Package com.pi4j.wiringpi

Class I2C

java.lang.Object

com.pi4j.wiringpi.I2C

public class I2C
extends Object

WiringPi includes a library which can make it easier to use the Raspberry Pi’s on-board I2C interface.

Before you can use the I2C interface, you may need to use the gpio utility to load the I2C drivers into the kernel:

$ gpio load i2c

If you need a baud rate other than the default 100Kbps, then you can supply this on the command-line:

$ gpio load i2c 1000

which will set the baud rate to 1000Kbps – ie. 1,000,000 bps. (K here is times 1000)

This library depends on the wiringPi native system library. (developed by Gordon Henderson @ http://wiringpi.com/)

Author:

Robert Savage (http://www.savagehomeautomation.com)

See Also:

https://www.pi4j.com, http://wiringpi.com/reference/i2c-library

Field Summary

Fields

Modifier and Type	Field	Description
static int	CHANNEL_0
static int	CHANNEL_1

Method Summary

Modifier and Type	Method	Description
static int	wiringPiI2CRead(int fd)	wiringPiI2CRead:
static int	wiringPiI2CReadReg16(int fd, int reg)	wiringPiI2CReadReg16:
static int	wiringPiI2CReadReg8(int fd, int reg)	wiringPiI2CReadReg8:
static int	wiringPiI2CSetup(int devid)	wiringPiI2CSetup:
static int	wiringPiI2CWrite(int fd, int data)	wiringPiI2CWrite:
static int	wiringPiI2CWriteReg16(int fd, int reg, int data)	wiringPiI2CWriteReg16:
static int	wiringPiI2CWriteReg8(int fd, int reg, int data)	wiringPiI2CWriteReg8:

Methods inherited from class java.lang.Object

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

Field Detail

CHANNEL_0

public static int CHANNEL_0

CHANNEL_1

public static int CHANNEL_1

Method Detail

wiringPiI2CSetup

public static int wiringPiI2CSetup(int devid)

wiringPiI2CSetup:

This initialises the I2C system with your given device identifier. The ID is the I2C number of the device and you can use the i2cdetect program to find this out. wiringPiI2CSetup() will work out which revision Raspberry Pi you have and open the appropriate device in /dev.

The return value is the standard Linux filehandle, or -1 if any error – in which case, you can consult errno as usual.

E.g. the popular MCP23017 GPIO expander is usually device Id 0×20, so this is the number you would pass into wiringPiI2CSetup().

Parameters:

devid - I2C device id

Returns:

return -1 on error; else returns Linux file handle

See Also:

http://wiringpi.com/reference/i2c-library

wiringPiI2CRead

public static int wiringPiI2CRead(int fd)

wiringPiI2CRead:

Simple I2C device read. Some devices present data when you read them without having to do any register transactions.

Parameters:

fd - Linux file handle obtained from call to wiringPiI2CSetup

Returns:

return -1 on error; else data read from I2C device

See Also:

http://wiringpi.com/reference/i2c-library

wiringPiI2CWrite

public static int wiringPiI2CWrite(int fd,
                                   int data)

wiringPiI2CWrite:

Simple I2C device write. Some devices accept data this way without needing to access any internal registers.

Parameters:

fd - Linux file handle obtained from call to wiringPiI2CSetup

data - data to write

Returns:

return -1 on error

See Also:

http://wiringpi.com/reference/i2c-library

wiringPiI2CWriteReg8

public static int wiringPiI2CWriteReg8(int fd,
                                       int reg,
                                       int data)

wiringPiI2CWriteReg8:

I2C device write. Write an 8-bit data value into the device register indicated.

Parameters:

fd - Linux file handle obtained from call to wiringPiI2CSetup

reg - I2C device register address

data - data byte to write (8 bits/1 byte)

Returns:

return -1 on error

See Also:

http://wiringpi.com/reference/i2c-library

wiringPiI2CWriteReg16

public static int wiringPiI2CWriteReg16(int fd,
                                        int reg,
                                        int data)

wiringPiI2CWriteReg16:

I2C device write. Write a 16-bit data value into the device register indicated.

Parameters:

fd - Linux file handle obtained from call to wiringPiI2CSetup

reg - I2C device register address

data - data bytes to write (16 bits/2 bytes)

Returns:

return -1 on error

See Also:

http://wiringpi.com/reference/i2c-library

wiringPiI2CReadReg8

public static int wiringPiI2CReadReg8(int fd,
                                      int reg)

wiringPiI2CReadReg8:

I2C device read. Read an 8-bit (1 byte) data value from the device register indicated.

Parameters:

fd - Linux file handle obtained from call to wiringPiI2CSetup

reg - I2C device register address

Returns:

return -1 on error; else returns 8-bit value read from I2C device register

See Also:

http://wiringpi.com/reference/i2c-library

wiringPiI2CReadReg16

public static int wiringPiI2CReadReg16(int fd,
                                       int reg)

wiringPiI2CReadReg16:

I2C device read. Read a 16-bit (2 bytes) data value from the device register indicated.

Parameters:

fd - Linux file handle obtained from call to wiringPiI2CSetup

reg - I2C device register address

Returns:

return -1 on error; else returns 16-bit value read from I2C device register

See Also:

http://wiringpi.com/reference/i2c-library