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chg;: idea of auto adjusting signal to zero mean baseline in order to compensate different antennas

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Chris 2018-09-07 23:47:42 +02:00
parent 51fdde0bbf
commit e29bb51e76
2 changed files with 23 additions and 10 deletions
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32
common/lfdemod.c
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@ -105,6 +105,21 @@ int32_t compute_mean_int(int *in, size_t N) {
return mean / (int)N;
}
void zeromean(uint8_t* data, size_t size) {
// zero mean data
int i, accum = 0;
for (i = 10; i < size; ++i)
accum += data[i];
accum /= (size - 10);
for (i = 0; i < size; ++i)
data[i] -= accum;
}
//test samples are not just noise
// By measuring mean and look at amplitude of signal from HIGH / LOW, we can detect noise
bool isNoise_int(int *bits, uint32_t size) {
@ -1841,6 +1856,8 @@ int detectAWID(uint8_t *dest, size_t *size, int *waveStartIdx) {
if (signalprop.isnoise) return -2;
zeromean(dest, *size);
// FSK2a demodulator clock 50, invert 1, fcHigh 10, fcLow 8
*size = fskdemod(dest, *size, 50, 1, 10, 8, waveStartIdx); //awid fsk2a
@ -1898,22 +1915,15 @@ int Em410xDecode(uint8_t *bits, size_t *size, size_t *start_idx, uint32_t *hi, u
return 1;
}
// loop to get raw HID waveform then FSK demodulate the TAG ID from it
int HIDdemodFSK(uint8_t *dest, size_t *size, uint32_t *hi2, uint32_t *hi, uint32_t *lo, int *waveStartIdx) {
//make sure buffer has data
if (*size < 96*50) return -1;
if (signalprop.isnoise) return -2;
// zero mean data
int i, accum = 0;
for (i = 10; i < *size; ++i)
accum += dest[i];
accum /= (*size - 10);
for (i = 0; i < *size; ++i)
dest[i] -= accum;
zeromean(dest, *size);
// FSK demodulator fsk2a so invert and fc/10/8
*size = fskdemod(dest, *size, 50, 1, 10, 8, waveStartIdx); //hid fsk2a
@ -1974,6 +1984,8 @@ int detectIOProx(uint8_t *dest, size_t *size, int *waveStartIdx) {
if (signalprop.isnoise) return -2;
zeromean(dest, *size);
// FSK demodulator RF/64, fsk2a so invert, and fc/10/8
*size = fskdemod(dest, *size, 64, 1, 10, 8, waveStartIdx); //io fsk2a

1
common/lfdemod.h
View file

@ -34,6 +34,7 @@ extern uint32_t compute_mean_uint(uint8_t *in, size_t N);
extern int32_t compute_mean_int(int *in, size_t N);
bool isNoise_int(int *bits, uint32_t size);
bool isNoise(uint8_t *bits, uint32_t size);
extern void zeromean(uint8_t* data, size_t size);
// buffer is unsigned on DEVIE
#ifdef ON_DEVICE