I noticed that the stock firmware uses both the standard (double) and float FFTW3 libraries. The install instructions have you build both library versions. It looks like the float libraries are only used in fft_filter.c, the standard libraries are used elsewhere. Is there a reason that fft_filter.c doesn't use the standard library?
FWIW, I modifed the code to use the standard library in fft_filter and build the program with just the standard library and everything seemed to work.
Then, I changed all the code to use just the float library. It seems to work also and at least on receive (I haven't tried transmit), it seems to sound fine. Does the program need the precision of the standard library? Does using the float library speed up the FFT process?
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73,
Mark, N8ME
Mark Erbaugh