495 lines
13 KiB
C
495 lines
13 KiB
C
/* POCSAG framing
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*
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* (C) 2021 by Andreas Eversberg <jolly@eversberg.eu>
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* All Rights Reserved
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <stdio.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include <string.h>
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#include <errno.h>
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#include "../libsample/sample.h"
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#include "../libdebug/debug.h"
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#include "pocsag.h"
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#include "frame.h"
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#define CHAN pocsag->sender.kanal
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#define PREAMBLE_COUNT 18
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#define CODEWORD_PREAMBLE 0xaaaaaaaa
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#define CODEWORD_SYNC 0x7cd215d8
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#define CODEWORD_IDLE 0x7a89c197
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#define IDLE_BATCHES 2
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static const char numeric[16] = "0123456789RU -][";
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static const char hex[16] = "0123456789abcdef";
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static const char *ctrlchar[32] = {
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"<NUL>",
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"<SOH>",
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"<STX>",
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"<ETX>",
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"<EOT>",
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"<ENQ>",
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"<ACK>",
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"<BEL>",
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"<BS>",
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"<HT>",
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"<LF>",
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"<VT>",
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"<FF>",
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"<CR>",
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"<SO>",
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"<SI>",
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"<DLE>",
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"<DC1>",
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"<DC2",
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"<DC3>",
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"<DC4>",
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"<NAK>",
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"<SYN>",
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"<ETB>",
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"<CAN>",
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"<EM>",
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"<SUB>",
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"<ESC>",
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"<FS>",
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"<GS>",
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"<RS>",
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"<US>",
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};
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static uint32_t pocsag_crc(uint32_t word)
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{
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uint32_t denominator = 0x76900000;
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int i;
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word <<= 10;
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for (i = 0; i < 21; i++) {
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if ((word >> (30 - i)) & 1)
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word ^= denominator;
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denominator >>= 1;
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}
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return word & 0x3ff;
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}
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static uint32_t pocsag_parity(uint32_t word)
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{
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word ^= word >> 16;
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word ^= word >> 8;
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word ^= word >> 4;
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word ^= word >> 2;
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word ^= word >> 1;
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return word & 1;
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}
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static int debug_word(uint32_t word, int slot)
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{
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if (pocsag_crc(word >> 11) != ((word >> 1) & 0x3ff)) {
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PDEBUG(DPOCSAG, DEBUG_NOTICE, "CRC error in codeword 0x%08x.\n", word);
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return -EINVAL;
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}
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if (pocsag_parity(word)) {
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PDEBUG(DPOCSAG, DEBUG_NOTICE, "Parity error in codeword 0x%08x.\n", word);
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return -EINVAL;
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}
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if (word == CODEWORD_SYNC) {
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PDEBUG(DPOCSAG, DEBUG_DEBUG, "-> valid sync word\n");
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return 0;
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}
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if (word == CODEWORD_IDLE) {
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PDEBUG(DPOCSAG, DEBUG_DEBUG, "-> valid idle word\n");
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return 0;
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}
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if (!(word & 0x80000000)) {
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PDEBUG(DPOCSAG, DEBUG_DEBUG, "-> valid address word: RIC = '%d', function = '%d' (%s)\n", ((word >> 10) & 0x1ffff8) + slot, (word >> 11) & 0x3, pocsag_function_name[(word >> 11) & 0x3]);
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} else {
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PDEBUG(DPOCSAG, DEBUG_DEBUG, "-> valid message word: message = '0x%05x'\n", (word >> 11) & 0xfffff);
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}
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return 0;
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}
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static uint32_t encode_address(pocsag_msg_t *msg)
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{
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uint32_t word;
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/* compose message */
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word = 0x0;
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/* RIC */
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word = (word << 18) | (msg->ric >> 3);
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word = (word << 2) | msg->function;
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word = (word << 10) | pocsag_crc(word);
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word = (word << 1) | pocsag_parity(word);
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return word;
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}
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static void decode_address(uint32_t word, uint8_t slot, uint32_t *ric, enum pocsag_function *function)
