NAME

       i2cset - set I2C registers

SYNOPSIS

       i2cset [-f] [-y] [-m mask] [-r] [-a] 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.

       -a     Allow using addresses between 0x00 - 0x07 and 0x78 - 0x7f. Not recommended.

       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
       0x08  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.

EXAMPLES

       Write value 0x42 to 8-bit register 0x11 of the I2C device at 7-bit address 0x2d on  bus  1
       (i2c-1), after user confirmation:
              # i2cset 1 0x2d 0x11 0x42

       Immediately clear the 3 least significant bits of 8-bit register 0x11 of the I2C device at
       7-bit address 0x2d on bus 1 (i2c-1) (no user confirmation):
              # i2cset -y -m 0x07 1 0x2d 0x11 0x00

       Write value 0x5000 to 16-bit register 0x02 of the I2C device at 7-bit address 0x48 on  bus
       1 (i2c-1), after user confirmation:
              # i2cset 1 0x48 0x02 0x5000 w

       Also see i2cget(8) for examples of combined usage of i2cset and i2cget.

BUGS

       To  report  bugs  or  send  fixes,  please  write  to  the  Linux I2C mailing list <linux-
       i2c@vger.kernel.org> with Cc to the current maintainer: Jean Delvare <jdelvare@suse.de>.

SEE ALSO

       i2cdetect(8), i2cdump(8), i2cget(8), i2ctransfer(8), isaset(8)

AUTHOR

       Frodo Looijaard, Mark D. Studebaker and Jean Delvare

       This manual page was originally written by David Z Maze <dmaze@debian.org> for the  Debian
       GNU/Linux system.

                                           October 2017                                 I2CSET(8)