i2c man page on FreeBSD

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I2C(8)			  BSD System Manager's Manual			I2C(8)

     i2c — test I2C bus and slave devices

     i2c -a address [-f device] [-d r|w] [-w 0|8|16] [-o offset] [-c count]
	 [-m ss|rs|no] [-b] [-v]
     i2c -s [-f device] [-n skip_addr] [-v]
     i2c -r [-f device] [-v]

     The i2c utility can be used to perform raw data transfers (read or write)
     with devices on the I2C bus. It can also scan the bus for available
     devices and reset the I2C controller.

     The options are as follows:

     -a address	   7-bit address on the I2C device to operate on (hex).

     -b		   binary mode - when performing a read operation, the data
		   read from the device is output in binary format on stdout;
		   when doing a write, the binary data to be written to the
		   device is read from stdin.

     -c count	   number of bytes to transfer (dec).

     -d r|w	   transfer direction: r - read, w - write.

     -f device	   I2C bus to use (default is /dev/iic0).

     -m ss|rs|no   addressing mode, i.e., I2C bus operations performed after
		   the offset for the transfer has been written to the device
		   and before the actual read/write operation. rs - repeated
		   start; ss - stop start; no - none.

     -n skip_addr  skip address - address(es) to be skipped during bus scan.
		   The are two ways to specify addresses to ignore: by range
		   'a..b' or using selected addresses 'a:b:c'. This option is
		   available only when "-s" is used.

     -o offset	   offset within the device for data transfer (hex).

     -r		   reset the controller.

     -s		   scan the bus for devices.

     -v		   be verbose

     -w 0|8|16	   device addressing width (in bits).

     Great care must be taken when manipulating slave I2C devices with the i2c
     utility. Often times important configuration data for the system is kept
     in non-volatile but write enabled memories located on the I2C bus, for
     example Ethernet hardware addresses, RAM module parameters (SPD), proces‐
     sor reset configuration word etc.

     It is very easy to render the whole system unusable when such configura‐
     tion data is deleted or altered, so use the “-d w” (write) command only
     if you know exactly what you are doing.

     Also avoid ungraceful interrupting of an ongoing transaction on the I2C
     bus, as it can lead to potentially dangerous effects. Consider the fol‐
     lowing scenario: when the host CPU is reset (for whatever reason) in the
     middle of a started I2C transaction, the I2C slave device could be left
     in write mode waiting for data or offset to arrive. When the CPU reini‐
     tializes itself and talks to this I2C slave device again, the commands
     and other control info it sends are treated by the slave device as data
     or offset it was waiting for, and there's great potential for corruption
     if such a write is performed.

     ·	 Scan the default bus (/dev/iic0) for devices:

	 i2c -s

     ·	 Scan the default bus (/dev/iic0) for devices and skip addresses 0x56
	 and 0x45.

	 i2c -s -n 0x56:0x45

     ·	 Scan the default bus (/dev/iic0) for devices and skip address range
	 0x34 to 0x56.

	 i2c -s -n 0x34..0x56

     ·	 Read 8 bytes of data from device at address 0x56 (e.g., an EEPROM):

	 i2c -a 0x56 -d r -c 8

     ·	 Write 16 bytes of data from file data.bin to device 0x56 at offset

	 i2c -a 0x56 -d w -c 16 -o 0x10 -b < data.bin

     ·	 Copy 4 bytes between two EEPROMs (0x56 on /dev/iic1 to 0x57 on

	 i2c -a 0x56 -f /dev/iic1 -d r -c 0x4 -b | i2c -a 0x57 -f /dev/iic0 -d
	 w -c 4 -b

     ·	 Reset the controller:

	 i2c -f /dev/iic1 -r

     iic(4), iicbus(4)

     The i2c utility appeared in FreeBSD 8.0.

     The i2c utility and this manual page were written by Bartlomiej Sieka
     ⟨tur@semihalf.com⟩ and Michal Hajduk ⟨mih@semihalf.com⟩.

BSD				 Jan 23, 2009				   BSD

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