From 4eb174bee6f8623fed1af0072f1bebfc3b513a52 Mon Sep 17 00:00:00 2001 From: Michael Hennerich Date: Mon, 14 Dec 2009 18:00:15 -0800 Subject: 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 Signed-off-by: Chris Verges Signed-off-by: Mike Frysinger Cc: Jean Delvare Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/misc-devices/ad525x_dpot.txt | 57 ++++++++++++++++++++++++++++++ 1 file changed, 57 insertions(+) create mode 100644 Documentation/misc-devices/ad525x_dpot.txt (limited to 'Documentation/misc-devices') diff --git a/Documentation/misc-devices/ad525x_dpot.txt b/Documentation/misc-devices/ad525x_dpot.txt new file mode 100644 index 00000000000..0c9413b1cbf --- /dev/null +++ b/Documentation/misc-devices/ad525x_dpot.txt @@ -0,0 +1,57 @@ +--------------------------------- + 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 -- cgit v1.2.3