Ubuntu Manpage: i2cset - set I2C registers

NAME

       i2cset - set I2C registers

SYNOPSIS

       i2cset [-f] [-y] [-m mask] [-r] i2cbus chip-address data-address [value] ...  [mode]
       i2cset -V

DESCRIPTION

       i2cset is a small helper program to set registers visible through the I2C bus.

OPTIONS

-V Display the version and exit.

-f Force access to the device even if it is already busy. By default, i2cset 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 i2cset to silently write to the wrong register. So use
at your own risk and only if you know what you're doing.

-y Disable interactive mode. By default, i2cset 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.

-m mask
The mask parameter, if specified, describes which bits of value will be actually
written to data-address. Bits set to 1 in the mask are taken from value, while bits
set to 0 will be read from data-address and thus preserved by the operation. Please
note that this parameter assumes that the read and write operations for the
specified mode are symmetrical for the device you are accessing. This may or may
not be the case, as neither I2C nor SMBus guarantees this.

-r Read back the value right after writing it, and compare the result with the value
written. This used to be the default behavior. The same limitations apply as those
of option -m.

There are three required options to i2cset. 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 write to, and is an
integer between 0x00 and 0xFF.

The value parameter, if specified, is the value to write to that location on the chip. If
this parameter is omitted, then a short write is issued. For most chips, it simply sets an
internal pointer to the target location, but doesn't actually write to that location. For
a few chips though, in particular simple ones with a single register, this short write is
an actual write. If the mode parameter is s or i, multiple values can be specified.

The mode parameter, if specified, is one of the letters b, w, s, or i, corresponding to a
write size of a single byte, a 16-bit word, a SMBus block write, or an I2C block write,
respectively. For SMBus and I2C block writes, the write size is determined by the number
of value parameters. Except for I2C block writes, a p can also be appended to the mode
parameter to enable PEC. If the mode parameter is omitted, i2cset defaults to byte mode
without PEC. The value provided must be within range for the specified data type
(0x00-0xFF for byte and block writes, 0x0000-0xFFFF for words). Another possible mode is
c, which doesn't write any value (so-called short write). You usually don't have to
specify this mode, as it is the default when no value is provided, unless you also want to
enable PEC.

WARNING

       i2cset  can  be extremely dangerous if used improperly. It can confuse your I2C bus, cause
       data loss, or have more serious side effects. Writing to a serial EEPROM on a memory  DIMM
       (chip  addresses  between  0x50  and  0x57)  may  DESTROY your memory, leaving your system
       unbootable!  Be extremely careful using this program.

AUTHOR