1I2CDUMP(8) System Manager's Manual I2CDUMP(8)
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6 i2cdump - examine I2C registers
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10 i2cdump [-f] [-r first-last] [-y] [-a] i2cbus address [mode [bank
11 [bankreg]]]
12 i2cdump -V
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16 i2cdump is a small helper program to examine registers visible through
17 the I2C bus.
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21 -V Display the version and exit.
22 -f Force access to the device even if it is already busy. By de‐
24 fault, i2cdump 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 i2cdump to return invalid results. So use at your
28 own risk and only if you know what you're doing.
29 -r first-last
31 Limit the range of registers being accessed. This option is only
32 available with modes b, w, c and W. For mode W, first must be
33 even and last must be odd.
34 -y Disable interactive mode. By default, i2cdump will wait for a
36 confirmation from the user before messing with the I2C bus. When
37 this flag is used, it will perform the operation directly. This
38 is mainly meant to be used in scripts.
39 -a Allow using addresses between 0x00 - 0x07 and 0x78 - 0x7f. Not
41 recommended.
42 At least two options must be provided to i2cdump. i2cbus indicates the
44 number or name of the I2C bus to be scanned. This number should corre‐
45 spond to one of the busses listed by i2cdetect -l. address indicates
46 the address to be scanned on that bus, and is an integer between 0x08
47 and 0x77.
48 The mode parameter, if specified, is one of the letters b, w, s, or i,
50 corresponding to a read size of a single byte, a 16-bit word, an SMBus
51 block, an I2C block, respectively. The c mode is a little different, it
52 reads all bytes consecutively, and is useful for chips that have an ad‐
53 dress auto-increment feature, such as EEPROMs. The W mode is also spe‐
54 cial, it is similar to w except that a read command will only be issued
55 on even register addresses; this is again mainly useful for EEPROMs.
56 A p can also be appended to the mode parameter (except for i and W) to
58 enable PEC. If the mode parameter is omitted, i2cdump defaults to byte
59 access without PEC.
60 The bank and bankreg parameters are useful on the W83781D and similar
62 chips (at the time of writing, all Winbond and Asus chips). bank is an
63 integer between 0 and 7, and bankreg is an integer between 0x00 and
64 0xFF (default value: 0x4E). The W83781D data sheet has more information
65 on bank selection.
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69 i2cdump can be dangerous if used improperly. Most notably, the c mode
70 starts with WRITING a byte to the chip. On most chips it will be stored
71 in the address pointer register, which is OK, but some chips with a
72 single register or no (visible) register at all will most likely see
73 this as a real WRITE, resulting in possible misbehavior or corruption.
74 Do not use i2cdump on random addresses. Anyway, it is of little use un‐
75 less you have good knowledge of the chip you're working with and an
76 idea of what you are looking for.
77
80 Dump the whole contents of I2C device at 7-bit address 0x50 on bus 9
81 (i2c-9), using the default read method (byte mode), after user confir‐
82 mation:
83 # i2cdump 9 0x50
84 Immediately dump the whole contents of I2C device at 7-bit address 0x50
86 on bus 9 (i2c-9), using I2C block read transactions (no user confirma‐
87 tion):
88 # i2cdump -y 9 0x50 i
89 If the device is an EEPROM, the output would typically be the same as
90 output of the previous example.
91 Dump registers 0x00 to 0x3f of the I2C device at 7-bit address 0x2d on
93 bus 1 (i2c-1), using the default read method (byte mode), after user
94 confirmation:
95 # i2cdump -r 0x00-0x3f 1 0x2d
96 Dump the registers of the SMBus device at address 0x69 on bus 0
98 (i2c-0), using one SMBus block read transaction with error checking en‐
99 abled, after user confirmation:
100 # i2cdump 0 0x69 sp
101
104 To report bugs or send fixes, please write to the Linux I2C mailing
105 list <linux-i2c@vger.kernel.org> with Cc to the current maintainer:
106 Jean Delvare <jdelvare@suse.de>.
107
110 i2cdetect(8), i2cget(8), i2cset(8), i2ctransfer(8), isadump(8)
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114 Frodo Looijaard, Mark D. Studebaker and Jean Delvare
115 This manual page was originally written by David Z Maze <dmaze@de‐
117 bian.org> for the Debian GNU/Linux system.
118 October 2017 I2CDUMP(8)