diff options
author | Andreas Eversberg <jolly@eversberg.eu> | 2017-07-24 19:18:01 +0200 |
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committer | Andreas Eversberg <jolly@eversberg.eu> | 2017-08-08 12:53:48 +0200 |
commit | 0cbd9657d20fb300d4fc2039ec137988eb40d21a (patch) | |
tree | 6fc80af8fb3f701eca4a4b98b8b851eaa599ac20 /src/nmt | |
parent | 6c6402571758340c640bd2350599ff6a9e5ffeb6 (diff) |
Move Hagelbarger error correction code from NMT to common code
It will be used by Radiocom 2000 also.
Some minor fixes and improvements apply.
Diffstat (limited to 'src/nmt')
-rw-r--r-- | src/nmt/Makefile.am | 1 | ||||
-rw-r--r-- | src/nmt/frame.c | 4 | ||||
-rw-r--r-- | src/nmt/hagelbarger.c | 87 | ||||
-rw-r--r-- | src/nmt/hagelbarger.h | 4 |
4 files changed, 2 insertions, 94 deletions
diff --git a/src/nmt/Makefile.am b/src/nmt/Makefile.am index 1f738b9..91d5cff 100644 --- a/src/nmt/Makefile.am +++ b/src/nmt/Makefile.am @@ -8,7 +8,6 @@ nmt_SOURCES = \ countries.c \ transaction.c \ dsp.c \ - hagelbarger.c \ frame.c \ dms.c \ sms.c \ diff --git a/src/nmt/frame.c b/src/nmt/frame.c index b64a37c..fc9ae47 100644 --- a/src/nmt/frame.c +++ b/src/nmt/frame.c @@ -25,9 +25,9 @@ #include "../common/sample.h" #include "../common/debug.h" #include "../common/timer.h" +#include "../common/hagelbarger.h" #include "nmt.h" #include "frame.h" -#include "hagelbarger.h" uint64_t nmt_encode_channel(int nmt_system, int channel, int power) { @@ -1146,7 +1146,7 @@ const char *encode_frame(int nmt_system, frame_t *frame, int debug) message[8] = 0x00; for (i = 0; i < 8; i++) message[i] = (digits[i * 2] << 4) | digits[i * 2 + 1]; - hagelbarger_encode(message, code, 72); + hagelbarger_encode(message, code, 70); memcpy(bits, "10101010101010111100010010", 26); for (i = 0; i < 140; i++) bits[i + 26] = ((code[i / 8] >> (7 - (i & 7))) & 1) + '0'; diff --git a/src/nmt/hagelbarger.c b/src/nmt/hagelbarger.c deleted file mode 100644 index f6ac2cd..0000000 --- a/src/nmt/hagelbarger.c +++ /dev/null @@ -1,87 +0,0 @@ -/* Hagelbarger (6,19) code - * - * A burst up to 6 encoded bits may be corrupt, to correct them. - * After corrupt bits, a minimum of 19 bits must be correct to correct - * another burst of corrupted bits. - * - * There is no parity check, so it is required to check all information - * elements of each message. Messages that contain signals or digits are - * protected by repeating the digits in the information element. - * - * (C) 2017 by Andreas Eversberg <jolly@eversberg.eu> - * All Rights Reserved - * - * This program is free software: you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation, either version 3 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program. If not, see <http://www.gnu.org/licenses/>. - */ - -#include "stdint.h" - -/* To encode NMT message: (MSB first) - * Use input with 9 bytes, the last byte must be 0x00. - * Use output with 18 bytes, ignore the last four (lower) bits of last byte. - * Use length of 72. - */ -void hagelbarger_encode(const uint8_t *input, uint8_t *output, int length) -{ - uint8_t reg = 0x00, data, check; - int i; - - for (i = 0; i < length; i++) { - /* get data from input (MSB first) */ - data = (input[i / 8] >> (7 - (i & 7))) & 1; - /* push data into shift register (LSB first) */ - reg = (reg << 1) | data; - /* get data bit from register */ - data = (reg >> 6) & 1; - /* calc check bit from register */ - check = (reg + (reg >> 3) + 1) & 1; - /* put check bit and data bit to output (MSB first) */ - output[i / 4] = (output[i / 4] << 2) | (check << 1) | data; - } -} - -/* To decode NMT message: (MSB first) - * Use input with 19 bytes, the unused last 12 (lower) bits must be zero. - * Use output with 8 bytes. - * Use length of 64. - */ -void hagelbarger_decode(const uint8_t *input, uint8_t *output, int length) -{ - uint16_t reg_data = 0x00, reg_check = 0x00, data, check, r_parity, s_parity; - int i; - - length += 10; - - for (i = 0; i < length; i++) { - /* get check bit from input (MSB first) */ - check = (input[i / 4] >> (7 - (i & 3) * 2)) & 1; - /* get data bit from input (MSB first) */ - data = (input[i / 4] >> (6 - (i & 3) * 2)) & 1; - /* push check bit into shift register (LSB first) */ - reg_check = (reg_check << 1) | check; - /* push data bit into shift register (LSB first) */ - reg_data = (reg_data << 1) | data; - /* calculate parity */ - r_parity = (reg_data + (reg_data >> 3) + (reg_check >> 6) + 1) & 1; - s_parity = ((reg_data >> 3) + (reg_data >> 6) + (reg_check >> 9) + 1) & 1; - /* flip message bit, if both parity checks fail */ - /* use 4th bit that will be shifted to 5th bit next loop */ - if (r_parity && s_parity) - reg_data ^= 0x0008; - /* put message bit to output (MSB first) */ - if (i >= 10) - output[(i - 10) / 8] = (output[(i - 10) / 8] << 1) | ((reg_data >> 4) & 1); - } -} - diff --git a/src/nmt/hagelbarger.h b/src/nmt/hagelbarger.h deleted file mode 100644 index 9076afc..0000000 --- a/src/nmt/hagelbarger.h +++ /dev/null @@ -1,4 +0,0 @@ - -void hagelbarger_encode(const uint8_t *input, uint8_t *output, int length); -void hagelbarger_decode(const uint8_t *input, uint8_t *output, int length); - |