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{
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*ric = ((word >> 10) & 0x1ffff8) + slot;
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*function = (word >> 11) & 0x3;
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}
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static uint32_t encode_numeric(pocsag_msg_t *msg)
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{
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uint8_t digit[5] = { 0xc, 0xc, 0xc, 0xc, 0xc };
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int index, i;
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uint32_t word;
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/* get characters from string */
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index = 0;
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while (msg->data_index < msg->data_length) {
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for (i = 0; i < 16; i++) {
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if (numeric[i] == msg->data[msg->data_index])
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break;
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}
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msg->data_index++;
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if (i < 16)
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digit[index++] = i;
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if (index == 5)
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break;
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}
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/* compose message */
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word = 0x1;
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for (i = 0; i < 5; i++) {
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word = (word << 1) | (digit[i] & 0x1);
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word = (word << 1) | ((digit[i] >> 1) & 0x1);
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word = (word << 1) | ((digit[i] >> 2) & 0x1);
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word = (word << 1) | ((digit[i] >> 3) & 0x1);
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}
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word = (word << 10) | pocsag_crc(word);
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word = (word << 1) | pocsag_parity(word);
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return word;
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}
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static void decode_numeric(pocsag_t *pocsag, uint32_t word)
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{
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uint8_t digit;
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int i;
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for (i = 0; i < 5; i++) {
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if (pocsag->rx_msg_data_length == sizeof(pocsag->rx_msg_data))
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return;
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digit = (word >> (27 - i * 4)) & 0x1;
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digit = (digit << 1) | ((word >> (28 - i * 4)) & 0x1);
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digit = (digit << 1) | ((word >> (29 - i * 4)) & 0x1);
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digit = (digit << 1) | ((word >> (30 - i * 4)) & 0x1);
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pocsag->rx_msg_data[pocsag->rx_msg_data_length++] = numeric[digit];
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}
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}
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static uint32_t encode_alpha(pocsag_msg_t *msg)
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{
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int bits;
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uint32_t word;
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/* compose message */
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word = 0x1;
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bits = 0;
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/* get character from string */
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while (msg->data_index < msg->data_length) {
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if ((msg->data[msg->data_index] & 0x80)) {
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msg->data_index++;
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continue;
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}
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while (42) {
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word = (word << 1) | ((msg->data[msg->data_index] >> msg->bit_index) & 1);
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bits++;
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if (++msg->bit_index == 7) {
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msg->bit_index = 0;
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msg->data_index++;
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break;
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}
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if (bits == 20)
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break;
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}
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if (bits == 20)
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break;
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}
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/* fill remaining digit space with 0x04 (EOT) */
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while (bits <= 13) {
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word = (word << 7) | 0x10;
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bits += 7;
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}
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/* fill remaining bits with '0's */
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if (bits < 20)
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word <<= 20 - bits;
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word = (word << 10) | pocsag_crc(word);
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word = (word << 1) | pocsag_parity(word);
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return word;
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}
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static void decode_alpha(pocsag_t *pocsag, uint32_t word)
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{
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int i;
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for (i = 0; i < 20; i++) {
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if (pocsag->rx_msg_data_length == sizeof(pocsag->rx_msg_data))
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return;
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if (!pocsag->rx_msg_bit_index)
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pocsag->rx_msg_data[pocsag->rx_msg_data_length] = 0x00;
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pocsag->rx_msg_data[pocsag->rx_msg_data_length] >>= 1;
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pocsag->rx_msg_data[pocsag->rx_msg_data_length] |= ((word >> (30 - i)) & 0x1) << 6;
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if (++pocsag->rx_msg_bit_index == 7) {
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pocsag->rx_msg_bit_index = 0;
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pocsag->rx_msg_data_length++;
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}
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}
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}
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static void decode_hex(pocsag_t *pocsag, uint32_t word)
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{
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uint8_t digit;
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int i;
