mayhem-firmware/firmware/baseband/proc_nrfrx.cpp

/*
 * Copyright (C) 2015 Jared Boone, ShareBrained Technology, Inc.
 * Copyright (C) 2016 Furrtek
 * Copyright (C) 2020 Shao
 *
 * 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_nrfrx.hpp"
#include "portapack_shared_memory.hpp"

#include "event_m4.hpp"

void NRFRxProcessor::execute(const buffer_c8_t& buffer) {
    if (!configured) return;

    // FM demodulation

    const auto decim_0_out = decim_0.execute(buffer, dst_buffer);
    feed_channel_stats(decim_0_out);

    auto audio_oversampled = demod.execute(decim_0_out, work_audio_buffer);
    // Audio signal processing
    for (size_t c = 0; c < audio_oversampled.count; c++) {
        int g_srate = 4;  // 4 for 250KPS
        // int g_srate = 1; //1 for 1MPS, not working yet
        int32_t current_sample = audio_oversampled.p[c];  // if I directly use this, some results can pass crc but not correct.
        rb_head++;
        rb_head = (rb_head) % RB_SIZE;

        rb_buf[rb_head] = current_sample;

        skipSamples = skipSamples - 1;

        if (skipSamples < 1) {
            int32_t threshold_tmp = 0;
            for (int c = 0; c < 8 * g_srate; c++) {
                threshold_tmp = threshold_tmp + (int32_t)rb_buf[(rb_head + c) % RB_SIZE];
            }

            g_threshold = (int32_t)threshold_tmp / (8 * g_srate);

            int transitions = 0;
            if (rb_buf[(rb_head + 9 * g_srate) % RB_SIZE] > g_threshold) {
                for (int c = 0; c < 8; c++) {
                    if (rb_buf[(rb_head + c * g_srate) % RB_SIZE] > rb_buf[(rb_head + (c + 1) * g_srate) % RB_SIZE])
                        transitions = transitions + 1;
                }
            } else {
                for (int c = 0; c < 8; c++) {
                    if (rb_buf[(rb_head + c * g_srate) % RB_SIZE] < rb_buf[(rb_head + (c + 1) * g_srate) % RB_SIZE])
                        transitions = transitions + 1;
                }
            }

            bool packet_detected = false;
            // if ( transitions==4 && abs(g_threshold)<15500)
            if (transitions == 4 && abs(g_threshold) < 15500) {
                int packet_length = 0;
                uint8_t tmp_buf[10];
                uint8_t packet_data[500];
                uint8_t packet_packed[50];
                uint16_t pcf;
                uint32_t packet_crc;
                uint32_t calced_crc;
                uint64_t packet_addr_l;

                /* extract address */
                packet_addr_l = 0;

                for (int t = 0; t < 5; t++) {
                    bool current_bit;
                    uint8_t byte = 0;
                    for (int c = 0; c < 8; c++) {
                        if (rb_buf[(rb_head + (1 * 8 + t * 8 + c) * g_srate) % RB_SIZE] > g_threshold)
                            current_bit = true;
                        else
                            current_bit = false;
                        byte |= current_bit << (7 - c);
                    }
                    tmp_buf[t] = byte;
                }

                for (int t = 0; t < 5; t++) packet_addr_l |= ((uint64_t)tmp_buf[t]) << (4 - t) * 8;

                // channel_number = 26;

                /* extract pcf */
                for (int t = 0; t < 2; t++) {
                    bool current_bit;
                    uint8_t byte = 0;
                    for (int c = 0; c < 8; c++) {
                        if (rb_buf[(rb_head + (6 * 8 + t * 8 + c) * g_srate) % RB_SIZE] > g_threshold)
                            current_bit = true;
                        else
                            current_bit = false;
                        byte |= current_bit << (7 - c);
                    }
                    tmp_buf[t] = byte;
                }

                pcf = tmp_buf[0] << 8 | tmp_buf[1];
                pcf >>= 7;

                /* extract packet length, avoid excessive length packets */
                if (packet_length == 0)
                    packet_length = (int)pcf >> 3;
                if (packet_length > 32)
                    packet_detected = false;

