Crc8DallasMaxim Class Reference

Helper class for computing CRC-8 according to Dallas/Maxim specification for 1-wire protocol. More...

#include <Crc.hxx>

Public Member Functions
void	init ()
	Re-sets the state machine for checksumming a new message.
uint8_t	get ()
bool	check_ok ()
	Checks that the message has a correct CRC.
bool	check_ok (uint8_t checksum_byte)
	Checks that the message has a correct CRC.
void	update0 (uint8_t message_byte)
	Processes one byte of the incoming message.
void	update16 (uint8_t message_byte)
	Processes one byte of the incoming message.
void	update256 (uint8_t message_byte)
	Processes one byte of the incoming message.
void	update (uint8_t message_byte)
	Processes one byte of the incoming message.

Private Attributes
uint8_t	state_
	Current value of the state register for the CRC computation.

Static Private Attributes
static const uint8_t	table256 [256]
	256-entry lookup table for the update256 function.
static const uint8_t	tableHi16 [16]
	16-entry lookup table for the update16 function.
static const uint8_t	tableLo16 [16]
	16-entry lookup table for the update16 function.

Detailed Description

Helper class for computing CRC-8 according to Dallas/Maxim specification for 1-wire protocol.

This specification is used for BiDiB, RCN-218 and S-9.2.1.1.

This class can incrementally compute CRC byte by byte. There are three implementations available, with different code space requirements.

Definition at line 82 of file Crc.hxx.

Constructor & Destructor Documentation

Crc8DallasMaxim()

Crc8DallasMaxim::Crc8DallasMaxim ( )

inline

Definition at line 85 of file Crc.hxx.

Member Function Documentation

check_ok() [1/2]

bool Crc8DallasMaxim::check_ok ( )

inline

Checks that the message has a correct CRC.

This function assumes that the CRC byte has already been consumed.

Returns

true if the message checksum is correct.

Definition at line 105 of file Crc.hxx.

check_ok() [2/2]

bool Crc8DallasMaxim::check_ok ( uint8_t  checksum_byte )

inline

Checks that the message has a correct CRC.

This function assumes that the CRC byte was not part of the message.

Parameters

checksum_byte

the CRC8 byte of the received message.

Returns

true if the message checksum is correct.

Definition at line 114 of file Crc.hxx.

get()

uint8_t Crc8DallasMaxim::get ( )

inline

Returns

the checksum of the currently consumed message.

Definition at line 97 of file Crc.hxx.

init()

void Crc8DallasMaxim::init ( )

inline

Re-sets the state machine for checksumming a new message.

Definition at line 91 of file Crc.hxx.

update()

void Crc8DallasMaxim::update ( uint8_t  message_byte )

inline

Processes one byte of the incoming message.

Parameters

message_byte

next byte in the message.

Definition at line 180 of file Crc.hxx.

update0()

void Crc8DallasMaxim::update0 ( uint8_t  message_byte )

inline

Processes one byte of the incoming message.

No lookup table will be used.

Parameters

message_byte

next byte in the message.

Definition at line 122 of file Crc.hxx.

update16()

void Crc8DallasMaxim::update16 ( uint8_t  message_byte )

inline

Processes one byte of the incoming message.

A small lookup table will be used.

Parameters

message_byte

next byte in the message.

Definition at line 164 of file Crc.hxx.

update256()

void Crc8DallasMaxim::update256 ( uint8_t  message_byte )

inline

Processes one byte of the incoming message.

A 256-byte lookup table will be used.

Parameters

message_byte

next byte in the message.

Definition at line 173 of file Crc.hxx.

Member Data Documentation

state_

uint8_t Crc8DallasMaxim::state_

private

Current value of the state register for the CRC computation.

Definition at line 207 of file Crc.hxx.

table256

const uint8_t Crc8DallasMaxim::table256

staticprivate

256-entry lookup table for the update256 function.

Definition at line 225 of file Crc.hxx.

tableHi16

const uint8_t Crc8DallasMaxim::tableHi16

staticprivate

Initial value:

=
{
    0x00, 0x9d, 0x23, 0xbe, 0x46, 0xdb, 0x65, 0xf8,
    0x8c, 0x11, 0xaf, 0x32, 0xca, 0x57, 0xe9, 0x74
}

16-entry lookup table for the update16 function.

Definition at line 269 of file Crc.hxx.

tableLo16

const uint8_t Crc8DallasMaxim::tableLo16

staticprivate

Initial value:

=
{
    0x00, 0x5e, 0xbc, 0xe2, 0x61, 0x3f, 0xdd, 0x83,
    0xc2, 0x9c, 0x7e, 0x20, 0xa3, 0xfd, 0x1f, 0x41,
}

16-entry lookup table for the update16 function.

Definition at line 262 of file Crc.hxx.

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The documentation for this class was generated from the following files:

• Crc.hxx
• Crc.cxx