com.embeddedunveiled.serial

Class SerialComCRCUtil

java.lang.Object

com.embeddedunveiled.serial.SerialComCRCUtil

public final class SerialComCRCUtil
extends Object

Utility class to calculate and generate CRC values for a given message. This can be used in X/Y/Z modem etc protocol implementations and in developing custom protocols for transmitting data over serial port.

Author:

Rishi Gupta

Constructor Summary

Constructors

Constructor and Description
SerialComCRCUtil() Allocates a new SerialComCRCUtil object.

Method Summary

Methods

Modifier and Type	Method and Description
byte	getChecksumValue(byte[] data, int start, int end) Calculates 8 bit checksum value for the data bytes given.
int	getCRC16CCITTValue(byte[] data, int start, int end) Calculates CRC-16-CCITT value for the data bytes given.
int	getCRC16DNPValue(byte[] data, int start, int end) Calculates CRC-16-DNP value for the data bytes given.
int	getCRC16IBMValue(byte[] data, int start, int end) Calculates CRC-16-IBM value for the data bytes given.
int	getCRC16Value(byte[] data, int start, int end) Calculates CRC-16 value for the data bytes given.
int	getCRC8Dallas1WireValue(byte[] data, int start, int end) Calculates CRC-8 Dallas 1-wire value for the data bytes given.
byte	getLRCCheckSum(byte[] data, int offset, int length) Calculates longitudinal redundancy checksum value for the given byte array.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

SerialComCRCUtil

public SerialComCRCUtil()

Allocates a new SerialComCRCUtil object.

Method Detail

getChecksumValue

public byte getChecksumValue(byte[] data,
                    int start,
                    int end)

Calculates 8 bit checksum value for the data bytes given. The data bytes at start and end index are included in calculation. The checksum returned is the sum of all bytes in the data packet modulo 256.

Parameters:

data - byte type buffer for whom checksum is to be calculated.

start - offset in supplied data buffer from where checksum calculation should start.

end - offset in data buffer till which checksum should be calculated.

Returns:

checksum value for the given data bytes packet.

getLRCCheckSum

public byte getLRCCheckSum(byte[] data,
                  int offset,
                  int length)

Calculates longitudinal redundancy checksum value for the given byte array.

Parameters:

data - byte type buffer for whom LRC checksum is to be calculated.

offset - position in supplied data buffer from where LRC calculation should start.

length - position in data buffer till which LRC should be calculated from offset.

Returns:

LRC checksum value for the given byte array.

Throws:

NullPointerException - if data is null.

IndexOutOfBoundsException - if offset is negative, length is negative, or length is greater than data.length - offset.

IllegalArgumentException - if data is not a byte type array.

getCRC8Dallas1WireValue

public int getCRC8Dallas1WireValue(byte[] data,
                          int start,
                          int end)

Calculates CRC-8 Dallas 1-wire value for the data bytes given. The data bytes at start and end index are included in calculation. It uses pre-defined table for speedily calculating CRC8-1-wire value of the given data.

Parameters:

data - byte type buffer for whom CRC is to be calculated.

start - offset in supplied data buffer from where CRC calculation should start.

end - offset in data buffer till which CRC should be calculated.

Returns:

CRC value of specified data bytes.

getCRC16Value

public int getCRC16Value(byte[] data,
                int start,
                int end)

Calculates CRC-16 value for the data bytes given. The data bytes at start and end index are included in calculation. It uses pre-defined table for speedily calculating CRC-16 value of the given data.

Parameters:

data - byte type buffer for whom CRC is to be calculated.

start - offset in supplied data buffer from where CRC calculation should start.

end - offset in data buffer till which CRC should be calculated.

Returns:

CRC value of specified data bytes.

getCRC16CCITTValue

public int getCRC16CCITTValue(byte[] data,
                     int start,
                     int end)

Calculates CRC-16-CCITT value for the data bytes given. The data bytes at start and end index are included in calculation. It uses pre-defined table for speedily calculating CRC-16-CCITT value of the given data. This algorithm is used in implementing Xmodem protocol.

Parameters:

data - byte type buffer for whom CRC is to be calculated.

start - offset in supplied data buffer from where CRC calculation should start.

end - offset in data buffer till which CRC should be calculated.

Returns:

CRC value of specified data bytes.

getCRC16DNPValue

public int getCRC16DNPValue(byte[] data,
                   int start,
                   int end)

Calculates CRC-16-DNP value for the data bytes given. The data bytes at start and end index are included in calculation. It uses pre-defined table for speedily calculating CRC-16-DNP value of the given data.

Parameters:

data - byte type buffer for whom CRC is to be calculated.

start - offset in supplied data buffer from where CRC calculation should start.

end - offset in data buffer till which CRC should be calculated.

Returns:

CRC value of specified data bytes.

getCRC16IBMValue

public int getCRC16IBMValue(byte[] data,
                   int start,
                   int end)

Calculates CRC-16-IBM value for the data bytes given. The data bytes at start and end index are included in calculation. It uses pre-defined table for speedily calculating CRC-16-IBM (modbus) value of the given data.

Parameters:

data - byte type buffer for whom CRC is to be calculated.

start - offset in supplied data buffer from where CRC calculation should start.

end - offset in data buffer till which CRC should be calculated.

Returns:

CRC value of specified data bytes.