portapack-mayhem/firmware/baseband/proc_pocsag.cpp

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/*
* Copyright (C) 1996 Thomas Sailer (sailer@ife.ee.ethz.ch, hb9jnx@hb9w.che.eu)
* Copyright (C) 2012-2014 Elias Oenal (multimon-ng@eliasoenal.com)
* Copyright (C) 2015 Jared Boone, ShareBrained Technology, Inc.
* Copyright (C) 2016 Furrtek
*
* This file is part of PortaPack.
*
* 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 2, 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; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street,
* Boston, MA 02110-1301, USA.
*/
#include "proc_pocsag.hpp"
#include "event_m4.hpp"
#include <cstdint>
#include <cstddef>
#define FREQ_SAMP 24000
#define BAUD 1200
#define SPHASEINC (0x10000u * BAUD / FREQ_SAMP)
#define POCSAG_SYNC 0x7CD215D8
#define POCSAG_IDLE 0x7A89C197
void POCSAGProcessor::execute(const buffer_c8_t& buffer) {
/* 1.536MHz, 2048 samples */
if( !configured ) return;
const auto decim_0_out = decim_0.execute(buffer, dst_buffer);
const auto decim_1_out = decim_1.execute(decim_0_out, dst_buffer);
auto audio = demod.execute(decim_1_out, audio_buffer);
for (c = 0; c < 32; c++) {
// Bit = sign
const int32_t audio_sample = audio.p[c] * 32768.0f; // sample_int
//const int32_t audio_sample = __SSAT(sample_int, 16);
dcd_shreg <<= 1;
dcd_shreg |= (audio_sample < 0);
// Detect transitions to adjust clock
if ((dcd_shreg ^ (dcd_shreg >> 1)) & 1) {
if (sphase < (0x8000u-(SPHASEINC/2)))
sphase += SPHASEINC/8;
else
sphase -= SPHASEINC/8;
}
sphase += SPHASEINC;
if (sphase >= 0x10000u) {
sphase &= 0xffffu;
rx_data <<= 1;
rx_data |= (dcd_shreg & 1);
switch(rx_state) {
case WAITING:
if (rx_data == 0xAAAAAAAA) {
rx_state = PREAMBLE;
sync_timeout = 0;
}
break;
case PREAMBLE:
if (sync_timeout < 600) {
sync_timeout++;
//pocsag_brute_repair(&s->l2.pocsag, &rx_data);
if (rx_data == POCSAG_SYNC) {
packet.clear();
frame_counter = 0;
rx_bit = 0;
msg_timeout = 0;
last_rx_data = rx_data;
rx_state = SYNC;
} else if (rx_data == POCSAG_IDLE) {
rx_state = WAITING;
}
} else {
rx_state = WAITING; // Abort
}
break;
case SYNC:
if (msg_timeout < 600) {
msg_timeout++;
rx_bit++;
if (rx_bit >= 32) {
rx_bit = 0;
//pocsag_brute_repair(&s->l2.pocsag, &rx_data);
packet.set(frame_counter, rx_data);
if ((rx_data == POCSAG_IDLE) && (!(last_rx_data & 0x80000000))) {
// SYNC then IDLE always means end of message ?
packet.set_bitrate(pocsag::BitRate::FSK1200);
packet.set_flag(pocsag::PacketFlag::NORMAL);
packet.set_timestamp(Timestamp::now());
const POCSAGPacketMessage message(packet);
shared_memory.application_queue.push(message);
rx_state = WAITING;
} else {
if (frame_counter < 15) {
frame_counter++;
} else {
// More than 17-1 codewords
packet.set_bitrate(pocsag::BitRate::FSK1200);
packet.set_flag(pocsag::PacketFlag::TOO_LONG);
packet.set_timestamp(Timestamp::now());
const POCSAGPacketMessage message(packet);
shared_memory.application_queue.push(message);
rx_state = WAITING;
}
}
last_rx_data = rx_data;
}
} else {
// Timed out (no end of message received)
packet.set_bitrate(pocsag::BitRate::FSK1200);
packet.set_flag(pocsag::PacketFlag::TIMED_OUT);
packet.set_timestamp(Timestamp::now());
const POCSAGPacketMessage message(packet);
shared_memory.application_queue.push(message);
rx_state = WAITING;
}
break;
default:
break;
}
}
}
}
void POCSAGProcessor::on_message(const Message* const message) {
if (message->id == Message::ID::POCSAGConfigure)
configure(*reinterpret_cast<const POCSAGConfigureMessage*>(message));
}
void POCSAGProcessor::configure(const POCSAGConfigureMessage& message) {
(void)message;
constexpr size_t decim_0_input_fs = baseband_fs;
constexpr size_t decim_0_output_fs = decim_0_input_fs / decim_0.decimation_factor;
constexpr size_t decim_1_input_fs = decim_0_output_fs;
constexpr size_t decim_1_output_fs = decim_1_input_fs / decim_1.decimation_factor;
const size_t demod_input_fs = decim_1_output_fs;
decim_0.configure(taps_11k0_decim_0.taps, 33554432);
decim_1.configure(taps_11k0_decim_1.taps, 131072);
demod.configure(demod_input_fs, 4500);
rx_state = WAITING;
configured = true;
}
int main() {
EventDispatcher event_dispatcher { std::make_unique<POCSAGProcessor>() };
event_dispatcher.run();
return 0;
}