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TPMS: Validate checksum for OOK 8k192 Schrader.

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This commit is contained in:
Jared Boone 2016-06-02 23:09:55 -07:00
parent 9628815da7
commit a475daeeea
1 changed files with 23 additions and 7 deletions
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30
firmware/common/tpms_packet.cpp
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@ -67,16 +67,32 @@ Optional<Reading> Packet::reading_fsk_19k2_schrader() const {
}
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);
return Reading {
Reading::Type::Schrader,
reader_.read(3, 24),
Pressure { static_cast<int>(reader_.read(27, 8)) * 4 / 3 },
{ },
Flags { (flags << 4) | checksum }
};
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,
reader_.read(3, 24),
Pressure { static_cast<int>(reader_.read(27, 8)) * 4 / 3 },
{ },
Flags { (flags << 4) | checksum }
};
} else {
return { };
}
}
Optional<Reading> Packet::reading_ook_8k4_schrader() const {