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

NAME
     i2c - test I2C bus and slave devices

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

DESCRIPTION
     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 tr|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.
                               tr      complete-transfer
                               ss      stop then start
                               rs      repeated start
                               no      none
                         Some I2C bus hardware does not provide control over
                         the individual start, repeat-start, and stop
                         operations.  Such hardware can only perform a
                         complete transfer of the offset and the data as a
                         single operation.  The tr mode creates control
                         structures describing the transfer and submits them
                         to the driver as a single complete transaction.  This
                         mode works on all types of I2C hardware.

     -n skip_addr        skip address - address(es) to be skipped during bus
                         scan.  There 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).
                         The default is zero.  Use "-w 0" to disable writing
                         of the offset to the slave.

     -r                  reset the controller.

     -s                  scan the bus for devices.

     -v                  be verbose.

     -w 0|8|16           device addressing width (in bits).  This is used to
                         determine how to pass offset specified with -o to the
                         slave.  Zero means that the offset is ignored and not
                         passed to the slave at all.

WARNINGS
     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),
     processor reset configuration word etc.

     It is very easy to render the whole system unusable when such
     configuration 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
     following 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
     reinitializes 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.

EXAMPLES
     •   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
         0x10:

         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
         /dev/iic0):

         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

SEE ALSO
     iic(4), iicbus(4)

HISTORY
     The i2c utility appeared in FreeBSD 8.0.

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

FreeBSD 13.1-RELEASE-p6          May 22, 2019          FreeBSD 13.1-RELEASE-p6