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Add #ifdef-ed code to display mode A/C signals graphically.

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This commit is contained in:
Oliver Jowett 2016-11-12 17:13:36 +00:00
parent 32231cf142
commit 5063efe064
1 changed files with 87 additions and 0 deletions
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87
demod_2400.c
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@ -21,6 +21,10 @@
#include <assert.h>
#ifdef MODEAC_DEBUG
#include <gd.h>
#endif
// 2.4MHz sampling rate version
//
// When sampling at 2.4MHz we have exactly 6 samples per 5 symbols.
@ -368,6 +372,85 @@ void demodulate2400(struct mag_buf *mag)
}
#ifdef MODEAC_DEBUG
static int yscale(unsigned signal)
{
return (int) (299 - 299.0 * signal / 65536.0);
}
static void draw_modeac(uint16_t *m, unsigned modeac, unsigned f1_clock, unsigned noise_threshold, unsigned signal_threshold, unsigned bits, unsigned noisy_bits, unsigned uncertain_bits)
{
// 25 bits at 87*60MHz
// use 1 pixel = 30MHz = 1087 pixels
gdImagePtr im = gdImageCreate(1088, 300);
int red = gdImageColorAllocate(im, 255, 0, 0);
int brightgreen = gdImageColorAllocate(im, 0, 255, 0);
int darkgreen = gdImageColorAllocate(im, 0, 180, 0);
int blue = gdImageColorAllocate(im, 0, 0, 255);
int grey = gdImageColorAllocate(im, 200, 200, 200);
int white = gdImageColorAllocate(im, 255, 255, 255);
int black = gdImageColorAllocate(im, 0, 0, 0);
gdImageFilledRectangle(im, 0, 0, 1087, 299, white);
// draw samples
for (unsigned pixel = 0; pixel < 1088; ++pixel) {
int clock_offset = (pixel - 150) * 2;
int bit = clock_offset / 87;
int sample = (f1_clock + clock_offset) / 25;
int bitoffset = clock_offset % 87;
int color;
if (sample < 0)
continue;
if (clock_offset < 0 || bit >= 20) {
color = grey;
} else if (bitoffset < 27 && (uncertain_bits & (1 << (19-bit)))) {
color = red;
} else if (bitoffset >= 27 && (noisy_bits & (1 << (19-bit)))) {
color = red;
} else if (bitoffset >= 27) {
color = grey;
} else if (bits & (1 << (19-bit))) {
color = brightgreen;
} else {
color = darkgreen;
}
gdImageLine(im, pixel, 299, pixel, yscale(m[sample]), color);
}
// draw bit boundaries
for (unsigned bit = 0; bit < 20; ++bit) {
unsigned clock = 87 * bit;
unsigned pixel0 = clock / 2 + 150;
unsigned pixel1 = (clock + 27) / 2 + 150;
gdImageLine(im, pixel0, 0, pixel0, 299, (bit == 0 || bit == 14) ? black : grey);
gdImageLine(im, pixel1, 0, pixel1, 299, (bit == 0 || bit == 14) ? black : grey);
}
// draw thresholds
gdImageLine(im, 0, yscale(noise_threshold), 1087, yscale(noise_threshold), blue);
gdImageLine(im, 0, yscale(signal_threshold), 1087, yscale(signal_threshold), blue);
// save it
static int file_counter;
char filename[PATH_MAX];
sprintf(filename, "modeac_%04X_%04d.png", modeac, ++file_counter);
fprintf(stderr, "writing %s\n", filename);
FILE *pngout = fopen(filename, "wb");
gdImagePng(im, pngout);
fclose(pngout);
gdImageDestroy(im);
}
#endif
//////////
////////// MODE A/C
@ -548,6 +631,10 @@ void demodulate2400AC(struct mag_buf *mag)
((bits & 0x00040) ? 0x0004 : 0) | // D4
((bits & 0x00004) ? 0x0080 : 0); // SPI
#ifdef MODEAC_DEBUG
draw_modeac(m, modeac, f1_clock, noise_threshold, signal_threshold, bits, noisy_bits, uncertain_bits);
#endif
// This message looks good, submit it
// compute message receive time as block-start-time + difference in the 12MHz clock