mirror of
https://github.com/portapack-mayhem/mayhem-firmware.git
synced 2024-12-13 19:54:39 +00:00
438 lines
13 KiB
C++
438 lines
13 KiB
C++
/*
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* Copyright (C) 2015 Jared Boone, ShareBrained Technology, Inc.
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* Copyright (C) 2016 Furrtek
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*
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* This file is part of PortaPack.
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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 2, or (at your option)
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* 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; see the file COPYING. If not, write to
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* the Free Software Foundation, Inc., 51 Franklin Street,
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* Boston, MA 02110-1301, USA.
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*/
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#include "pocsag.hpp"
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#include "baseband_api.hpp"
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#include "portapack.hpp"
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using namespace portapack;
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#include "string_format.hpp"
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#include "utility.hpp"
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namespace pocsag {
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std::string bitrate_str(BitRate bitrate) {
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switch (bitrate) {
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case BitRate::FSK512:
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return "512bps ";
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case BitRate::FSK1200:
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return "1200bps";
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case BitRate::FSK2400:
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return "2400bps";
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case BitRate::FSK3200:
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return "3200bps";
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default:
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return "????";
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}
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}
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std::string flag_str(PacketFlag packetflag) {
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switch (packetflag) {
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case PacketFlag::NORMAL:
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return "OK";
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case PacketFlag::TIMED_OUT:
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return "TIMED OUT";
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default:
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return "";
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}
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}
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void insert_BCH(BCHCode& BCH_code, uint32_t* codeword) {
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uint32_t parity = 0;
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int data[21];
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int bit;
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int* bb;
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size_t c;
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for (c = 0; c < 21; c++) {
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bit = (((*codeword) << c) & 0x80000000U) ? 1 : 0;
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if (bit) parity++;
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data[c] = bit;
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}
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bb = BCH_code.encode(data);
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// Make sure ECC bits are cleared
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(*codeword) &= 0xFFFFF801;
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for (c = 0; c < 10; c++) {
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bit = bb[c];
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(*codeword) |= (bit << (10 - c));
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if (bit) parity++;
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}
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// Even parity
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(*codeword) |= (parity & 1);
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}
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uint32_t get_digit_code(char code) {
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if ((code >= '0') && (code <= '9')) {
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code -= '0';
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} else {
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if (code == 'S')
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code = 10;
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else if (code == 'U')
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code = 11;
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else if (code == ' ')
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code = 12;
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else if (code == '-')
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code = 13;
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else if (code == ']')
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code = 14;
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else if (code == '[')
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code = 15;
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else
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code = 12;
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}
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code = ((code & 0x0C) >> 2) | ((code & 0x03) << 2); // ----3210 -> ----1032
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code = ((code & 0x0A) >> 1) | ((code & 0x05) << 1); // ----1032 -> ----0123
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return code;
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}
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void pocsag_encode(const MessageType type, BCHCode& BCH_code, const uint32_t function, const std::string message, const uint32_t address, std::vector<uint32_t>& codewords) {
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size_t b, c, address_slot;
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size_t bit_idx, char_idx = 0;
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uint32_t codeword, digit_code;
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char ascii_char = 0;
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size_t message_size = message.size();
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// Preamble
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for (b = 0; b < (POCSAG_PREAMBLE_LENGTH / 32); b++) {
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codewords.push_back(0xAAAAAAAA);
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}
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// Address
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codeword = (address & 0x1FFFF8U) << 10;
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address_slot = (address & 7) * 2;
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// Function
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codeword |= (function << 11);
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insert_BCH(BCH_code, &codeword);
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// Address batch
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codewords.push_back(POCSAG_SYNCWORD);
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for (c = 0; c < 16; c++) {
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if (c == address_slot) {
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codewords.push_back(codeword);
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if (type != MessageType::ADDRESS_ONLY) break;
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} else
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codewords.push_back(POCSAG_IDLEWORD);
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}
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if (type == MessageType::ADDRESS_ONLY) return; // Done.
