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