Login or Register to Ask a Question and Join Our Community

Linux and UNIX Man Pages

Linux & Unix Commands - Search Man Pages

iicbus(4) [linux man page]

IICBUS(4)						   BSD Kernel Interfaces Manual 						 IICBUS(4)

NAME

     iicbus -- I2C bus system

SYNOPSIS

     device iicbus
     device iicbb

     device iic
     device ic
     device iicsmb

DESCRIPTION

     The iicbus system provides a uniform, modular and architecture-independent system for the implementation of drivers to control various I2C
     devices and to utilize different I2C controllers.

I2C
     I2C is an acronym for Inter Integrated Circuit bus.  The I2C bus was developed in the early 1980's by Philips semiconductors.  Its purpose
     was to provide an easy way to connect a CPU to peripheral chips in a TV-set.

     The BUS physically consists of 2 active wires and a ground connection.  The active wires, SDA and SCL, are both bidirectional.  Where SDA is
     the Serial DAta line and SCL is the Serial CLock line.

     Every component hooked up to the bus has its own unique address whether it is a CPU, LCD driver, memory, or complex function chip.  Each of
     these chips can act as a receiver and/or transmitter depending on its functionality.  Obviously an LCD driver is only a receiver, while a
     memory or I/O chip can both be transmitter and receiver.  Furthermore there may be one or more BUS MASTERs.

     The BUS MASTER is the chip issuing the commands on the BUS.  In the I2C protocol specification it is stated that the IC that initiates a data
     transfer on the bus is considered the BUS MASTER.	At that time all the others are regarded to as the BUS SLAVEs.	As mentioned before, the
     IC bus is a Multi-MASTER BUS.  This means that more than one IC capable of initiating data transfer can be connected to it.

DEVICES

     Some I2C device drivers are available:

     Devices	       Description
     iic	       general i/o operation
     ic 	       network IP interface
     iicsmb	       I2C to SMB software bridge

INTERFACES

     The I2C protocol may be implemented by hardware or software.  Software interfaces rely on very simple hardware, usually two lines twiddled by
     2 registers.  Hardware interfaces are more intelligent and receive 8-bit characters they write to the bus according to the I2C protocol.

     I2C interfaces may act on the bus as slave devices, allowing spontaneous bidirectional communications, thanks to the multi-master capabili-
     ties of the I2C protocol.

     Some I2C interfaces are available:

     Interface		  Description
     pcf		  Philips PCF8584 master/slave interface
     iicbb		  generic bit-banging master-only driver
     lpbb		  parallel port specific bit-banging interface
     bktr		  Brooktree848 video chipset, hardware and software master-only interface

SEE ALSO

     iicbb(4), lpbb(4), pcf(4)

HISTORY

     The iicbus manual page first appeared in FreeBSD 3.0.

AUTHORS

     This manual page was written by Nicolas Souchu.

BSD
								  August 6, 1998							       BSD

Check Out this Related Man Page

I2CGET(8)						      System Manager's Manual							 I2CGET(8)

NAME

       i2cget - read from I2C/SMBus chip registers

SYNOPSIS

       i2cget [-f] [-y] i2cbus chip-address [data-address [mode]]
       i2cget -V

DESCRIPTION

       i2cget is a small helper program to read registers visible through the I2C bus (or SMBus).

OPTIONS

       -V     Display the version and exit.

       -f     Force  access to the device even if it is already busy. By default, i2cget will refuse to access a device which is already under the
	      control of a kernel driver. Using this flag is dangerous, it can seriously confuse the kernel driver in question. It can also  cause
	      i2cget to return an invalid value. So use at your own risk and only if you know what you're doing.

       -y     Disable  interactive  mode. By default, i2cget will wait for a confirmation from the user before messing with the I2C bus. When this
	      flag is used, it will perform the operation directly. This is mainly meant to be used in scripts. Use with caution.

       There are two required options to i2cget. i2cbus indicates the number or name of the I2C bus to be scanned.  This number should	correspond
       to one of the busses listed by i2cdetect -l. chip-address specifies the address of the chip on that bus, and is an integer between 0x03 and
       0x77.

       data-address specifies the address on that chip to read from, and is an integer between 0x00 and 0xFF. If  omitted,  the  currently  active
       register will be read (if that makes sense for the considered chip).

       The mode parameter, if specified, is one of the letters b, w or c, corresponding to a read byte data, a read word data or a write byte/read
       byte transaction, respectively. A p can also be appended to the mode parameter to enable PEC. If the  mode  parameter  is  omitted,  i2cget
       defaults  to a read byte data transaction, unless data-address is also omitted, in which case the default (and only valid) transaction is a
       single read byte.

WARNING

       i2cget can be extremely dangerous if used improperly. I2C and SMBus are designed in such a way that an SMBus read transaction can  be  seen
       as  a  write  transaction  by  certain chips. This is particularly true if setting mode to cp (write byte/read byte with PEC). Be extremely
       careful using this program.

SEE ALSO

       i2cdump(8), i2cset(8)

AUTHOR

       Jean Delvare

       This manual page was strongly inspired from those written by David Z Maze for i2cset.

								     May 2008								 I2CGET(8)
Man Page