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c++;
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codeword = 0;
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bit_idx = 20 + 11;
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// Messages batch(es)
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do {
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if (c == 0) codewords.push_back(POCSAG_SYNCWORD);
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for (; c < 16; c++) {
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// Fill up 20 bits
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if (type == MessageType::ALPHANUMERIC) {
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if ((char_idx < message_size) || (ascii_char)) {
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do {
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bit_idx -= 7;
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if (char_idx < message_size)
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ascii_char = message[char_idx] & 0x7F;
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else
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ascii_char = 0; // Codeword padding
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// Bottom's up
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ascii_char = (ascii_char & 0xF0) >> 4 | (ascii_char & 0x0F) << 4; // *6543210 -> 3210*654
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ascii_char = (ascii_char & 0xCC) >> 2 | (ascii_char & 0x33) << 2; // 3210*654 -> 103254*6
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ascii_char = (ascii_char & 0xAA) >> 2 | (ascii_char & 0x55); // 103254*6 -> *0123456
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codeword |= (ascii_char << bit_idx);
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char_idx++;
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} while (bit_idx > 11);
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codeword &= 0x7FFFF800; // Trim data
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codeword |= 0x80000000; // Message type
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insert_BCH(BCH_code, &codeword);
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codewords.push_back(codeword);
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if (bit_idx != 11) {
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bit_idx = 20 + bit_idx;
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codeword = ascii_char << bit_idx;
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} else {
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bit_idx = 20 + 11;
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codeword = 0;
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}
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} else {
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codewords.push_back(POCSAG_IDLEWORD); // Batch padding
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}
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} else if (type == MessageType::NUMERIC_ONLY) {
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if (char_idx < message_size) {
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do {
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bit_idx -= 4;
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if (char_idx < message_size)
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digit_code = get_digit_code(message[char_idx]);
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else
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digit_code = 3; // Space (codeword padding)
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codeword |= (digit_code << bit_idx);
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char_idx++;
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} while (bit_idx > 11);
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codeword |= 0x80000000; // Message type
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insert_BCH(BCH_code, &codeword);
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codewords.push_back(codeword);
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bit_idx = 20 + 11;
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codeword = 0;
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} else {
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codewords.push_back(POCSAG_IDLEWORD); // Batch padding
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}
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}
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}
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c = 0;
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} while (char_idx < message_size);
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}
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// ----------------------------------------------------------------------------
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// EccContainer
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// ----------------------------------------------------------------------------
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EccContainer::EccContainer() {
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setup_ecc();
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}
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void EccContainer::setup_ecc() {
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unsigned int srr = 0x3b4;
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unsigned int i, n, j, k;
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/* calculate all information needed to implement error correction */
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// Note : this is only for 31,21 code used in pocsag & flex
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// one should probably also make use of 32nd parity bit
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for (i = 0; i <= 20; i++) {
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ecs[i] = srr;
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if ((srr & 0x01) != 0)
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srr = (srr >> 1) ^ 0x3B4;
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else
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srr = srr >> 1;
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}
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/* bch holds a syndrome look-up table telling which bits to correct */
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// first 5 bits hold location of first error; next 5 bits hold location
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// of second error; bits 12 & 13 tell how many bits are bad
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for (i = 0; i < 1024; i++) bch[i] = 0;
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/* two errors in data */
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for (n = 0; n <= 20; n++) {
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for (i = 0; i <= 20; i++) {
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j = (i << 5) + n;
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k = ecs[n] ^ ecs[i];
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bch[k] = j + 0x2000;
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}
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}
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/* one error in data */
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for (n = 0; n <= 20; n++) {
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k = ecs[n];
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j = n + (0x1f << 5);
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bch[k] = j + 0x1000;
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}
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/* one error in data and one error in ecc portion */
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for (n = 0; n <= 20; n++) {
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for (i = 0; i < 10; i++) /* ecc screwed up bit */
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{
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k = ecs[n] ^ (1 << i);
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j = n + (0x1f << 5);
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bch[k] = j + 0x2000;
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}
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}
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/* one error in ecc */
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for (n = 0; n < 10; n++) {
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k = 1 << n;
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bch[k] = 0x3ff + 0x1000;
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}
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/* two errors in ecc */
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for (n = 0; n < 10; n++) {
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for (i = 0; i < 10; i++) {
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if (i != n) {
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k = (1 << n) ^ (1 << i);
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bch[k] = 0x3ff + 0x2000;
