Commit | Line | Data |
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4eb174be MH |
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 |