FSK demodulator: Also report bits that have duration < 0.5

pull/1/head
Andreas Eversberg 3 years ago
parent 445af0c0a2
commit 830794bae4
  1. 13
      src/libfsk/fsk.c
  2. 1
      src/libfsk/fsk.h

@ -324,6 +324,18 @@ void fsk_demod_receive(fsk_demod_t *fsk, sample_t *sample, int length)
if (fsk->rx_bitpos < 0.5)
fsk->rx_bitpos = 0.5;
}
/* if we have a pulse before we sampled a bit after last pulse */
if (fsk->rx_change) {
/* peak level is the length of I/Q vector
* since we filter out the unwanted modulation product, the vector is only half of length */
level = sqrt(I[i] * I[i] + Q[i] * Q[i]) * 2.0;
#ifdef DEBUG_FILTER
printf("prematurely bit change (level=%.3f)\n", level / fsk->level);
#endif
/* quality is 0.0, because a prematurely level change is caused by noise and has nothing to measure. */
fsk->receive_bit(fsk->inst, fsk->rx_bit, 0.0, level);
}
fsk->rx_change = 1;
}
/* if bit counter reaches 1, we subtract 1 and sample the bit */
if (fsk->rx_bitpos >= 1.0) {
@ -344,6 +356,7 @@ void fsk_demod_receive(fsk_demod_t *fsk, sample_t *sample, int length)
/* adjust the values, because this is best we can get from fm demodulator */
fsk->receive_bit(fsk->inst, bit, quality / 0.95, level);
fsk->rx_bitpos -= 1.0;
fsk->rx_change = 0;
}
fsk->rx_bitpos += fsk->bits_per_sample;
}

@ -30,6 +30,7 @@ typedef struct fsk_demod {
int rx_bit; /* current receiving bit (-1 if not yet measured) */
double rx_bitpos; /* current receive position in bit (sampleclock) */
double rx_bitadjust; /* how much does a bit change cause the sample clock to be adjusted in phase */
int rx_change; /* set, if we have a level change before sampling the bit */
} fsk_demod_t;
int fsk_mod_init(fsk_mod_t *fsk, void *inst, int (*send_bit)(void *inst), int samplerate, double bitrate, double f0, double f1, double level, int coherent, int filter);

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