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Merge pull request #32 from cho45/timedomain

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[proposal] Time Domain Operation
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TT 2019-09-19 06:17:23 +09:00 • committed by GitHub
commit e89c9bd6a7
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5 changed files with 383 additions and 36 deletions
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92
main.c
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@ -23,6 +23,7 @@
#include "usbcfg.h"
#include "si5351.h"
#include "nanovna.h"
#include "fft.h"
#include <chprintf.h>
#include <shell.h>
@ -107,6 +108,91 @@ toggle_sweep(void)
sweep_enabled = !sweep_enabled;
}
float bessel0(float x) {
const float eps = 0.0001;
float ret = 0;
float term = 1;
float m = 0;
while (term > eps * ret) {
ret += term;
++m;
term *= (x*x) / (4*m*m);
}
return ret;
}
float kaiser_window(float k, float n, float beta) {
if (beta == 0.0) return 1.0;
float r = (2 * k) / (n - 1) - 1;
return bessel0(beta * sqrt(1 - r * r)) / bessel0(beta);
}
static
void
transform_domain(void)
{
if ((domain_mode & DOMAIN_MODE) != DOMAIN_TIME) return; // nothing to do for freq domain
// use spi_buffer as temporary buffer
// and calculate ifft for time domain
float* tmp = (float*)spi_buffer;
uint8_t window_size, offset;
switch (domain_mode & TD_FUNC) {
case TD_FUNC_BANDPASS:
offset = 0;
window_size = 101;
break;
case TD_FUNC_LOWPASS_IMPULSE:
case TD_FUNC_LOWPASS_STEP:
offset = 101;
window_size = 202;
break;
}
float beta = 0.0;
switch (domain_mode & TD_WINDOW) {
case TD_WINDOW_MINIMUM:
beta = 0.0; // this is rectangular
break;
case TD_WINDOW_NORMAL:
beta = 6.0;
break;
case TD_WINDOW_MAXIMUM:
beta = 13;
break;
}
for (int ch = 0; ch < 2; ch++) {
memcpy(tmp, measured[ch], sizeof(measured[0]));
if (beta != 0.0) {
for (int i = 0; i < 101; i++) {
float w = kaiser_window(i+offset, window_size, beta);
tmp[i*2+0] *= w;
tmp[i*2+1] *= w;
}
}
for (int i = 101; i < 128; i++) {
tmp[i*2+0] = 0.0;
tmp[i*2+1] = 0.0;
}
fft128_inverse((float(*)[2])tmp);
memcpy(measured[ch], tmp, sizeof(measured[0]));
for (int i = 0; i < 101; i++) {
measured[ch][i][0] /= 128.0;
measured[ch][i][1] /= 128.0;
}
if ( (domain_mode & TD_FUNC) == TD_FUNC_LOWPASS_STEP ) {
for (int i = 1; i < 101; i++) {
measured[ch][i][0] += measured[ch][i-1][0];
measured[ch][i][1] += measured[ch][i-1][1];
}
}
}
}
static void cmd_pause(BaseSequentialStream *chp, int argc, char *argv[])
{
(void)chp;
@ -515,6 +601,8 @@ properties_t current_props = {
{ 1, 30, 0 }, { 0, 40, 0 }, { 0, 60, 0 }, { 0, 80, 0 }
},
/* active_marker */ 0,
/* domain_mode */ 0,
/* velocity_factor */ 70,
/* checksum */ 0
};
properties_t *active_props = &current_props;
@ -599,11 +687,13 @@ void sweep(void)
redraw_requested = FALSE;
ui_process();
if (redraw_requested)
return; // return to redraw screen asap.
break; // return to redraw screen asap.
if (frequency_updated)
goto rewind;
}
transform_domain();
}
static void