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FIX: detect noise signal by measuring amplitude of signal.

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iceman1001 2017-10-30 19:18:30 +01:00
commit db56ca11a3
4 changed files with 44 additions and 23 deletions
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36
common/lfdemod.c
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@ -65,8 +65,9 @@ void dummy(char *fmt, ...){}
uint32_t compute_mean_uint(uint8_t *in, size_t N) {
uint32_t mean = 0;
for (size_t i = 0; i < N; i++)
mean += in[i];
return (uint32_t)mean/N;
mean += in[i];
return mean / N;
}
// Function to compute mean for a series
// rounded to integer..
@ -74,22 +75,33 @@ int32_t compute_mean_int(int *in, size_t N) {
int32_t mean = 0;
for (size_t i = 0; i < N; i++)
mean += in[i];
return (int32_t)mean/N;
return mean / (int)N;
}
//test samples are not just noise
// By measuring mean and look at amplitude of signal from HIGH / LOW,
// we can detect noise
bool justNoise(uint8_t *bits, size_t size) {
// if we take the mean on the sample set and see if its
// below the threshold, it will be a better indicator
uint32_t mean = compute_mean_uint(bits, size);
uint8_t counter = 0;
for ( size_t i = 0; i < size && counter < 10; i++) {
if ( bits[i] > mean ) counter++;
}
if (g_debugMode == 2) prnt("DEBUG: (justNoise) mean %u | %i | counter %u", mean, FSK_PSK_THRESHOLD, counter);
return counter < 10;
//might not be high enough for noisy environments
#define NOICE_AMPLITUDE_THRESHOLD 10;
uint32_t sum = 0, mean = 0, high = 0, low = 255;
for ( size_t i = 0; i < size; i++) {
if ( bits[i] < low ) low = bits[i];
if ( bits[i] > high ) high = bits[i];
sum += bits[i];
}
mean = sum / size;
// measure amplitude of signal
bool isnoise = (high - mean) < NOICE_AMPLITUDE_THRESHOLD;
if (g_debugMode == 2)
prnt("DEBUG: (justNoise) mean %u | hi %u | low %u | IS NOISE %c", mean, high, low, isnoise?'Y':'N');
return isnoise;
/*
// loop until a sample is larger than threshold.
// one sample above threshold is not a good indicator.