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for (i = 0; i < 5; i++) {
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if (pocsag->rx_msg_data_length == sizeof(pocsag->rx_msg_data))
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return;
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digit = (word >> (27 - i * 4)) & 0x1;
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digit = (digit << 1) | ((word >> (28 - i * 4)) & 0x1);
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digit = (digit << 1) | ((word >> (29 - i * 4)) & 0x1);
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digit = (digit << 1) | ((word >> (30 - i * 4)) & 0x1);
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pocsag->rx_msg_data[pocsag->rx_msg_data_length++] = hex[digit];
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}
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}
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/* get codeword from scheduler */
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int64_t get_codeword(pocsag_t *pocsag)
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{
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pocsag_msg_t *msg;
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uint32_t word = 0; // make GCC happy
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uint8_t slot = (pocsag->word_count - 1) >> 1;
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uint8_t subslot = (pocsag->word_count - 1) & 1;
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/* no codeword, if not transmitting */
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if (!pocsag->tx)
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return -1;
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/* transmitter state */
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switch (pocsag->state) {
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case POCSAG_IDLE:
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return -1;
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case POCSAG_PREAMBLE:
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if (!pocsag->word_count)
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PDEBUG_CHAN(DPOCSAG, DEBUG_INFO, "Sending preamble.\n");
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/* transmit preamble */
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PDEBUG_CHAN(DPOCSAG, DEBUG_DEBUG, "Sending 32 bits of preamble pattern 0x%08x.\n", CODEWORD_PREAMBLE);
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if (++pocsag->word_count == PREAMBLE_COUNT) {
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pocsag_new_state(pocsag, POCSAG_MESSAGE);
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pocsag->word_count = 0;
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pocsag->idle_count = 0;
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}
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word = CODEWORD_PREAMBLE;
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break;
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case POCSAG_MESSAGE:
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if (!pocsag->word_count)
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PDEBUG_CHAN(DPOCSAG, DEBUG_INFO, "Sending batch.\n");
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/* send sync */
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if (pocsag->word_count == 0) {
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PDEBUG_CHAN(DPOCSAG, DEBUG_DEBUG, "Sending 32 bits of sync pattern 0x%08x.\n", CODEWORD_SYNC);
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/* count codewords */
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++pocsag->word_count;
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word = CODEWORD_SYNC;
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break;
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}
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/* send message data, if there is an ongoing message */
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if ((msg = pocsag->current_msg)) {
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/* reset idle counter */
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pocsag->idle_count = 0;
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/* encode data */
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switch (msg->function) {
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case POCSAG_FUNCTION_NUMERIC:
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word = encode_numeric(msg);
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break;
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case POCSAG_FUNCTION_ALPHA:
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word = encode_alpha(msg);
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break;
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default:
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word = CODEWORD_IDLE; /* should never happen */
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}
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/* if message is complete, reset index. if message is not to be repeated, remove message */
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if (msg->data_index == msg->data_length) {
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pocsag->current_msg = NULL;
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msg->data_index = 0;
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if (msg->repeat || pocsag->sender.loopback)
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msg->repeat--;
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else
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pocsag_msg_destroy(msg);
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}
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/* prevent 'use-after-free' from this point on */
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msg = NULL;
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PDEBUG_CHAN(DPOCSAG, DEBUG_DEBUG, "Sending 32 bits of message codeword 0x%08x (frame %d.%d).\n", word, slot, subslot);
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/* count codewords */
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if (++pocsag->word_count == 17)
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pocsag->word_count = 0;
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break;
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}
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/* if we are about to send an address codeword, we search for a pending message */
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for (msg = pocsag->msg_list; msg; msg = msg->next) {
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/* if a message matches the right time slot */
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if ((msg->ric & 7) == slot)
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break;
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}
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if (msg) {
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PDEBUG_CHAN(DPOCSAG, DEBUG_INFO, "Sending message to RIC '%d' / function '%d' (%s)\n", msg->ric, msg->function, pocsag_function_name[msg->function]);
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/* reset idle counter */
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pocsag->idle_count = 0;
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/* encode address */
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word = encode_address(msg);
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/* link message, if there is data to be sent */
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if ((msg->function == POCSAG_FUNCTION_NUMERIC || msg->function == POCSAG_FUNCTION_ALPHA) && msg->data_length) {
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char text[msg->data_length + 1];
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memcpy(text, msg->data, msg->data_length);
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text[msg->data_length] = '\0';
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PDEBUG_CHAN(DPOCSAG, DEBUG_INFO, " -> Message text is \"%s\".\n", text);
