1.. SPDX-License-Identifier: GPL-2.0 2 3============================= 4AD525x Digital Potentiometers 5============================= 6 7The ad525x_dpot driver exports a simple sysfs interface. This allows you to 8work with the immediate resistance settings as well as update the saved startup 9settings. Access to the factory programmed tolerance is also provided, but 10interpretation of this settings is required by the end application according to 11the specific part in use. 12 13Files 14===== 15 16Each dpot device will have a set of eeprom, rdac, and tolerance files. How 17many depends on the actual part you have, as will the range of allowed values. 18 19The eeprom files are used to program the startup value of the device. 20 21The rdac files are used to program the immediate value of the device. 22 23The tolerance files are the read-only factory programmed tolerance settings 24and may vary greatly on a part-by-part basis. For exact interpretation of 25this field, please consult the datasheet for your part. This is presented 26as a hex file for easier parsing. 27 28Example 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 58