diff options
Diffstat (limited to 'src/nmt/frame.c')
| -rw-r--r-- | src/nmt/frame.c | 176 |
1 files changed, 24 insertions, 152 deletions
diff --git a/src/nmt/frame.c b/src/nmt/frame.c index bde6e8d..8cad3ca 100644 --- a/src/nmt/frame.c +++ b/src/nmt/frame.c @@ -27,6 +27,7 @@ #include "../common/timer.h" #include "nmt.h" #include "frame.h" +#include "hagelbarger.h" uint64_t nmt_encode_channel(int channel, int power) { @@ -969,161 +970,25 @@ static void assemble_frame(frame_t *frame, uint8_t *digits, int debug) } } -/* encode digits of a frame to 166 bits */ -static void encode_digits(const uint8_t *digits, char *bits) -{ - uint8_t x[64]; - int i; - uint8_t digit; - - /* copy bit sync and frame sync */ - memcpy(bits, "10101010101010111100010010", 26); - bits += 26; - - for (i = 0; i < 16; i++) { - digit = *digits++; - x[(i << 2) + 0] = (digit >> 3) & 1; - x[(i << 2) + 1] = (digit >> 2) & 1; - x[(i << 2) + 2] = (digit >> 1) & 1; - x[(i << 2) + 3] = digit & 1; - } - - /* parity check bits */ - for (i = 0; i < 3; i++) - bits[(i << 1)] = '1' - x[i]; - for (i = 3; i < 64; i++) - bits[(i << 1)] = '1' - (x[i] ^ x[i - 3]); - for (i = 64; i < 67; i++) - bits[(i << 1)] = '1' - x[i - 3]; - for (i = 67; i < 70; i++) - bits[(i << 1)] = '1'; - - /* information bits */ - for (i = 0; i < 6; i++) - bits[(i << 1) + 1] = '0'; - for (i = 6; i < 70; i++) - 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) -{ - uint8_t x[64]; - int i, short_frame = 0; - - /* information bits */ - for (i = 0; i < 6; i++) { - 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'; - - /* create digits */ - for (i = 0; i < 16; i++) { - digits[i] = ((x[(i << 2) + 0] & 1) << 3) - | ((x[(i << 2) + 1] & 1) << 2) - | ((x[(i << 2) + 2] & 1) << 1) - | (x[(i << 2) + 3] & 1); - } - - /* check for short frame */ - if (callack && (digits[3] == 1 || digits[3] == 15)) { - digits[13] = 0; - 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]) { -#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 - * be omitted for short frame. It would make more sense - * to stop after Y(116), so only the last three digits - * are omitted and not the last bit of digit13 also. - * Tests have showed that it we receive correctly up to - * Y(116), but we ignore an error, if only up to Y(114) - * is received. - */ - if (short_frame && i == 51) { - PDEBUG(DFRAME, DEBUG_DEBUG, "Frame bad after bit Y(114), ignoring.\n"); - 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]) { -#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') { -#ifdef DEBUG_DECODE - PDEBUG(DFRAME, DEBUG_DEBUG, "Frame bad at parity bit #%d.\n", i); -#endif - return -1; - } - } - - return 0; -} - /* encode frame to bits * debug can be turned on or off */ const char *encode_frame(frame_t *frame, int debug) { - uint8_t digits[16]; + uint8_t digits[16], message[9], code[18]; static char bits[166]; + int i; assemble_frame(frame, digits, debug); - encode_digits(digits, bits); + + /* hagelbarger code */ + message[8] = 0x00; + for (i = 0; i < 8; i++) + message[i] = (digits[i * 2] << 4) | digits[i * 2 + 1]; + hagelbarger_encode(message, code, 72); + memcpy(bits, "10101010101010111100010010", 26); + for (i = 0; i < 140; i++) + bits[i + 26] = ((code[i / 8] >> (7 - (i & 7))) & 1) + '0'; return bits; } @@ -1131,12 +996,19 @@ const char *encode_frame(frame_t *frame, int debug) /* decode bits to frame */ int decode_frame(frame_t *frame, const char *bits, enum nmt_direction direction, int callack) { - uint8_t digits[16]; - int rc; + uint8_t digits[16], message[8], code[19]; + int i; + + /* hagelbarger code */ + memset(code, 0x00, sizeof(code)); + for (i = 0; i < 140; i++) + code[i / 8] |= (bits[i] & 1) << (7 - (i & 7)); + hagelbarger_decode(code, message, 64); + for (i = 0; i < 8; i++) { + digits[i * 2] = message[i] >> 4; + digits[i * 2 + 1] = message[i] & 0x0f; + } - rc = decode_digits(digits, bits, callack); - if (rc < 0) - return rc; disassemble_frame(frame, digits, direction, callack); return 0; |