1 .. SPDX-License-Identifier: GPL-2.0 1 .. SPDX-License-Identifier: GPL-2.0
2 2
3 ============================= 3 =============================
4 AD525x Digital Potentiometers 4 AD525x Digital Potentiometers
5 ============================= 5 =============================
6 6
7 The ad525x_dpot driver exports a simple sysfs 7 The ad525x_dpot driver exports a simple sysfs interface. This allows you to
8 work with the immediate resistance settings as 8 work with the immediate resistance settings as well as update the saved startup
9 settings. Access to the factory programmed to 9 settings. Access to the factory programmed tolerance is also provided, but
10 interpretation of this settings is required by 10 interpretation of this settings is required by the end application according to
11 the specific part in use. 11 the specific part in use.
12 12
13 Files 13 Files
14 ===== 14 =====
15 15
16 Each dpot device will have a set of eeprom, rd 16 Each dpot device will have a set of eeprom, rdac, and tolerance files. How
17 many depends on the actual part you have, as w 17 many depends on the actual part you have, as will the range of allowed values.
18 18
19 The eeprom files are used to program the start 19 The eeprom files are used to program the startup value of the device.
20 20
21 The rdac files are used to program the immedia 21 The rdac files are used to program the immediate value of the device.
22 22
23 The tolerance files are the read-only factory 23 The tolerance files are the read-only factory programmed tolerance settings
24 and may vary greatly on a part-by-part basis. 24 and may vary greatly on a part-by-part basis. For exact interpretation of
25 this field, please consult the datasheet for y 25 this field, please consult the datasheet for your part. This is presented
26 as a hex file for easier parsing. 26 as a hex file for easier parsing.
27 27
28 Example 28 Example
29 ======= 29 =======
30 30
31 Locate the device in your sysfs tree. This is 31 Locate the device in your sysfs tree. This is probably easiest by going into
32 the common i2c directory and locating the devi 32 the common i2c directory and locating the device by the i2c slave address::
33 33
34 # ls /sys/bus/i2c/devices/ 34 # ls /sys/bus/i2c/devices/
35 0-0022 0-0027 0-002f 35 0-0022 0-0027 0-002f
36 36
37 So assuming the device in question is on the f 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 e 38 address of 0x2f, we descend (unrelated sysfs entries have been trimmed)::
39 39
40 # ls /sys/bus/i2c/devices/0-002f/ 40 # ls /sys/bus/i2c/devices/0-002f/
41 eeprom0 rdac0 tolerance0 41 eeprom0 rdac0 tolerance0
42 42
43 You can use simple reads/writes to access thes 43 You can use simple reads/writes to access these files::
44 44
45 # cd /sys/bus/i2c/devices/0-002f/ 45 # cd /sys/bus/i2c/devices/0-002f/
46 46
47 # cat eeprom0 47 # cat eeprom0
48 0 48 0
49 # echo 10 > eeprom0 49 # echo 10 > eeprom0
50 # cat eeprom0 50 # cat eeprom0
51 10 51 10
52 52
53 # cat rdac0 53 # cat rdac0
54 5 54 5
55 # echo 3 > rdac0 55 # echo 3 > rdac0
56 # cat rdac0 56 # cat rdac0
57 3 57 3
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