mirror of
https://github.com/portapack-mayhem/mayhem-firmware.git
synced 2024-12-13 11:44:31 +00:00
05df04df7e
For now, shows only for Schrader OOK packets: top (left) nibble is function code, bottom nibble has two-bit checksum.
135 lines
3.3 KiB
C++
135 lines
3.3 KiB
C++
/*
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* Copyright (C) 2015 Jared Boone, ShareBrained Technology, Inc.
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*
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* This file is part of PortaPack.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2, or (at your option)
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* any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; see the file COPYING. If not, write to
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* the Free Software Foundation, Inc., 51 Franklin Street,
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* Boston, MA 02110-1301, USA.
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*/
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#include "tpms_packet.hpp"
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#include "crc.hpp"
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namespace tpms {
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Timestamp Packet::received_at() const {
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return packet_.timestamp();
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}
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ManchesterFormatted Packet::symbols_formatted() const {
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return format_manchester(decoder_);
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}
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Optional<Reading> Packet::reading(const SignalType signal_type) const {
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if( signal_type == SignalType::FLM ) {
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const auto length = crc_valid_length();
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switch(length) {
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case 64:
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return Reading {
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Reading::Type::FLM_64,
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reader_.read(0, 32),
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Pressure { static_cast<int>(reader_.read(32, 8)) * 4 / 3 },
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Temperature { static_cast<int>(reader_.read(40, 8) & 0x7f) - 50 }
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};
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case 72:
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return Reading {
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Reading::Type::FLM_72,
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reader_.read(0, 32),
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Pressure { static_cast<int>(reader_.read(40, 8)) * 4 / 3 },
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Temperature { static_cast<int>(reader_.read(48, 8)) - 50 }
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};
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case 80:
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return Reading {
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Reading::Type::FLM_80,
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reader_.read(8, 32),
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Pressure { static_cast<int>(reader_.read(48, 8)) * 4 / 3 },
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Temperature { static_cast<int>(reader_.read(56, 8)) - 50 }
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};
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default:
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return { };
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}
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}
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if( signal_type == SignalType::Schrader ) {
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const auto flags = reader_.read(0, 3);
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const auto checksum = reader_.read(35, 2);
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return Reading {
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Reading::Type::Schrader,
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reader_.read(3, 24),
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Pressure { static_cast<int>(reader_.read(27, 8)) * 4 / 3 },
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{ },
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Flags { (flags << 4) | checksum }
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};
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}
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if( signal_type == SignalType::GMC ) {
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return Reading {
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Reading::Type::GMC_96,
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reader_.read(20, 32),
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Pressure { static_cast<int>(reader_.read(52, 8)) }
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};
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}
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return { };
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}
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size_t Packet::crc_valid_length() const {
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constexpr uint32_t checksum_bytes = 0b1111111;
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constexpr uint32_t crc_72_bytes = 0b111111111;
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constexpr uint32_t crc_80_bytes = 0b1111111110;
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std::array<uint8_t, 10> bytes;
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for(size_t i=0; i<bytes.size(); i++) {
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bytes[i] = reader_.read(i * 8, 8);
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}
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uint32_t checksum = 0;
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CRC<8> crc_72 { 0x01, 0x00 };
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CRC<8> crc_80 { 0x01, 0x00 };
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for(size_t i=0; i<bytes.size(); i++) {
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const uint32_t byte_mask = 1 << i;
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const auto byte = bytes[i];
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if( checksum_bytes & byte_mask ) {
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checksum += byte;
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}
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if( crc_72_bytes & byte_mask ) {
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crc_72.process_byte(byte);
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}
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if( crc_80_bytes & byte_mask ) {
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crc_80.process_byte(byte);
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}
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}
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if( crc_80.checksum() == 0 ) {
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return 80;
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} else if( crc_72.checksum() == 0 ) {
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return 72;
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} else if( (checksum & 0xff) == bytes[7] ) {
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return 64;
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} else {
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return 0;
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}
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}
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} /* namespace tpms */
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