1I2CSET(8)                   System Manager's Manual                  I2CSET(8)
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NAME

6       i2cset - set I2C registers
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SYNOPSIS

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

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

21       -V     Display the version and exit.
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23       -f     Force  access  to  the  device  even  if  it is already busy. By
24              default, i2cset will refuse to access a device which is  already
25              under the control of a kernel driver. Using this flag is danger‐
26              ous, it can seriously confuse the kernel driver in question.  It
27              can  also  cause i2cset to silently write to the wrong register.
28              So use at your own risk and only if you know what you're doing.
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30       -y     Disable interactive mode. By default, i2cset  will  wait  for  a
31              confirmation from the user before messing with the I2C bus. When
32              this flag is used, it will perform the operation directly.  This
33              is mainly meant to be used in scripts.
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35       -m mask
36              The  mask parameter, if specified, describes which bits of value
37              will be actually written to data-address. Bits set to 1  in  the
38              mask are taken from value, while bits set to 0 will be read from
39              data-address and thus preserved by the  operation.  Please  note
40              that  this  parameter assumes that the read and write operations
41              for the specified mode are symmetrical for the  device  you  are
42              accessing.  This  may or may not be the case, as neither I2C nor
43              SMBus guarantees this.
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45       -r     Read back the value right after  writing  it,  and  compare  the
46              result  with  the  value  written.  This  used to be the default
47              behavior. The same limitations apply as those of option -m.
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49       There are three required options to i2cset. i2cbus indicates the number
50       or name of the I2C bus to be scanned.  This number should correspond to
51       one of the busses listed by i2cdetect -l.  chip-address  specifies  the
52       address  of  the  chip  on that bus, and is an integer between 0x03 and
53       0x77.  data-address specifies the address on that chip to write to, and
54       is an integer between 0x00 and 0xFF.
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56       The  value parameter, if specified, is the value to write to that loca‐
57       tion on the chip. If this parameter is omitted, then a short  write  is
58       issued.  For most chips, it simply sets an internal pointer to the tar‐
59       get location, but doesn't actually write to that location.  For  a  few
60       chips  though,  in  particular simple ones with a single register, this
61       short write is an actual write. If the mode parameter is s or i, multi‐
62       ple values can be specified.
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64       The  mode parameter, if specified, is one of the letters b, w, s, or i,
65       corresponding to a write size of a single byte, a 16-bit word, a  SMBus
66       block  write,  or  an I2C block write, respectively.  For SMBus and I2C
67       block writes, the write size is  determined  by  the  number  of  value
68       parameters.   Except  for I2C block writes, a p can also be appended to
69       the mode parameter to enable PEC.  If the mode  parameter  is  omitted,
70       i2cset  defaults  to  byte mode without PEC. The value provided must be
71       within range for the specified data type (0x00-0xFF for byte and  block
72       writes,  0x0000-0xFFFF  for  words).  Another possible mode is c, which
73       doesn't write any value (so-called short write). You usually don't have
74       to  specify  this mode, as it is the default when no value is provided,
75       unless you also want to enable PEC.
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WARNING

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

87       i2cdump(8), isaset(8)
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AUTHOR

91       Frodo Looijaard, Mark D. Studebaker and Jean Delvare
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93       This  manual  page   was   originally   written   by   David   Z   Maze
94       <dmaze@debian.org> for the Debian GNU/Linux system.
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98                                 November 2008                       I2CSET(8)
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