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31 .Nd test I2C bus and slave devices
40 .Op Fl m Ar tr|ss|rs|no
55 utility can be used to perform raw data transfers (read or write) with devices
57 It can also scan the bus for available devices and reset the I2C controller.
59 The options are as follows:
60 .Bl -tag -width ".Fl d Ar direction"
62 7-bit address on the I2C device to operate on (hex).
64 binary mode - when performing a read operation, the data read from the device
65 is output in binary format on stdout; when doing a write, the binary data to
66 be written to the device is read from stdin.
68 number of bytes to transfer (dec).
70 transfer direction: r - read, w - write.
72 I2C bus to use (default is /dev/iic0).
73 .It Fl m Ar tr|ss|rs|no
74 addressing mode, i.e., I2C bus operations performed after the offset for the
75 transfer has been written to the device and before the actual read/write
77 .Bl -tag -compact -offset indent
87 Some I2C bus hardware does not provide control over the individual start,
88 repeat-start, and stop operations.
89 Such hardware can only perform a complete transfer of the offset and the
90 data as a single operation.
93 mode creates control structures describing the transfer and submits them
94 to the driver as a single complete transaction.
95 This mode works on all types of I2C hardware.
97 skip address - address(es) to be skipped during bus scan.
98 There are two ways to specify addresses to ignore: by range 'a..b' or
99 using selected addresses 'a:b:c'. This option is available only when "-s" is
102 offset within the device for data transfer (hex).
106 to disable writing of the offset to the slave.
108 reset the controller.
110 scan the bus for devices.
114 device addressing width (in bits).
115 This is used to determine how to pass
120 Zero means that the offset is ignored and not passed to the slave at all.
123 Great care must be taken when manipulating slave I2C devices with the
126 Often times important configuration data for the system is kept in non-volatile
127 but write enabled memories located on the I2C bus, for example Ethernet hardware
128 addresses, RAM module parameters (SPD), processor reset configuration word etc.
130 It is very easy to render the whole system unusable when such configuration
131 data is deleted or altered, so use the
133 (write) command only if you know exactly what you are doing.
135 Also avoid ungraceful interrupting of an ongoing transaction on the I2C bus,
136 as it can lead to potentially dangerous effects.
137 Consider the following scenario: when the host CPU is reset (for whatever reason)
138 in the middle of a started I2C transaction, the I2C slave device could be left
139 in write mode waiting for data or offset to arrive.
140 When the CPU reinitializes itself and talks to this I2C slave device again,
141 the commands and other control info it sends are treated by the slave device
142 as data or offset it was waiting for, and there's great potential for
143 corruption if such a write is performed.
147 Scan the default bus (/dev/iic0) for devices:
151 Scan the default bus (/dev/iic0) for devices and skip addresses 0x56 and
156 Scan the default bus (/dev/iic0) for devices and skip address range
161 Read 8 bytes of data from device at address 0x56 (e.g., an EEPROM):
163 i2c -a 0x56 -d r -c 8
165 Write 16 bytes of data from file data.bin to device 0x56 at offset 0x10:
167 i2c -a 0x56 -d w -c 16 -o 0x10 -b < data.bin
169 Copy 4 bytes between two EEPROMs (0x56 on /dev/iic1 to 0x57 on /dev/iic0):
171 i2c -a 0x56 -f /dev/iic1 -d r -c 0x4 -b | i2c -a 0x57 -f /dev/iic0 -d w -c 4 -b
173 Reset the controller:
189 utility and this manual page were written by
190 .An Bartlomiej Sieka Aq Mt tur@semihalf.com
192 .An Michal Hajduk Aq Mt mih@semihalf.com .