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/Documentation/misc-devices/ad525x_dpot.txt

https://gitlab.com/vibisreenivasan/UML
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 1---------------------------------
 2  AD525x Digital Potentiometers
 3---------------------------------
 4
 5The ad525x_dpot driver exports a simple sysfs interface.  This allows you to
 6work with the immediate resistance settings as well as update the saved startup
 7settings.  Access to the factory programmed tolerance is also provided, but
 8interpretation of this settings is required by the end application according to
 9the specific part in use.
10
11---------
12  Files
13---------
14
15Each dpot device will have a set of eeprom, rdac, and tolerance files.  How
16many depends on the actual part you have, as will the range of allowed values.
17
18The eeprom files are used to program the startup value of the device.
19
20The rdac files are used to program the immediate value of the device.
21
22The tolerance files are the read-only factory programmed tolerance settings
23and may vary greatly on a part-by-part basis.  For exact interpretation of
24this field, please consult the datasheet for your part.  This is presented
25as a hex file for easier parsing.
26
27-----------
28  Example
29-----------
30
31Locate the device in your sysfs tree.  This is probably easiest by going into
32the common i2c directory and locating the device by the i2c slave address.
33
34	# ls /sys/bus/i2c/devices/
35	0-0022  0-0027  0-002f
36
37So assuming the device in question is on the first i2c bus and has the slave
38address of 0x2f, we descend (unrelated sysfs entries have been trimmed).
39
40	# ls /sys/bus/i2c/devices/0-002f/
41	eeprom0 rdac0 tolerance0
42
43You can use simple reads/writes to access these files:
44
45	# cd /sys/bus/i2c/devices/0-002f/
46
47	# cat eeprom0
48	0
49	# echo 10 > eeprom0
50	# cat eeprom0
51	10
52
53	# cat rdac0
54	5
55	# echo 3 > rdac0
56	# cat rdac0
57	3