Rename, add data processing thread and internal state

1 files changed, 137 insertions, 0 deletions

diff --git a/gascop.c b/gascop.c
new file mode 100644
index 0000000..b50929a
--- /dev/null
+++ b/gascop.c
@@ -0,0 +1,137 @@
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <pthread.h>
+#include <stdint.h>
+#include <errno.h>
+#include <unistd.h>
+#include <math.h>
+#include <sys/time.h>
+#include <signal.h>
+#include <fcntl.h>
+#include <ctype.h>
+#include "rtl-sdr.h"
+
+/* POCSAG parameters */
+#define POCSAG_ID "POCSAG"
+#define POCSAG_SYM_RATE 1200
+#define POCSAG_FM_DEV 4500
+#define POCSAG_SPS 8
+#define POCSAG_STD_SYNC 0x7cd215d8
+#define POCSAG_STD_IDLE 0x7a89c197
+#define POCSAG_WORDSIZE 32
+#define POCSAG_SOFTTHRESHOLD 2
+#define POCSAG_MAXWORD 16
+
+#define POCSAG_ASYNC_BUF_NUMBER 12
+#define POCSAG_DATA_LEN (16*16384) /* 256K */
+#define POCSAG_AUTO_GAIN -100 /* Use automatic gain. */
+#define POCSAG_MAX_GAIN 999999 /* Use max available gain. */
+
+/* BCH parameters */
+#define POCSAG_BCH_POLY 0x769
+#define POCSAG_BCH_N 31
+#define POCSAG_BCH_K 21
+
+/* POCASG states */
+#define POCSAG_SEARCH_PREAMBLE_START 0
+#define POCSAG_SEARCH_PREAMBLE_END 1
+#define POCSAG_SYNC 2
+#define POCSAG_SEARCH_SYNC 3
+#define POCSAG_SYNCHED 4
+
+#define IGNORE(V) ((void) V)
+
+struct {
+    pthread_t reader_thread;
+    pthread_mutex_t data_mutex;     /* Mutex to synchronize buffer access. */
+    pthread_cond_t data_cond;       /* Conditional variable associated. */
+    unsigned char *data;            /* Raw IQ samples buffer */
+    uint16_t *magnitude;            /* Magnitude vector */
+    uint32_t data_len;              /* Buffer length. */
+    int data_ready;                 /* Data ready to be processed. */
+    uint16_t *maglut;               /* I/Q -> Magnitude lookup table. */
+    int exit; 
+
+    /* rtlsdr */
+    int dev_index;
+    int gain;
+    int enable_agc;
+    rtlsdr_dev_t *dev;
+    int freq;
+} Gascop;
+
+int hammingWeight(uint32_t n) {
+    unsigned int c;
+    for (c = 0; n; c++)
+        n &= n - 1;
+    return c;
+}
+
+int evenParity(int n) {
+    return hammingWeight(n) & 1;
+}
+
+int bchSyndrome(int data, int poly, int n, int k) {
+    int mask = 1 << (n - 1);
+    int coeff = poly << (k - 1);
+    n = k;
+
+    int s = data >> 1;
+    while (n > 0) {
+        if (s & mask)
+            s ^= coeff;
+        n -= 1;
+        mask >>= 1;
+        coeff >>= 1;
+    }
+
+    if (evenParity(data))
+        s |= 1 << (n - k);
+
+    return s;
+}
+
+int bchFix(int data, int poly, int n, int k) {
+    int i, j;
+    for (i=0; i<32; i++) {
+        int t = data ^ (1 << i);
+        if (!bchSyndrome(t, poly, n, k))
+            return t;
+    }
+    for (i=0; i<32; i++) {
+        for (j=i+1; j<32; j++) {
+            int t = data ^ ((1 << i) | (1 << j));
+            if (!bchSyndrome(t, poly, n, k))
+                return t;
+        }
+    }
+    return data;
+}
+
+void rtlsdrCallback(unsigned char *buf, uint32_t len, void *ctx) {
+    IGNORE(ctx);
+
+    pthread_mutex_lock(&Gascop.data_mutex);
+    if (len > Gascop.data_len) len = Gascop.data_len;
+    memcpy(Gascop.data, buf, len);
+    Gascop.data_ready = 1;
+    pthread_cond_signal(&Gascop.data_cond);
+    pthread_mutex_unlock(&Gascop.data_mutex);
+}
+
+void *readerThreadEntryPoint(void *arg) {
+    IGNORE(arg);
+
+    rtlsdr_read_async(Gascop.dev, rtlsdrCallback, NULL,
+        POCSAG_ASYNC_BUF_NUMBER, Gascop.data_len);
+    return NULL;
+}
+
+int main(int argc, char **argv) {
+    IGNORE(argc);
+    IGNORE(argv);
+
+    printf("Dumpocsag v0.1\n");
+    exit(0);
+}