portapack-mayhem/firmware/common/tpms_packet.cpp
2023-04-03 16:40:07 -05:00

184 lines
5.0 KiB
C++

/*
* Copyright (C) 2015 Jared Boone, ShareBrained Technology, Inc.
*
* 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 "tpms_packet.hpp"
#include "crc.hpp"
namespace tpms {
Timestamp Packet::received_at() const {
return packet_.timestamp();
}
FormattedSymbols Packet::symbols_formatted() const {
return format_symbols(decoder_);
}
Optional<Reading> Packet::reading_fsk_19k2_schrader() const {
const auto length = crc_valid_length();
switch(length) {
case 64:
return Reading {
Reading::Type::FLM_64,
(uint32_t)reader_.read(0, 32),
Pressure { static_cast<int>(reader_.read(32, 8)) * 4 / 3 },
Temperature { static_cast<int>(reader_.read(40, 8) & 0x7f) - 56 }
};
case 72:
return Reading {
Reading::Type::FLM_72,
(uint32_t)reader_.read(0, 32),
Pressure { static_cast<int>(reader_.read(40, 8)) * 4 / 3 },
Temperature { static_cast<int>(reader_.read(48, 8)) - 56 }
};
case 80:
return Reading {
Reading::Type::FLM_80,
(uint32_t)reader_.read(8, 32),
Pressure { static_cast<int>(reader_.read(48, 8)) * 4 / 3 },
Temperature { static_cast<int>(reader_.read(56, 8)) - 56 }
};
default:
return { };
}
}
Optional<Reading> Packet::reading_ook_8k192_schrader() const {
/*
* Preamble: 11*2, 01*14, 11, 10
* Function code: 3 Manchester symbols
* ID: 24 Manchester symbols (one variant seen with 21 symbols?)
* Pressure: 8 Manchester symbols
* Checksum: 2 Manchester symbols (2 LSBs of sum incl this field == 3)
*/
const auto flags = reader_.read(0, 3);
const auto checksum = reader_.read(35, 2);
uint32_t checksum_calculated = reader_.read(0, 1);
for(size_t i=1; i<37; i+=2) {
checksum_calculated += reader_.read(i, 2);
}
if( (checksum_calculated & 3) == 3 ) {
return Reading {
Reading::Type::Schrader,
(uint32_t)reader_.read(3, 24),
Pressure { static_cast<int>(reader_.read(27, 8)) * 4 / 3 },
{ },
Flags { static_cast<Flags>((flags << 4) | checksum) }
};
} else {
return { };
}
}
Optional<Reading> Packet::reading_ook_8k4_schrader() const {
/*
* Preamble: 01*40
* System ID: 01100101, ??*20 (not really sure what this data is)
* ID: 32 Manchester symbols
* Value: 8 Manchester symbols (pressure)
* Value: 8 Manchester symbols (temperature)
* Checksum: 8 Manchester symbols (uint8_t sum of bytes starting with system ID)
*/
/* NOTE: First four bits of packet are consumed in preamble detection.
* Those bits assumed to be 0b0100", which may not be entirely true...
*/
constexpr uint8_t first_nibble = 0x4;
// const auto system_id = (first_nibble << 20) | reader_.read(0, 20);
const auto id = reader_.read(20, 32);
const auto value_0 = reader_.read(52, 8);
const auto value_1 = reader_.read(60, 8);
const auto checksum = reader_.read(68, 8);
uint8_t checksum_calculated = (first_nibble << 4) | reader_.read(0, 4);
for(size_t i=4; i<68; i+=8) {
checksum_calculated += reader_.read(i, 8);
}
if( checksum_calculated == checksum ) {
return Reading {
Reading::Type::GMC_96,
(uint32_t)id,
Pressure { static_cast<int>(value_0) * 11 / 4 },
Temperature { static_cast<int>(value_1) - 61 }
};
} else {
return { };
}
}
Optional<Reading> Packet::reading() const {
switch( signal_type() ) {
case SignalType::FSK_19k2_Schrader: return reading_fsk_19k2_schrader();
case SignalType::OOK_8k192_Schrader: return reading_ook_8k192_schrader();
case SignalType::OOK_8k4_Schrader: return reading_ook_8k4_schrader();
default: return { };
}
}
size_t Packet::crc_valid_length() const {
constexpr uint32_t checksum_bytes = 0b1111111;
constexpr uint32_t crc_72_bytes = 0b111111111;
constexpr uint32_t crc_80_bytes = 0b1111111110;
std::array<uint8_t, 10> bytes;
for(size_t i=0; i<bytes.size(); i++) {
bytes[i] = reader_.read(i * 8, 8);
}
uint32_t checksum = 0;
CRC<8> crc_72 { 0x01, 0x00 };
CRC<8> crc_80 { 0x01, 0x00 };
for(size_t i=0; i<bytes.size(); i++) {
const uint32_t byte_mask = 1 << i;
const auto byte = bytes[i];
if( checksum_bytes & byte_mask ) {
checksum += byte;
}
if( crc_72_bytes & byte_mask ) {
crc_72.process_byte(byte);
}
if( crc_80_bytes & byte_mask ) {
crc_80.process_byte(byte);
}
}
if( crc_80.checksum() == 0 ) {
return 80;
} else if( crc_72.checksum() == 0 ) {
return 72;
} else if( (checksum & 0xff) == bytes[7] ) {
return 64;
} else {
return 0;
}
}
} /* namespace tpms */