Git-Mirrors/portapack-mayhem
1
0
Fork 0
mirror of https://github.com/eried/portapack-mayhem.git synced 2024-10-01 01:26:06 -04:00
Code Issues Packages Projects Releases Wiki Activity

TPMS: Validate checksum for the OOK 8k4 Schrader variant.

Browse Source
This commit is contained in:
Jared Boone 2016-06-02 22:22:22 -07:00
parent 4734790518
commit 9628815da7
1 changed files with 33 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

38
firmware/common/tpms_packet.cpp
View File

@ -80,11 +80,39 @@ Optional<Reading> Packet::reading_ook_8k192_schrader() const {
} }
Optional<Reading> Packet::reading_ook_8k4_schrader() const { Optional<Reading> Packet::reading_ook_8k4_schrader() const {
return Reading { /*
Reading::Type::GMC_96, * Preamble: 01*40
reader_.read(20, 32), * System ID: 01100101, ??*20 (not really sure what this data is)
Pressure { static_cast<int>(reader_.read(52, 8)) } * ID: 32 Manchester symbols
}; * Value: 8 Manchester symbols (temperature?)
* Value: 8 Manchester symbols (pressure?)
* 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,
id,
Pressure { static_cast<int>(value_1) * 4 / 3 },
Temperature { static_cast<int>(value_0) - 50 }
};
} else {
return { };
}
} }
Optional<Reading> Packet::reading() const { Optional<Reading> Packet::reading() const {