jcontrol.comm
Class I2C

java.lang.Object
  jcontrol.comm.I2C

All Implemented Interfaces:

BasicInputStream, BasicOutputStream

public class I2C
extends Object
implements BasicInputStream, BasicOutputStream

Controls I²C devices connected to JControl. The I²C bus is a de facto standard for on board inter integrated circuit communication invented by Phillips (NXP). Many chips are supporting this bus, including the JControl RTC on some Boards.

Currently JControl only works as I²C busmaster, so it can only send data and send requests for data actively. It can't poll the bus as slave and reply for requests of other masters. It is a simple hardware layer implementation so any bus error and any lost arbitration results in an IOException after some retries. To avoid blocking there is contrary to the specification a bus timeout also resulting in an IOException.

Another bus system based on I²C is the SM (system management) bus available on some PC motherboards, for monitoring tempeartures and controlling fans.

Field Summary

static int	MODE_10BIT Selects I2C mode with 10-bit addresses.
static int	MODE_7BIT Selects I2C mode with 7-bit addresses (default).

Constructor Summary

I2C(int address)
Constructs a new I²C object for 7-bit addresseing.

I2C(int address, int mode)
Constructs a new I²C object.

Method Summary

int	available() Note: not supported
void	close() Closes this I2C instance, further reads or writes are not possible.
void	flush() Note: not supported
void	mark(int readlimit) Note: not supported
boolean	markSupported() Note: not supported, always returning false
int	read() Just reads a single byte from the I2C device.
int	read(byte[] data) Reads a data stream from a I2C device.
int	read(byte[] cmd, byte[] data, int startindex, int length) Writes a command stream to a I2C device and reads a reply in the same transaction.
int	read(byte[] data, int startindex, int length) Reads a data stream from a I2C device.
void	reset() Note: not supported
int	skip(int n) Note: not supported
void	write(byte[] data) Writes a data stream to a I2C device.
void	write(byte[] cmd, byte[] data, int startindex, int length) Writes a command stream and a data stream to a I2C device in the same transaction.
void	write(byte[] data, int startindex, int length) Writes a data stream to a I2C device.
void	write(int data) Just writes a single byte to the I2C device.

Methods inherited from class java.lang.Object

clone, equals, getClass, notifyAll, toString, wait

Field Detail

MODE_7BIT

public static final int MODE_7BIT

Selects I²C mode with 7-bit addresses (default).

See Also:

Constant Field Values

MODE_10BIT

public static final int MODE_10BIT

Selects I²C mode with 10-bit addresses. (Note: not all I²C devices support the 10-bit addressing mode, refer the data sheet.)

See Also:

Constant Field Values

Constructor Detail

I2C

public I2C(int address)

Constructs a new I²C object for 7-bit addresseing.

Parameters:

address - 7-bit address of the the device to send data to

I2C

public I2C(int address,
           int mode)

Constructs a new I²C object.

Parameters:

address - of the the device to send data to

mode - bus mode (addressing etc)

See Also:

MODE_7BIT, MODE_10BIT

Method Detail

write

public void write(byte[] data,
                  int startindex,
                  int length)
           throws IOException

Writes a data stream to a I²C device. This method blocks until the transaction is complete or aborted with an error.

Specified by:

write in interface BasicOutputStream

Parameters:

data - the buffer that holds the data to write

startindex - the index to start reading the array (and writing to I²C)

length - number of bytes to write; the array is read from startindex to startindex+length-1

Throws:

IOException - if an error occurs

read

public int read(byte[] data,
                int startindex,
                int length)
         throws IOException

Reads a data stream from a I²C device. This method blocks until the transaction is complete or aborted with an error.

Specified by:

read in interface BasicInputStream

Parameters:

data - the buffer to fill

startindex - the index to start filling the array (with data read from I²C)

length - number of bytes to read; the array is filled from startindex to startindex+length-1, it may be partially filled according to the I²C slave device

Returns:

the number of received bytes

Throws:

IOException - if an error occurs

See Also:

InputStream.read()

write

public void write(byte[] data)
           throws IOException

Writes a data stream to a I²C device. This method blocks until the transaction is complete or aborted with an error.

