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Documentation / misc-devices / ad525x_dpot.txt




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Based on kernel version 3.15.4. Page generated on 2014-07-07 09:03 EST.

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