diff options
| -rw-r--r-- | src/nmt/frame.c | 49 |
1 files changed, 45 insertions, 4 deletions
diff --git a/src/nmt/frame.c b/src/nmt/frame.c index 1a07970..d70e785 100644 --- a/src/nmt/frame.c +++ b/src/nmt/frame.c @@ -879,6 +879,9 @@ static void encode_digits(const uint8_t *digits, char *bits) bits[(i << 1) + 1] = x[i - 6] + '0'; } +/* debug parity check */ +//#define DEBUG_DECODE + /* decode digits from 140 bits (not including sync) */ // FIXME: do real convolutional decoding static int decode_digits(uint8_t *digits, const char *bits, int callack) @@ -888,8 +891,12 @@ static int decode_digits(uint8_t *digits, const char *bits, int callack) /* information bits */ for (i = 0; i < 6; i++) { - if (bits[(i << 1) + 1] != '0') + if (bits[(i << 1) + 1] != '0') { +#ifdef DEBUG_DECODE + PDEBUG(DFRAME, DEBUG_DEBUG, "Frame bad at information bit #%d.\n", i); +#endif return -1; + } } for (i = 6; i < 70; i++) x[i - 6] = bits[(i << 1) + 1] - '0'; @@ -908,13 +915,22 @@ static int decode_digits(uint8_t *digits, const char *bits, int callack) digits[14] = 0; digits[15] = 0; short_frame = 1; +#ifdef DEBUG_DECODE + PDEBUG(DFRAME, DEBUG_DEBUG, "Received shortened frame\n"); +#endif } /* parity check bits */ for (i = 0; i < 3; i++) { - if (bits[(i << 1)] != '1' - x[i]) + if (bits[(i << 1)] != '1' - x[i]) { +#ifdef DEBUG_DECODE + PDEBUG(DFRAME, DEBUG_DEBUG, "Frame bad at parity bit #%d.\n", i); +#endif return -1; + } } +#if 0 +#warning this check does not work, since we get error even at bit 50 for (i = 3; i < ((short_frame) ? 52 : 64); i++) { if (bits[(i << 1)] != '1' - (x[i] ^ x[i - 3])) { /* According to NMT Doc 450-3, bits after Y(114) shall @@ -930,18 +946,43 @@ static int decode_digits(uint8_t *digits, const char *bits, int callack) digits[13] = 0; break; } +#ifdef DEBUG_DECODE + PDEBUG(DFRAME, DEBUG_DEBUG, "Frame bad at parity bit #%d.\n", i); +#endif + return -1; + } + } +#endif + /* Tests showed corrupt frame at parity #50 (i == 50) + * We just ignore whatever we receive after 48 bits of checksum. + * This is not the correct approach, but in case of a corrupt + * frame 10.a, we would drop it, if it failes later checks. + */ + for (i = 3; i < ((short_frame) ? 48 : 64); i++) { + if (bits[(i << 1)] != '1' - (x[i] ^ x[i - 3])) { +#ifdef DEBUG_DECODE + PDEBUG(DFRAME, DEBUG_DEBUG, "Frame bad at parity bit #%d.\n", i); +#endif return -1; } } if (short_frame) return 0; for (i = 64; i < 67; i++) { - if (bits[(i << 1)] != '1' - x[i - 3]) + if (bits[(i << 1)] != '1' - x[i - 3]) { +#ifdef DEBUG_DECODE + PDEBUG(DFRAME, DEBUG_DEBUG, "Frame bad at parity bit #%d.\n", i); +#endif return -1; + } } for (i = 67; i < 70; i++) { - if (bits[(i << 1)] != '1') + if (bits[(i << 1)] != '1') { +#ifdef DEBUG_DECODE + PDEBUG(DFRAME, DEBUG_DEBUG, "Frame bad at parity bit #%d.\n", i); +#endif return -1; + } } return 0; |