                /* extract data */
                for (int t = 0; t < packet_length; t++) {
                    bool current_bit;
                    uint8_t byte = 0;
                    for (int c = 0; c < 8; c++) {
                        if (rb_buf[(rb_head + (6 * 8 + 9 + t * 8 + c) * g_srate) % RB_SIZE] > g_threshold)
                            current_bit = true;
                        else
                            current_bit = false;
                        byte |= current_bit << (7 - c);
                    }
                    packet_data[t] = byte;
                }

                /* Prepare packed bit stream for CRC calculation */
                uint64_t packet_header = packet_addr_l;
                packet_header <<= 9;
                packet_header |= pcf;
                for (int c = 0; c < 7; c++) {
                    packet_packed[c] = (packet_header >> ((6 - c) * 8)) & 0xFF;
                }

                for (int c = 0; c < packet_length; c++) {
                    packet_packed[c + 7] = packet_data[c];
                }

                /* calculate packet crc */
                const uint8_t* data = packet_packed;
                size_t data_len = 7 + packet_length;
                bool bit;
                uint8_t cc;
                uint_fast16_t crc = 0x3C18;
                while (data_len--) {
                    cc = *data++;
                    for (uint8_t i = 0x80; i > 0; i >>= 1) {
                        bit = crc & 0x8000;
                        if (cc & i) {
                            bit = !bit;
                        }
                        crc <<= 1;
                        if (bit) {
                            crc ^= 0x1021;
                        }
                    }
                    crc &= 0xffff;
                }
                calced_crc = (uint16_t)(crc & 0xffff);

                /* extract crc */
                for (int t = 0; t < 2; t++) {
                    bool current_bit;
                    uint8_t byte = 0;
                    for (int c = 0; c < 8; c++) {
                        if (rb_buf[(rb_head + ((6 + packet_length) * 8 + 9 + t * 8 + c) * g_srate) % RB_SIZE] > g_threshold)
                            current_bit = true;
                        else
                            current_bit = false;
                        byte |= current_bit << (7 - c);
                    }
                    tmp_buf[t] = byte;
                }
                packet_crc = tmp_buf[0] << 8 | tmp_buf[1];

                /* NRF24L01+ packet found, dump information */
                // if (packet_addr_l==0xE7E7E7E7)
                if (packet_crc == calced_crc) {
                    data_message.is_data = false;
                    data_message.value = 'A';
                    shared_memory.application_queue.push(data_message);

                    data_message.is_data = true;
                    data_message.value = packet_addr_l;
                    shared_memory.application_queue.push(data_message);

                    for (int c = 0; c < 7; c++) {
                        data_message.is_data = true;
                        data_message.value = packet_addr_l >> 8;
                        shared_memory.application_queue.push(data_message);
                    }
                    /*data_message.is_data = true;
                                        data_message.value = packet_addr_l;
                                        shared_memory.application_queue.push(data_message);

                                        data_message.is_data = true;
                                        data_message.value = packet_addr_l >> 8;
                                        shared_memory.application_queue.push(data_message);*/

                    data_message.is_data = false;
                    data_message.value = 'B';
                    shared_memory.application_queue.push(data_message);

                    for (int c = 0; c < packet_length; c++) {
                        data_message.is_data = true;
                        data_message.value = packet_data[c];
                        shared_memory.application_queue.push(data_message);
                    }

                    data_message.is_data = false;
                    data_message.value = 'C';
                    shared_memory.application_queue.push(data_message);

                    packet_detected = true;
                } else
                    packet_detected = false;
            }

            if (packet_detected) {
                skipSamples = 20;
            }
        }
    }
}

void NRFRxProcessor::on_message(const Message* const message) {
    if (message->id == Message::ID::NRFRxConfigure)
        configure(*reinterpret_cast<const NRFRxConfigureMessage*>(message));
}

void NRFRxProcessor::configure(const NRFRxConfigureMessage& message) {
    (void)message;  // avoir unused warning
    decim_0.configure(taps_200k_wfm_decim_0.taps, 33554432);
    decim_1.configure(taps_200k_wfm_decim_1.taps, 131072);
    demod.configure(audio_fs, 5000);

    configured = true;
}

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