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1 | .. SPDX-License-Identifier: GPL-2.0 |
2 | ||
3 | ============================= | |
4 | AD525x Digital Potentiometers | |
5 | ============================= | |
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6 | |
7 | The ad525x_dpot driver exports a simple sysfs interface. This allows you to | |
8 | work with the immediate resistance settings as well as update the saved startup | |
9 | settings. Access to the factory programmed tolerance is also provided, but | |
10 | interpretation of this settings is required by the end application according to | |
11 | the specific part in use. | |
12 | ||
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13 | Files |
14 | ===== | |
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15 | |
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 will the range of allowed values. | |
18 | ||
19 | The eeprom files are used to program the startup value of the device. | |
20 | ||
21 | The rdac files are used to program the immediate value of the device. | |
22 | ||
23 | The tolerance files are the read-only factory programmed tolerance settings | |
24 | and may vary greatly on a part-by-part basis. For exact interpretation of | |
25 | this field, please consult the datasheet for your part. This is presented | |
26 | as a hex file for easier parsing. | |
27 | ||
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28 | Example |
29 | ======= | |
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30 | |
31 | Locate the device in your sysfs tree. This is probably easiest by going into | |
8a05eb89 | 32 | the common i2c directory and locating the device by the i2c slave address:: |
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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 | |
8a05eb89 | 38 | address of 0x2f, we descend (unrelated sysfs entries have been trimmed):: |
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39 | |
40 | # ls /sys/bus/i2c/devices/0-002f/ | |
41 | eeprom0 rdac0 tolerance0 | |
42 | ||
8a05eb89 | 43 | You can use simple reads/writes to access these files:: |
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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 |