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Check TPMS CRCs for packets I know, don't display the rest.

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This commit is contained in:
Jared Boone 2016-01-18 20:43:54 -08:00
parent fbcf784959
commit dbea30b9e4
2 changed files with 58 additions and 4 deletions
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50
firmware/application/tpms_app.cpp
View File

@ -28,6 +28,8 @@ using namespace portapack;
#include "string_format.hpp"
#include "crc.hpp"
namespace tpms {
Timestamp Packet::received_at() const {
@ -38,6 +40,46 @@ ManchesterFormatted Packet::symbols_formatted() const {
return format_manchester(decoder_);
}
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 = 6;
CRC<uint8_t> crc_72 { 0x01, 0xff };
CRC<uint8_t> crc_80 { 0x01, 0xff };
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 */
void TPMSLogger::on_packet(const tpms::Packet& packet) {
@ -91,8 +133,12 @@ void TPMSAppView::on_packet(const tpms::Packet& packet) {
}
void TPMSAppView::draw(const tpms::Packet& packet) {
const auto hex_formatted = packet.symbols_formatted();
console.writeln(hex_formatted.data.substr(0, 240 / 8));
const auto packet_length = packet.crc_valid_length();
if( packet_length > 0 ) {
const size_t length_chars = packet_length * 2 / 8;
const auto hex_formatted = packet.symbols_formatted();
console.writeln(hex_formatted.data.substr(0, length_chars));
}
}
} /* namespace ui */

12
firmware/application/tpms_app.hpp
View File

@ -23,8 +23,9 @@
#define __TPMS_APP_H__
#include "ui_console.hpp"
#include "message.hpp"
#include "field_reader.hpp"
#include "baseband_packet.hpp"
#include "manchester.hpp"
#include "log_file.hpp"
@ -35,7 +36,8 @@ public:
constexpr Packet(
const baseband::Packet& packet
) : packet_ { packet },
decoder_ { packet_, 1 }
decoder_ { packet_, 1 },
reader_ { decoder_ }
{
}
@ -43,9 +45,15 @@ public:
ManchesterFormatted symbols_formatted() const;
size_t crc_valid_length() const;
private:
using Reader = FieldReader<ManchesterDecoder, BitRemapNone>;
const baseband::Packet packet_;
const ManchesterDecoder decoder_;
const Reader reader_;
};
} /* namespace tpms */