You have to copy your samples into get_inbuf() first. That's where FFTW
expects the data. *dst is just a convenience variable to allow for less
typing. Instead of:
memcpy(ofdm_fft.get_inbuf(), in, sizeof(gr_complex) * ofdm_fft_size);
You can use:
memcpy(dst, in, sizeof(gr_complex) * ofdm_fft_size);
Ron
On 12/23/21 10:42 AM, George Edwards wrote:
Hi Ron,
Sorry for bothering some more!
In Debugging it appears that dst is not pointing to the input data
(input_items[0]), which we pointed to with pointer variable inat the
start of the work(...)method
(constgr_complex*in = (constgr_complex*) input_items[0];
Here is a snippet of my Debugging code and the values I see in ge_in =
dst[i] while single stepping through the code are all zeros.
gr_complex * dst; // copy from your code:
dst = ofdm_fft.get_inbuf(); //copy from your code
//****** my debug code starts **********
gr_complex ge_in;
for(int i = 0; i < 8; i++) // I am inputting 8 samples
{
ge_in = dst[i]; // extracting the values in dst
shows zero's
}
// ******my debug code ends *********
It appears that setting dst = ofdm_fft.get_inbuf() is not pointing to
the actual input samples values.
I did not see anywhere in your code where there is an explicit binding
between in and get_inbuf().
I will appreciate it if you can help me here!
Thank you!
George
On Wed, Dec 15, 2021 at 12:32 AM Ron Economos <w...@comcast.net
<mailto:w...@comcast.net>> wrote:
FFT support is built in to GNU Radio with FFTW. Here's how it's
done. First, define it in your foo_impl.h file. The options are
fft_complex_fwd, fft_complex_rev, fft_real_fwd and fft_real_rev.
https://github.com/drmpeg/gr-paint/blob/master/lib/paint_bc_impl.h#L25
<https://github.com/drmpeg/gr-paint/blob/master/lib/paint_bc_impl.h#L25>
https://github.com/drmpeg/gr-paint/blob/master/lib/paint_bc_impl.h#L41
<https://github.com/drmpeg/gr-paint/blob/master/lib/paint_bc_impl.h#L41>
Then initialize it in your foo_impl.cc constructor.
https://github.com/drmpeg/gr-paint/blob/master/lib/paint_bc_impl.cc#L47
<https://github.com/drmpeg/gr-paint/blob/master/lib/paint_bc_impl.cc#L47>
Then execute it.
https://github.com/drmpeg/gr-paint/blob/master/lib/paint_bc_impl.cc#L175-L179
<https://github.com/drmpeg/gr-paint/blob/master/lib/paint_bc_impl.cc#L175-L179>
You'll need to add the component in the top level CMakeLists.txt.
https://github.com/drmpeg/gr-paint/blob/master/CMakeLists.txt#L78
<https://github.com/drmpeg/gr-paint/blob/master/CMakeLists.txt#L78>
And link with it in lib/CMakeLists.txt
https://github.com/drmpeg/gr-paint/blob/master/lib/CMakeLists.txt#L25
<https://github.com/drmpeg/gr-paint/blob/master/lib/CMakeLists.txt#L25>
If you need a window, you can look at the block implementation
file for details.
https://github.com/gnuradio/gnuradio/blob/master/gr-fft/lib/fft_v_fftw.cc
<https://github.com/gnuradio/gnuradio/blob/master/gr-fft/lib/fft_v_fftw.cc>
Ron
On 12/14/21 7:53 PM, George Edwards wrote:
Dear GNURadio Community:
I am writing a C++ OOT block where the signal processing requires
the computation of both fft and ifft. Is there any Gnuradio C++
functions for the fft and ifft? If not, is there any way to wrap
in Python's libraries with these methods into C++ OOT?
Thank you!
Regards,
George
