mayhem-firmware/firmware/baseband/proc_rds.cpp

/*
 * 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_rds.hpp"
#include "portapack_shared_memory.hpp"
#include "sine_table_int8.hpp"
#include "event_m4.hpp"

#include <cstdint>

void RDSProcessor::execute(const buffer_c8_t& buffer) {
    for (size_t i = 0; i < buffer.count; i++) {
        // Sample generation at 2.28M / 10 = 228kHz
        if (s >= 9) {
            s = 0;
            if (sample_count >= SAMPLES_PER_BIT) {
                if (bit_pos >= message_length) {
                    bit_pos = 0;
                    cur_output = 0;
                }

                cur_bit = (rdsdata[(bit_pos / 26) & 127] >> (25 - (bit_pos % 26))) & 1;
                prev_output = cur_output;
                cur_output = prev_output ^ cur_bit;

                const int32_t* src = waveform_biphase;
                int idx = in_sample_index;

                for (int j = 0; j < FILTER_SIZE; j++) {
                    val = (*src++);
                    if (cur_output) val = -val;
                    sample_buffer[idx++] += val;
                    if (idx >= SAMPLE_BUFFER_SIZE) idx = 0;
                }

                in_sample_index += SAMPLES_PER_BIT;
                if (in_sample_index >= SAMPLE_BUFFER_SIZE) in_sample_index -= SAMPLE_BUFFER_SIZE;

                bit_pos++;

                sample_count = 0;
            }

            sample = sample_buffer[out_sample_index];
            sample_buffer[out_sample_index] = 0;
            out_sample_index++;
            if (out_sample_index >= SAMPLE_BUFFER_SIZE) out_sample_index = 0;

            // AM @ 228k/4 = 57kHz
            // 0, sample, 0, -sample...
            switch (mphase & 3) {
                case 0:
                case 2:
                    sample = 0;
                    break;
                case 1:
                    break;
                case 3:
                    sample = -sample;  // break;
            }
            mphase++;

            sample_count++;
        } else {
            s++;
        }

        // FM
        delta = (sample >> 16) * 386760;  // ?

        phase += delta;
        sphase = phase + (64 << 18);

        re = (sine_table_i8[(sphase & 0x03FF0000) >> 18]);
        im = (sine_table_i8[(phase & 0x03FF0000) >> 18]);

        buffer.p[i] = {re, im};
    }
}

void RDSProcessor::on_message(const Message* const msg) {
    if (msg->id == Message::ID::RDSConfigure) {
        const auto message = *reinterpret_cast<const RDSConfigureMessage*>(msg);
        rdsdata = (uint32_t*)shared_memory.bb_data.data;
        message_length = message.length;
        configured = true;
    }
}

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