xref: /freebsd/usr.sbin/i2c/i2c.8 (revision 6829dae12bb055451fa467da4589c43bd03b1e64)
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26.\" $FreeBSD$
27.\"
28.Dd January 23, 2009
29.Dt I2C 8
30.Os
31.Sh NAME
32.Nm i2c
33.Nd test I2C bus and slave devices
34.Sh SYNOPSIS
35.Nm
36.Cm -a Ar address
37.Op Fl f Ar device
38.Op Fl d Ar r|w
39.Op Fl w Ar 0|8|16
40.Op Fl o Ar offset
41.Op Fl c Ar count
42.Op Fl m Ar ss|rs|no
43.Op Fl b
44.Op Fl v
45.Nm
46.Cm -s
47.Op Fl f Ar device
48.Op Fl n Ar skip_addr
49.Op Fl v
50.Nm
51.Cm -r
52.Op Fl f Ar device
53.Op Fl v
54.Sh DESCRIPTION
55The
56.Nm
57utility can be used to perform raw data transfers (read or write) with devices
58on the I2C bus. It can also scan the bus for available devices and reset the
59I2C controller.
60.Pp
61The options are as follows:
62.Bl -tag -width ".Fl d Ar direction"
63.It Fl a Ar address
647-bit address on the I2C device to operate on (hex).
65.It Fl b
66binary mode - when performing a read operation, the data read from the device
67is output in binary format on stdout; when doing a write, the binary data to
68be written to the device is read from stdin.
69.It Fl c Ar count
70number of bytes to transfer (dec).
71.It Fl d Ar r|w
72transfer direction: r - read, w - write.
73.It Fl f Ar device
74I2C bus to use (default is /dev/iic0).
75.It Fl m Ar ss|rs|no
76addressing mode, i.e., I2C bus operations performed after the offset for the
77transfer has been written to the device and before the actual read/write
78operation. rs - repeated start; ss - stop start; no - none.
79.It Fl n Ar skip_addr
80skip address - address(es) to be skipped during bus scan.
81There are two ways to specify addresses to ignore: by range 'a..b' or
82using selected addresses 'a:b:c'. This option is available only when "-s" is
83used.
84.It Fl o Ar offset
85offset within the device for data transfer (hex).
86The default is zero.
87Use
88.Dq -w 0
89to disable writing of the offset to the slave.
90.It Fl r
91reset the controller.
92.It Fl s
93scan the bus for devices.
94.It Fl v
95be verbose.
96.It Fl w Ar 0|8|16
97device addressing width (in bits).
98This is used to determine how to pass
99.Ar offset
100specified with
101.Fl o
102to the slave.
103Zero means that the offset is ignored and not passed to the slave at all.
104.El
105.Sh WARNINGS
106Great care must be taken when manipulating slave I2C devices with the
107.Nm
108utility. Often times important configuration data for the system is kept in
109non-volatile but write enabled memories located on the I2C bus, for example
110Ethernet hardware addresses, RAM module parameters (SPD), processor reset
111configuration word etc.
112.Pp
113It is very easy to render the whole system unusable when such configuration
114data is deleted or altered, so use the
115.Dq -d w
116(write) command only if you know exactly what you are doing.
117.Pp
118Also avoid ungraceful interrupting of an ongoing transaction on the I2C bus,
119as it can lead to potentially dangerous effects. Consider the following
120scenario: when the host CPU is reset (for whatever reason) in the middle of a
121started I2C transaction, the I2C slave device could be left in write mode
122waiting for data or offset to arrive. When the CPU reinitializes itself and
123talks to this I2C slave device again, the commands and other control info it
124sends are treated by the slave device as data or offset it was waiting for,
125and there's great potential for corruption if such a write is performed.
126.Sh EXAMPLES
127.Bl -bullet
128.It
129Scan the default bus (/dev/iic0) for devices:
130.Pp
131i2c -s
132.It
133Scan the default bus (/dev/iic0) for devices and skip addresses 0x56 and
1340x45.
135.Pp
136i2c -s -n 0x56:0x45
137.It
138Scan the default bus (/dev/iic0) for devices and skip address range
1390x34 to 0x56.
140.Pp
141i2c -s -n 0x34..0x56
142.It
143Read 8 bytes of data from device at address 0x56 (e.g., an EEPROM):
144.Pp
145i2c -a 0x56 -d r -c 8
146.It
147Write 16 bytes of data from file data.bin to device 0x56 at offset 0x10:
148.Pp
149i2c -a 0x56 -d w -c 16 -o 0x10 -b < data.bin
150.It
151Copy 4 bytes between two EEPROMs (0x56 on /dev/iic1 to 0x57 on /dev/iic0):
152.Pp
153i2c -a 0x56 -f /dev/iic1 -d r -c 0x4 -b | i2c -a 0x57 -f /dev/iic0 -d w -c 4 -b
154.It
155Reset the controller:
156.Pp
157i2c -f /dev/iic1 -r
158.El
159.Sh SEE ALSO
160.Xr iic 4 ,
161.Xr iicbus 4
162.Sh HISTORY
163The
164.Nm
165utility appeared in
166.Fx 8.0 .
167.Sh AUTHORS
168.An -nosplit
169The
170.Nm
171utility and this manual page were written by
172.An Bartlomiej Sieka Aq Mt tur@semihalf.com
173and
174.An Michal Hajduk Aq Mt mih@semihalf.com .
175