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}
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}
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}
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}
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int EccContainer::error_correct(uint32_t& val) {
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int i, synd, errl, acc, pari, ecc, b1, b2;
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errl = 0;
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pari = 0;
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ecc = 0;
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for (i = 31; i >= 11; --i) {
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if (val & (1 << i)) {
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ecc = ecc ^ ecs[31 - i];
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pari = pari ^ 0x01;
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}
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}
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acc = 0;
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for (i = 10; i >= 1; --i) {
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acc = acc << 1;
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if (val & (1 << i)) {
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acc = acc ^ 0x01;
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}
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}
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synd = ecc ^ acc;
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errl = 0;
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if (synd != 0) /* if nonzero syndrome we have error */
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{
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if (bch[synd] != 0) /* check for correctable error */
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{
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b1 = bch[synd] & 0x1f;
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b2 = bch[synd] >> 5;
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b2 = b2 & 0x1f;
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if (b2 != 0x1f) {
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val ^= 0x01 << (31 - b2);
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ecc = ecc ^ ecs[b2];
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}
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if (b1 != 0x1f) {
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val ^= 0x01 << (31 - b1);
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ecc = ecc ^ ecs[b1];
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}
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errl = bch[synd] >> 12;
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} else {
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errl = 3;
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}
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if (errl == 1) pari = pari ^ 0x01;
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}
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if (errl == 4) errl = 3;
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return errl;
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}
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bool pocsag_decode_batch(const POCSAGPacket& batch, POCSAGState& state) {
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constexpr uint8_t codeword_max = 16;
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state.output.clear();
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while (state.codeword_index < codeword_max) {
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auto codeword = batch[state.codeword_index];
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bool is_address = (codeword & 0x80000000U) == 0;
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// Error correct twice. First time to fix any errors it can,
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// second time to count number of errors that couldn't be fixed.
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state.ecc->error_correct(codeword);
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auto error_count = state.ecc->error_correct(codeword);
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switch (state.mode) {
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case STATE_CLEAR:
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if (is_address && codeword != POCSAG_IDLEWORD) {
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state.function = (codeword >> 11) & 3;
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state.address = (codeword >> 10) & 0x1FFFF8U; // 18 MSBs are transmitted
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state.mode = STATE_HAVE_ADDRESS;
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state.out_type = ADDRESS;
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state.errors = error_count;
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state.ascii_idx = 0;
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state.ascii_data = 0;
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} else if (codeword == POCSAG_IDLEWORD) {
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state.out_type = IDLE;
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}
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break;
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case STATE_HAVE_ADDRESS:
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if (is_address) {
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// Got another address, return the current state.
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state.mode = STATE_CLEAR;
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return true;
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}
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// First message codeword, complete the address.
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state.address |= (state.codeword_index >> 1); // Add in the 3 LSBs (frame #).
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state.mode = STATE_GETTING_MSG;
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[[fallthrough]];
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case STATE_GETTING_MSG:
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if (is_address) {
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// Codeword isn't a message, return the current state.
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state.mode = STATE_CLEAR;
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return true;
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}
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state.out_type = MESSAGE;
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state.errors += error_count;
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state.ascii_data |= (codeword >> 11) & 0xFFFFF; // Get 20 message bits.
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state.ascii_idx += 20;
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// Raw 20 bits to 7 bit reversed ASCII.
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// NB: This is processed MSB first, any remaining bits are shifted
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// up so a whole 7 bits are processed with the next codeword.
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while (state.ascii_idx >= 7) {
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state.ascii_idx -= 7;
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char ascii_char = (state.ascii_data >> state.ascii_idx) & 0x7F;
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// Bottom's up (reverse the bits).
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ascii_char = (ascii_char & 0xF0) >> 4 | (ascii_char & 0x0F) << 4; // 01234567 -> 45670123
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ascii_char = (ascii_char & 0xCC) >> 2 | (ascii_char & 0x33) << 2; // 45670123 -> 67452301
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ascii_char = (ascii_char & 0xAA) >> 2 | (ascii_char & 0x55); // 67452301 -> 76543210
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// Translate non-printable chars. TODO: Leave CRLF?
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if (ascii_char < 32 || ascii_char > 126)
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state.output += ".";
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else
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state.output += ascii_char;
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}
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state.ascii_data <<= 20; // Remaining bits are for next iteration...
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break;
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}
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state.codeword_index++;
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}
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return false;
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}
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} /* namespace pocsag */
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