mirror of
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2025-11-01 09:13:37 +00:00
8a05eb89cb
- use title markups; - mark literal blocks. Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Link: https://lore.kernel.org/r/1b1f4e5e57fd2065828cecc9d07afbd247349e94.1592203650.git.mchehab+huawei@kernel.org Signed-off-by: Jonathan Corbet <corbet@lwn.net>
57 lines
1.6 KiB
ReStructuredText
57 lines
1.6 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0
|
|
|
|
=============================
|
|
AD525x Digital Potentiometers
|
|
=============================
|
|
|
|
The ad525x_dpot driver exports a simple sysfs interface. This allows you to
|
|
work with the immediate resistance settings as well as update the saved startup
|
|
settings. Access to the factory programmed tolerance is also provided, but
|
|
interpretation of this settings is required by the end application according to
|
|
the specific part in use.
|
|
|
|
Files
|
|
=====
|
|
|
|
Each dpot device will have a set of eeprom, rdac, and tolerance files. How
|
|
many depends on the actual part you have, as will the range of allowed values.
|
|
|
|
The eeprom files are used to program the startup value of the device.
|
|
|
|
The rdac files are used to program the immediate value of the device.
|
|
|
|
The tolerance files are the read-only factory programmed tolerance settings
|
|
and may vary greatly on a part-by-part basis. For exact interpretation of
|
|
this field, please consult the datasheet for your part. This is presented
|
|
as a hex file for easier parsing.
|
|
|
|
Example
|
|
=======
|
|
|
|
Locate the device in your sysfs tree. This is probably easiest by going into
|
|
the common i2c directory and locating the device by the i2c slave address::
|
|
|
|
# ls /sys/bus/i2c/devices/
|
|
0-0022 0-0027 0-002f
|
|
|
|
So assuming the device in question is on the first i2c bus and has the slave
|
|
address of 0x2f, we descend (unrelated sysfs entries have been trimmed)::
|
|
|
|
# ls /sys/bus/i2c/devices/0-002f/
|
|
eeprom0 rdac0 tolerance0
|
|
|
|
You can use simple reads/writes to access these files::
|
|
|
|
# cd /sys/bus/i2c/devices/0-002f/
|
|
|
|
# cat eeprom0
|
|
0
|
|
# echo 10 > eeprom0
|
|
# cat eeprom0
|
|
10
|
|
|
|
# cat rdac0
|
|
5
|
|
# echo 3 > rdac0
|
|
# cat rdac0
|
|
3
|