0001 .. SPDX-License-Identifier: GPL-2.0
0002
0003 =============================
0004 AD525x Digital Potentiometers
0005 =============================
0006
0007 The ad525x_dpot driver exports a simple sysfs interface. This allows you to
0008 work with the immediate resistance settings as well as update the saved startup
0009 settings. Access to the factory programmed tolerance is also provided, but
0010 interpretation of this settings is required by the end application according to
0011 the specific part in use.
0012
0013 Files
0014 =====
0015
0016 Each dpot device will have a set of eeprom, rdac, and tolerance files. How
0017 many depends on the actual part you have, as will the range of allowed values.
0018
0019 The eeprom files are used to program the startup value of the device.
0020
0021 The rdac files are used to program the immediate value of the device.
0022
0023 The tolerance files are the read-only factory programmed tolerance settings
0024 and may vary greatly on a part-by-part basis. For exact interpretation of
0025 this field, please consult the datasheet for your part. This is presented
0026 as a hex file for easier parsing.
0027
0028 Example
0029 =======
0030
0031 Locate the device in your sysfs tree. This is probably easiest by going into
0032 the common i2c directory and locating the device by the i2c slave address::
0033
0034 # ls /sys/bus/i2c/devices/
0035 0-0022 0-0027 0-002f
0036
0037 So assuming the device in question is on the first i2c bus and has the slave
0038 address of 0x2f, we descend (unrelated sysfs entries have been trimmed)::
0039
0040 # ls /sys/bus/i2c/devices/0-002f/
0041 eeprom0 rdac0 tolerance0
0042
0043 You can use simple reads/writes to access these files::
0044
0045 # cd /sys/bus/i2c/devices/0-002f/
0046
0047 # cat eeprom0
0048 0
0049 # echo 10 > eeprom0
0050 # cat eeprom0
0051 10
0052
0053 # cat rdac0
0054 5
0055 # echo 3 > rdac0
0056 # cat rdac0
0057 3