Specified by:

write in interface BasicOutputStream

Parameters:

data - the buffer that holds the data to write

Throws:

IOException - if an error occurs

See Also:

OutputStream.write(byte[], int, int)

read

public int read(byte[] data)
         throws IOException

Reads a data stream from a I²C device. This method blocks until the transaction is complete or aborted with an error.

Specified by:

read in interface BasicInputStream

Parameters:

data - the buffer to fill

Returns:

the number of received bytes

Throws:

IOException - if an error occurs

See Also:

InputStream.read(byte[], int, int)

write

public void write(byte[] cmd,
                  byte[] data,
                  int startindex,
                  int length)
           throws IOException

Writes a command stream and a data stream to a I²C device in the same transaction. This is an often used sequence for I²C devices that support multiple registers, so a command byte (=register address) is sent and then the register is written. This method is recommended for multi master systems. This method blocks until the transaction is complete or aborted with an error.

Parameters:

cmd - the buffer with command to write (all bytes of array, null for command omission)

data - the buffer to read data to transmit

startindex - the index to start reading the array (and writing to I²C)

length - number of bytes to read; the array is accessed from startindex to startindex+length-1

Throws:

IOException - if an error occurs

read

public int read(byte[] cmd,
                byte[] data,
                int startindex,
                int length)
         throws IOException

Writes a command stream to a I²C device and reads a reply in the same transaction. This is an often used sequence for I²C devices that support multiple registers, so a command byte (=register address) is sent and then the register is read. This method is recommended for multi master systems. This method blocks until the transaction is complete or aborted with an error.

Parameters:

cmd - the buffer with command to write (all bytes of array, null for command omission)

data - the buffer to write received data

startindex - the index to start writing the array (and reading from to I²C)

length - number of bytes to write; the array is accessed from startindex to startindex+length-1, it may be partially filled according to the I²C slave device

Returns:

the number of received bytes

Throws:

IOException - if an error occurs

close

public void close()

Closes this I²C instance, further reads or writes are not possible.

Specified by:

close in interface BasicInputStream

Specified by:

close in interface BasicOutputStream

See Also:

BasicOutputStream.close()

write

public void write(int data)
           throws IOException

Just writes a single byte to the I²C device.

Specified by:

write in interface BasicOutputStream

Parameters:

data - I2C Data to transmit (range 0...255)

Throws:

IOException - if an I/O error occurs. In particular, an IOException may be thrown if the output stream has been closed.

See Also:

BasicOutputStream#write(char)

read

public int read()
         throws IOException

Just reads a single byte from the I²C device.

Specified by:

read in interface BasicInputStream

Returns:

received I2C Data (range 0...255)

Throws:

IOException - if an I/O error occurs.

See Also:

BasicInputStream.read()

skip

public int skip(int n)
         throws IOException

Note: not supported

Specified by:

skip in interface BasicInputStream

Parameters:

n - the number of bytes to be skipped.

Returns:

the actual number of bytes skipped.

Throws:

IOException - if an I/O error occurs.

available

public int available()
              throws IOException

Note: not supported

Specified by:

available in interface BasicInputStream

Returns:

the number of bytes that can be read from this input stream without blocking.

Throws:

IOException - if an I/O error occurs.

mark

public void mark(int readlimit)

Note: not supported

Specified by:

mark in interface BasicInputStream

Parameters:

readlimit - the maximum limit of bytes that can be read before the mark position becomes invalid.

reset

public void reset()
           throws IOException

Note: not supported

Specified by:

reset in interface BasicInputStream

Throws:

IOException - if this stream has not been makred or if the mark has been invalidated.

markSupported

public boolean markSupported()

Note: not supported, always returning false

Specified by:

markSupported in interface BasicInputStream

Returns:

true if this stream instance supports the mark and reset methods; false otherwise.

flush

public void flush()
           throws IOException

Note: not supported

Specified by:

flush in interface BasicOutputStream

Throws:

IOException - if an I/O error occurs.