com.pi4j.jni

Class I2C

java.lang.Object

com.pi4j.jni.I2C

public class I2C
extends Object

I2C Communication

Set of native methods for interacting with i2c bus on RPi.

Note: The file descriptor (fd) returned is a standard Linux filehandle. You can use the standard read(), write(), etc. system calls on this filehandle as required.

Author:

Daniel Sendula

Method Summary

Modifier and Type	Method and Description
static int	i2cClose(int fd) Closes linux file.
static int	i2cOpen(String device) Opens linux file for r/w returning file handle.
static int	i2cReadByte(int fd, int deviceAddress, int localAddress) Reads one byte from i2c device.
static int	i2cReadByteDirect(int fd, int deviceAddress) Reads one byte from i2c device.
static int	i2cReadBytes(int fd, int deviceAddress, int localAddress, int size, int offset, byte[] buffer) Reads more bytes from i2c device.
static int	i2cReadBytesDirect(int fd, int deviceAddress, int size, int offset, byte[] buffer) Reads more bytes from i2c device.
static int	i2cWriteAndReadBytes(int fd, int deviceAddress, int writeSize, int writeOffset, byte[] writeBuffer, int readSize, int readOffset, byte[] readBuffer) Reads more bytes from i2c device.
static int	i2cWriteByte(int fd, int deviceAddress, int localAddress, byte data) Writes one byte to i2c.
static int	i2cWriteByteDirect(int fd, int deviceAddress, byte data) Writes one byte to i2c.
static int	i2cWriteBytes(int fd, int deviceAddress, int localAddress, int size, int offset, byte[] buffer) Writes several bytes to i2c.
static int	i2cWriteBytesDirect(int fd, int deviceAddress, int size, int offset, byte[] buffer) Writes several bytes to i2c.

Methods inherited from class java.lang.Object

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

Method Detail

i2cOpen

public static int i2cOpen(String device)

Opens linux file for r/w returning file handle.

Parameters:

device - file name of device. For i2c should be /dev/i2c-0 or /dev/i2c-1 for first or second bus.

Returns:

file descriptor or i2c bus.

i2cClose

public static int i2cClose(int fd)

Closes linux file.

Parameters:

fd - file descriptor

i2cWriteByteDirect

public static int i2cWriteByteDirect(int fd,
                                     int deviceAddress,
                                     byte data)

Writes one byte to i2c. It uses ioctl to define device address and then writes one byte.

Parameters:

fd - file descriptor of i2c bus

deviceAddress - device address

data - byte to be written to the device

Returns:

result of operation. Zero if everything is OK, less than zero if there was an error.

i2cWriteBytesDirect

public static int i2cWriteBytesDirect(int fd,
                                      int deviceAddress,
                                      int size,
                                      int offset,
                                      byte[] buffer)

Writes several bytes to i2c. It uses ioctl to define device address and then writes number of bytes defined in size argument.

Parameters:

fd - file descriptor of i2c bus

deviceAddress - device address

size - number of bytes to be written

offset - offset in buffer to read from

buffer - data buffer to be written

Returns:

result of operation. Zero if everything is OK, less than zero if there was an error.

i2cWriteByte

public static int i2cWriteByte(int fd,
                               int deviceAddress,
                               int localAddress,
                               byte data)

Writes one byte to i2c. It uses ioctl to define device address and then writes two bytes: address in the device itself and value.

Parameters:

fd - file descriptor of i2c bus

deviceAddress - device address

localAddress - address in the device

data - byte to be written to the device

Returns:

result of operation. Zero if everything is OK, less than zero if there was an error.

i2cWriteBytes

public static int i2cWriteBytes(int fd,
                                int deviceAddress,
                                int localAddress,
                                int size,
                                int offset,
                                byte[] buffer)

Writes several bytes to i2c. It uses ioctl to define device address and then writes number of bytes defined in size argument plus one.

Parameters:

fd - file descriptor of i2c bus

deviceAddress - device address

localAddress - address in the device

size - number of bytes to be written

offset - offset in buffer to read from

buffer - data buffer to be written

Returns:

result of operation. Zero if everything is OK, less than zero if there was an error.

i2cReadByteDirect

public static int i2cReadByteDirect(int fd,
                                    int deviceAddress)

Reads one byte from i2c device. It uses ioctl to define device address and then reads one byte.

Parameters:

fd - file descriptor of i2c bus

deviceAddress - device address

Returns:

positive number (or zero) to 255 if read was successful. Negative number if reading failed.

i2cReadBytesDirect

public static int i2cReadBytesDirect(int fd,
                                     int deviceAddress,
                                     int size,
                                     int offset,
                                     byte[] buffer)

Reads more bytes from i2c device. It uses ioctl to define device address and then reads size number of bytes.

Parameters:

fd - file descriptor of i2c bus

deviceAddress - device address

size - number of bytes to be read

offset - offset in buffer to stored read data

buffer - buffer for data to be written to

Returns:

number of bytes read or negative number if reading failed.

i2cReadByte

public static int i2cReadByte(int fd,
                              int deviceAddress,
                              int localAddress)

Reads one byte from i2c device. It uses ioctl to define device address, writes addres in device and then reads one byte.

Parameters:

fd - file descriptor of i2c bus

deviceAddress - device address

localAddress - address in the device

Returns:

positive number (or zero) to 255 if read was successful. Negative number if reading failed.

i2cReadBytes

public static int i2cReadBytes(int fd,
                               int deviceAddress,
                               int localAddress,
                               int size,
                               int offset,
                               byte[] buffer)

Reads more bytes from i2c device. It uses ioctl to define device address, writes addres in device and then reads size number of bytes.

Parameters:

fd - file descriptor of i2c bus

deviceAddress - device address

localAddress - address in the device

size - number of bytes to be read

offset - offset in buffer to stored read data

buffer - buffer for data to be written to

Returns:

number of bytes read or negative number if reading failed.

i2cWriteAndReadBytes

public static int i2cWriteAndReadBytes(int fd,
                                       int deviceAddress,
                                       int writeSize,
                                       int writeOffset,
                                       byte[] writeBuffer,
                                       int readSize,
                                       int readOffset,
                                       byte[] readBuffer)

Reads more bytes from i2c device. It uses ioctl to define device address, writes addres in device and then reads size number of bytes.

Parameters:

fd - file descriptor of i2c bus

deviceAddress - device address

writeSize - number of bytes to write

writeOffset - offset in write buffer to start write data

writeBuffer - buffer for data to be written from

readSize - number of bytes to be read

readOffset - offset in read buffer to stored read data

readBuffer - buffer for data read to be stored in

Returns:

number of bytes read or negative number if reading failed.