portapack-mayhem/firmware/baseband/proc_adsbtx.cpp

/*
 * Copyright (C) 2014 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_adsbtx.hpp"
#include "portapack_shared_memory.hpp"
#include "sine_table_int8.hpp"
#include "event_m4.hpp"

#include <cstdint>

void ADSBTXProcessor::execute(const buffer_c8_t& buffer) {
    // This is called at 4M/2048 = 1953Hz
    // One pulse = 500ns = 2 samples
    // One bit = 2 pulses = 1us = 4 samples
    // Test this with ./dump1090 --freq 434000000 --gain 20
    // Or ./dump1090 --freq 434000000 --gain 20 --interactive --net --net-http-port 8080 --net-beast

    if (!configured) return;

    for (size_t i = 0; i < buffer.count; i++) {
        if (bit_pos >= (240 << 1)) {
            configured = false;
            cur_bit = 0;
        } else {
            cur_bit = shared_memory.bb_data.data[bit_pos >> 1];
            bit_pos++;
        }

        if (cur_bit) {
            // Crude AM
            buffer.p[i] = am_lut[phase & 3];
            phase++;
        } else {
            buffer.p[i] = {0, 0};
        }
    }
}

void ADSBTXProcessor::on_message(const Message* const p) {
    const auto message = *reinterpret_cast<const ADSBConfigureMessage*>(p);

    if (message.id == Message::ID::ADSBConfigure) {
        bit_pos = 0;
        phase = 0;
        configured = true;
    }
}

int main() {
    EventDispatcher event_dispatcher{std::make_unique<ADSBTXProcessor>()};
    event_dispatcher.run();
    return 0;
}