portapack-mayhem/firmware/application/rfm69.cpp
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C++

/*
* Copyright (C) 2017 Jared Boone, ShareBrained Technology, Inc.
* Copyright (C) 2019 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 "rfm69.hpp"
#include "crc.hpp"
#include "portapack_shared_memory.hpp"
uint32_t RFM69::gen_frame(std::vector<uint8_t>& payload) {
CRC<16> crc{0x1021, 0x1D0F, 0xFFFF};
std::vector<uint8_t> frame{};
uint8_t byte_out = 0;
// Preamble
// Really is 0xAA but the RFM69 skips the very last bit (bug ?)
// so the whole preamble is shifted right to simulate that
frame.insert(frame.begin(), num_preamble_, 0x55);
// Sync word
frame.push_back(sync_word_ >> 8);
frame.push_back(sync_word_ & 0xFF);
// Payload length
payload.insert(payload.begin(), payload.size());
crc.process_bytes(payload.data(), payload.size());
if (CRC_) {
payload.push_back(crc.checksum() >> 8);
payload.push_back(crc.checksum() & 0xFF);
}
// Manchester-encode payload
if (manchester_) {
for (auto byte : payload) {
for (uint32_t b = 0; b < 8; b++) {
byte_out <<= 2;
if (byte & 0x80)
byte_out |= 0b10;
else
byte_out |= 0b01;
if ((b & 3) == 3)
frame.push_back(byte_out);
byte <<= 1;
}
}
} else {
frame.insert(frame.end(), payload.begin(), payload.end());
}
memcpy(shared_memory.bb_data.data, frame.data(), frame.size());
// Copy for baseband
return frame.size();
}