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New app: Spectrum Painter (#988)

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* added spectrum painter app
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Bernd Herzog 2023-05-14 23:09:43 +02:00 • committed by GitHub
parent a27881ecd6
commit b4da86d491
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24 changed files with 1457 additions and 21 deletions
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42
firmware/common/dsp_fft.hpp
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@ -33,6 +33,7 @@
#include "complex.hpp"
#include "hal.h"
#include "utility.hpp"
#include "sine_table_int8.hpp"
namespace std {
/* https://github.com/AE9RB/fftbench/blob/master/cxlr.hpp
@ -135,4 +136,45 @@ void fft_c_preswapped(std::array<T, N>& data, const size_t from, const size_t to
}
}
/*
ifft(v,N):
[0] If N==1 then return.
[1] For k = 0 to N/2-1, let ve[k] = v[2*k]
[2] Compute ifft(ve, N/2);
[3] For k = 0 to N/2-1, let vo[k] = v[2*k+1]
[4] Compute ifft(vo, N/2);
[5] For m = 0 to N/2-1, do [6] through [9]
[6] Let w.real() = cos(2*PI*m/N)
[7] Let w.imag() = sin(2*PI*m/N)
[8] Let v[m] = ve[m] + w*vo[m]
[9] Let v[m+N/2] = ve[m] - w*vo[m]
*/
template<typename T>
void ifft( T *v, int n, T *tmp )
{
if(n>1) {
int k,m;
T z, w, *vo, *ve;
ve = tmp; vo = tmp+n/2;
for(k=0; k<n/2; k++) {
ve[k] = v[2*k];
vo[k] = v[2*k+1];
}
ifft( ve, n/2, v ); /* FFT on even-indexed elements of v[] */
ifft( vo, n/2, v ); /* FFT on odd-indexed elements of v[] */
for(m=0; m<n/2; m++) {
w.real(sine_table_i8[((int)(m/(double)n * 0x100 + 0x40)) & 0xFF]);
w.imag(sine_table_i8[((int)(m/(double)n * 0x100)) & 0xFF]);
z.real((w.real()*vo[m].real() - w.imag()*vo[m].imag())/127); /* Re(w*vo[m]) */
z.imag((w.real()*vo[m].imag() + w.imag()*vo[m].real())/127); /* Im(w*vo[m]) */
v[ m ].real(ve[m].real() + z.real());
v[ m ].imag(ve[m].imag() + z.imag());
v[m+n/2].real(ve[m].real() - z.real());
v[m+n/2].imag(ve[m].imag() - z.imag());
}
}
return;
}
#endif/*__DSP_FFT_H__*/