSPxSP in mcaspPlayBk example (Mcasp) issue