/* * Copyright (C) 2015 Jared Boone, ShareBrained Technology, Inc. * Copyright (C) 2017 Furrtek * Copyright (C) 2014 zilog80 * Copyright (C) 2024 Mark Thompson * * 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. */ /* Notes to self (or others, welcome !): * Sharebrained wrote in matched_filter.hpp that taps should be those of a complex low-pass filter combined with a complex sinusoid, so * that the filter shifts the spectrum where we want (signal of interest around 0Hz). * * In this baseband processor, after decim_0 and decim_1, the signal ends up being sampled at 38400Hz (2457600 / 8 / 8) * Since the applied shift in ui_sonde.cpp is -fs/4 = -2457600/4 = -614400Hz to avoid the DC spike, the FSK signal ends up being * shifted by 614400 / 8 / 8 = 9600Hz. So decim_1_out should look like this: * * _______________|______/'\______ * -C A B C * * A is the DC spike at 0Hz * B is the FSK signal shifted right at 9600Hz * C is the bandwidth edge at 19200Hz * * Taps should be computed to shift the whole spectrum by -9600Hz ("left") so that it looks like this: * * ______________/'\______________ * -C D C * * Anything unwanted (like A) should have been filtered off * D is B around 0Hz now * * Then the clock_recovery function should be happy :) * * Mathworks.com says: * In the case of a single-rate FIR design, we simply multiply each set of coefficients by (aka 'heterodyne with') a complex exponential. * * Can SciPy's remez function be used for this ? See tools/firtest.py * GnuRadio's firdes only outputs an odd number of taps * * --------------------------------------------------------------------- * * Looking at the AIS baseband processor: * * Copied everything necessary to get decim_1_out (so same 8 * 8 = 64 decimation factor) * The samplerate is also the same (2457600) * After the matching filter, the data is decimated by 2 so the final samplerate for clock_recovery is 38400 / 2 = 19200Hz. * Like here, the shift used is fs/4, so decim_1_out should be looking similar. * The AIS signal deviates by 2400 (4800Hz signal width), the symbol rate is 9600. * * The matched filter's input samplerate is 38400Hz, to get a 9600Hz shift it must use 4 taps ? * To obtain unity gain, the sinusoid length must be / by the number of taps ? * * See ais_baseband.hpp * * */ #ifndef __PROC_SONDE_H__ #define __PROC_SONDE_H__ #include "baseband_processor.hpp" #include "baseband_thread.hpp" #include "rssi_thread.hpp" #include "proc_ais.hpp" #include "channel_decimator.hpp" #include "matched_filter.hpp" #include "clock_recovery.hpp" #include "symbol_coding.hpp" #include "packet_builder.hpp" #include "baseband_packet.hpp" #include "message.hpp" #include "portapack_shared_memory.hpp" #include "buffer.hpp" #include #include #include #define BEEP_MIN_DURATION 60 #define BEEP_DURATION_RANGE 100 #define BEEP_BASE_FREQ 200 #define RSSI_CEILING 1000 #define PROPORTIONAL_BEEP_THRES 0.8 #define RSSI_PITCH_WEIGHT 0.5 #define AUDIO_SAMPLE_RATE 24000 class SondeProcessor : public BasebandProcessor { public: SondeProcessor(); void execute(const buffer_c8_t& buffer) override; void on_message(const Message* const msg); private: static constexpr size_t baseband_fs = 2457600; bool pitch_rssi_enabled{false}; uint32_t last_rssi{0}; uint32_t beep_freq{0}; std::array dst{}; const buffer_c16_t dst_buffer{ dst.data(), dst.size()}; dsp::decimate::FIRC8xR16x24FS4Decim8 decim_0{}; dsp::decimate::FIRC16xR16x32Decim8 decim_1{}; dsp::matched_filter::MatchedFilter mf{baseband::ais::square_taps_38k4_1t_p, 2}; // Actually 4800bits/s but the Manchester coding doubles the symbol rate clock_recovery::ClockRecovery clock_recovery_fsk_9600{ 19200, 9600, {0.0555f}, [this](const float raw_symbol) { const uint_fast8_t sliced_symbol = (raw_symbol >= 0.0f) ? 1 : 0; this->packet_builder_fsk_9600_Meteomodem.execute(sliced_symbol); }}; PacketBuilder packet_builder_fsk_9600_Meteomodem{ {0b00110011001100110101100110110011, 32, 1}, {}, {88 * 2 * 8}, [this](const baseband::Packet& packet) { const SondePacketMessage message{sonde::Packet::Type::Meteomodem_unknown, packet}; shared_memory.application_queue.push(message); }}; clock_recovery::ClockRecovery clock_recovery_fsk_4800{ 19200, 4800, {0.0555f}, [this](const float raw_symbol) { const uint_fast8_t sliced_symbol = (raw_symbol >= 0.0f) ? 1 : 0; this->packet_builder_fsk_4800_Vaisala.execute(sliced_symbol); }}; PacketBuilder packet_builder_fsk_4800_Vaisala{ {0b00001000011011010101001110001000, 32, 1}, // euquiq Header detects 4 of 8 bytes 0x10B6CA11 /this is in raw format) (these bits are not passed at the beginning of packet) //{ 0b0000100001101101010100111000100001000100011010010100100000011111, 64, 1 }, //euquiq whole header detection would be 8 bytes. {}, {320 * 8}, [this](const baseband::Packet& packet) { const SondePacketMessage message{sonde::Packet::Type::Vaisala_RS41_SG, packet}; shared_memory.application_queue.push(message); }}; /* NB: Threads should be the last members in the class definition. */ BasebandThread baseband_thread{ baseband_fs, this, baseband::Direction::Receive, /*auto_start*/ false}; RSSIThread rssi_thread{}; void pitch_rssi_config(const PitchRSSIConfigureMessage& message); }; #endif /*__PROC_ERT_H__*/