i2cset - set I2C registers
i2cset [-f] [-y] [-m mask] [-r] i2cbus chip-address data-address [value
i2cset is a small helper program to set registers visible through the
-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.
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 omited, 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.
The mode parameter, if specified, is one of the letters b or w,
corresponding to a write size of a single byte or a 16-bit word,
respectively. 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 bytes, 0x0000-0xFFFF for words).
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.
Frodo Looijaard, Mark D. Studebaker and Jean Delvare
This manual page was originally written by David Z Maze
<firstname.lastname@example.org> for the Debian GNU/Linux system.