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authorMichael Hennerich <michael.hennerich@analog.com>2009-12-14 18:00:15 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2009-12-15 08:53:25 -0800
commit4eb174bee6f8623fed1af0072f1bebfc3b513a52 (patch)
tree9357e122a1fc99a881a0091623acc8fe8ce22112 /Documentation/misc-devices
parent00b55864bb37200d7f05143c44f5e2edfc8c4578 (diff)
downloadkernel-4eb174bee6f8623fed1af0072f1bebfc3b513a52.tar.gz
ad525x_dpot: new driver for AD525x digital potentiometers
This driver supports the non-volatile digital potentiometers via I2C: AD5258, AD5259, AD5251, AD5252, AD5253, AD5254, and AD5255 It provides a sysfs interface to each device for reading/writing which is documented in Documentation/misc-devices/ad525x_dpot.txt. Signed-off-by: Michael Hennerich <michael.hennerich@analog.com> Signed-off-by: Chris Verges <chrisv@cyberswitching.com> Signed-off-by: Mike Frysinger <vapier@gentoo.org> Cc: Jean Delvare <khali@linux-fr.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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+---------------------------------
+ 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