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pocsag->current_msg = msg;
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msg->data_index = 0;
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msg->bit_index = 0;
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} else {
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/* if message is not to be repeated, remove message */
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if (msg->repeat || pocsag->sender.loopback)
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msg->repeat--;
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else
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pocsag_msg_destroy(msg);
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/* prevent 'use-after-free' from this point on */
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msg = NULL;
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}
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PDEBUG_CHAN(DPOCSAG, DEBUG_DEBUG, "Sending 32 bits of address codeword 0x%08x (frame %d.%d).\n", word, slot, subslot);
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/* count codewords */
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if (++pocsag->word_count == 17)
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pocsag->word_count = 0;
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break;
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}
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/* no message, so we send idle pattern */
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PDEBUG_CHAN(DPOCSAG, DEBUG_DEBUG, "Sending 32 bits of idle pattern 0x%08x (frame %d.%d).\n", CODEWORD_IDLE, slot, subslot);
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/* count codewords */
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if (++pocsag->word_count == 17) {
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pocsag->word_count = 0;
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/* if no message has been scheduled during transmission and idle counter is reached, stop transmitter */
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if (!pocsag->msg_list && pocsag->idle_count++ == IDLE_BATCHES) {
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PDEBUG_CHAN(DPOCSAG, DEBUG_INFO, "Transmission done.\n");
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PDEBUG_CHAN(DPOCSAG, DEBUG_DEBUG, "Reached %d of idle batches, turning transmitter off.\n", IDLE_BATCHES);
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pocsag_new_state(pocsag, POCSAG_IDLE);
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}
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}
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word = CODEWORD_IDLE;
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break;
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}
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if (word != CODEWORD_PREAMBLE)
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debug_word(word, slot);
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return word;
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}
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static void done_rx_msg(pocsag_t *pocsag)
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{
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if (!pocsag->rx_msg_valid)
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return;
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pocsag->rx_msg_valid = 0;
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PDEBUG_CHAN(DPOCSAG, DEBUG_INFO, "Received message from RIC '%d' / function '%d' (%s)\n", pocsag->rx_msg_ric, pocsag->rx_msg_function, pocsag_function_name[pocsag->rx_msg_function]);
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{
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char text[pocsag->rx_msg_data_length * 5 + 1];
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int i, j;
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for (i = 0, j = 0; i < pocsag->rx_msg_data_length; i++) {
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if (pocsag->rx_msg_data[i] == 127) {
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strcpy(text + j, "<DEL>");
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j += strlen(text + j);
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} else
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if (pocsag->rx_msg_data[i] < 32) {
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strcpy(text + j, ctrlchar[(int)pocsag->rx_msg_data[i]]);
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j += strlen(text + j);
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} else
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text[j++] = pocsag->rx_msg_data[i];
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}
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text[j] = '\0';
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PDEBUG_CHAN(DPOCSAG, DEBUG_INFO, " -> Message text is \"%s\".\n", text);
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pocsag_msg_receive(pocsag->language, pocsag->sender.kanal, pocsag->rx_msg_ric, pocsag->rx_msg_function, text);
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}
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}
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void put_codeword(pocsag_t *pocsag, uint32_t word, int8_t slot, int8_t subslot)
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{
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int rc;
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if (slot < 0 && word == CODEWORD_SYNC) {
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PDEBUG_CHAN(DPOCSAG, DEBUG_DEBUG, "Received 32 bits of sync pattern 0x%08x.\n", CODEWORD_SYNC);
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return;
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}
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if (word == CODEWORD_IDLE) {
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PDEBUG_CHAN(DPOCSAG, DEBUG_DEBUG, "Received 32 bits of idle pattern 0x%08x.\n", CODEWORD_IDLE);
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} else
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if (!(word & 0x80000000))
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PDEBUG_CHAN(DPOCSAG, DEBUG_DEBUG, "Received 32 bits of address codeword 0x%08x (frame %d.%d).\n", word, slot, subslot);
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else
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PDEBUG_CHAN(DPOCSAG, DEBUG_DEBUG, "Received 32 bits of message codeword 0x%08x (frame %d.%d).\n", word, slot, subslot);
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rc = debug_word(word, slot);
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if (rc < 0) {
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done_rx_msg(pocsag);
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return;
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}
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if (word == CODEWORD_IDLE) {
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done_rx_msg(pocsag);
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return;
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}
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if (!(word & 0x80000000)) {
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done_rx_msg(pocsag);
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pocsag->rx_msg_valid = 1;
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decode_address(word, slot, &pocsag->rx_msg_ric, &pocsag->rx_msg_function);
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pocsag->rx_msg_data_length = 0;
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pocsag->rx_msg_bit_index = 0;
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} else {
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if (!pocsag->rx_msg_valid)
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return;
|
|
switch (pocsag->rx_msg_function) {
|
|
case POCSAG_FUNCTION_NUMERIC:
|
|
decode_numeric(pocsag, word);
|
|
break;
|
|
case POCSAG_FUNCTION_ALPHA:
|
|
decode_alpha(pocsag, word);
|
|
break;
|
|
default:
|
|
decode_hex(pocsag, word);
|
|
;
|
|
}
|
|
}
|
|
}
|
|
|