1I2CDUMP(8) System Manager's Manual I2CDUMP(8)
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6 i2cdump - examine I2C registers
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10 i2cdump [-f] [-y] i2cbus address [mode] [bank [bankreg]]
11 i2cdump -V
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15 i2cdump is a small helper program to examine registers visible through
16 the I2C bus.
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20 -V Display the version and exit.
21 -f Force access to the device even if it is already busy. By
23 default, i2cdump will refuse to access a device which is already
24 under the control of a kernel driver. Using this flag is danger‐
25 ous, it can seriously confuse the kernel driver in question. It
26 can also cause i2cdump to return invalid results. So use at your
27 own risk and only if you know what you're doing.
28 -y Disable interactive mode. By default, i2cdump will wait for a
30 confirmation from the user before messing with the I2C bus. When
31 this flag is used, it will perform the operation directly. This
32 is mainly meant to be used in scripts.
33 At least two options must be provided to i2cdump. i2cbus indicates the
35 number of the I2C bus to be scanned. This number should correspond to
36 one of the busses listed by i2cdetect -l. address indicates the address
37 to be scanned on that bus, and is an integer between 0x00 and 0x7F.
38 The mode parameter, if specified, is one of the letters b, w, s, or i,
40 corresponding to a read size of a single byte, a 16-bit word, an SMBus
41 block, an I2C block, respectively. The c mode is a little different, it
42 reads all bytes consecutively, and is useful for chips that have an
43 address auto-increment feature, such as EEPROMs. The W mode is also
44 special, it is similar to w except that a read command will only be
45 issued on even register addresses; this is again mainly useful for EEP‐
46 ROMs.
47 A p can also be appended to the mode parameter (except for i and W) to
49 enable PEC. If the mode parameter is omitted, i2cdump defaults to byte
50 access without PEC.
51 The bank and bankreg parameters are useful on the W83781D and similar
53 chips (at the time of writing, all Winbond and Asus chips). bank is an
54 integer between 0 and 7, and bankreg is an integer between 0x00 and
55 0xFF (default value: 0x4E). The W83781D data sheet has more information
56 on bank selection.
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60 i2cdump can be dangerous if used improperly. Most notably, the c mode
61 starts with WRITING a byte to the chip. On most chips it will be stored
62 in the address pointer register, which is OK, but some chips with a
63 single register or no (visible) register at all will most likely see
64 this as a real WRITE, resulting in possible misbehavior or corruption.
65 Do not use i2cdump on random addresses. Anyway, it is of little use
66 unless you have an idea of what you are looking for and have some gen‐
67 eral knowledge about hardware monitoring chips internals.
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71 i2cset(8), i2cdetect(8), isadump(8)
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75 Frodo Looijaard, Mark D. Studebaker, and the lm_sensors group
76 http://www.lm-sensors.org/ This manual page was originally written by
77 David Z Maze <dmaze@debian.org> for the Debian GNU/Linux system. It was
78 then reviewed by the lm_sensors team and is now part of the lm_sensors
79 source distribution.
80 June 2007 I2CDUMP(8)