dsp进行复数fft运算出现NaN怎么回事？如何解决

Question

ccs环境下用DSPF-sp_fftSPxSP()函数进行复数FFT运算但是结果是NaN。请问如何解决？

Answer 1

https://e2e.ti.com/support/processors/f/processors-forum/281205/nan-output-with-fft-using-dsplib

To start with, there is a demonstration app. (DSPF_sp_ifftSPxSP_d.c) for DSPF_sp_ifftSPxSP kernel in the DSP library package which is a complex inverse FFT with mixed radix driver code tests the kernel and reports the benchmark results of CPU cycles (Success/Failure). If you run this project first, you will be able to validate the usage of this kernel in your scenario which is in the installation path as below:

~\dsplib_c674x_3_1_0_0\packages\ti\dsplib\src\DSPF_sp_ifftSPxSP\c674\DSPF_sp_ifftSPxSP_674LE_LE_COFF

Next, please refer the below wiki for the C674x DSPLIB Known issues for DSPF_sp_ifftSPxSP kernel:

http://processors.wiki.ti.com/index.php/C674x_DSPLIB_Known_Issues#DSPF_sp_fftSPxSP_and_DSPF_sp_ifftSPxSP_Functions_Overwrite_the_Input_Buffer

Also, please refer the below E2E thread for the similar usecase as yours which would give you an idea on the impact of DSPLINK intervention with the dsplib but it is for OMAP3530 EVM and

http://e2e.ti.com/support/embedded/bios/f/355/p/150484/559542.aspx#559542

As per your usecase, there could be many possibilities but please make sure that the DSP and ARM are exchanging same input and output data through DSPLINK. You can exchange checksum data on both ARM & DSP to ensure the same.

1. Probem could be with the usage of dsplib function for IFFT

2. It could be the data mismatch between ARM and DSP through IPC

3. Issue could be with the array/buffer size between ARM and DSP through DSPLINK

4. might be a scaling range issue

Please also refer the below wiki to get an idea on how to debug the dsp side of a dsplink application,

http://processors.wiki.ti.com/index.php/Debugging_the_DSP_side_of_a_DSPLink_application_on_OMAP_using_CCS#Modify_the_DSPLink_message_example

I also recommend you to refer the DSPLINK API documentation which would be in the dsplink source installation path as below:

~/dsplink_1_xx_xx_xx/dsplink/doc/source_documentation/html/index.html