58 lines
1.6 KiB
ReStructuredText
58 lines
1.6 KiB
ReStructuredText
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.. SPDX-License-Identifier: GPL-2.0
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=============================
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AD525x Digital Potentiometers
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=============================
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The ad525x_dpot driver exports a simple sysfs interface. This allows you to
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work with the immediate resistance settings as well as update the saved startup
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settings. Access to the factory programmed tolerance is also provided, but
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interpretation of this settings is required by the end application according to
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the specific part in use.
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Files
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=====
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Each dpot device will have a set of eeprom, rdac, and tolerance files. How
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many depends on the actual part you have, as will the range of allowed values.
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The eeprom files are used to program the startup value of the device.
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The rdac files are used to program the immediate value of the device.
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The tolerance files are the read-only factory programmed tolerance settings
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and may vary greatly on a part-by-part basis. For exact interpretation of
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this field, please consult the datasheet for your part. This is presented
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as a hex file for easier parsing.
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Example
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=======
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Locate the device in your sysfs tree. This is probably easiest by going into
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the common i2c directory and locating the device by the i2c slave address::
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# ls /sys/bus/i2c/devices/
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0-0022 0-0027 0-002f
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So assuming the device in question is on the first i2c bus and has the slave
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address of 0x2f, we descend (unrelated sysfs entries have been trimmed)::
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# ls /sys/bus/i2c/devices/0-002f/
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eeprom0 rdac0 tolerance0
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You can use simple reads/writes to access these files::
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# cd /sys/bus/i2c/devices/0-002f/
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# cat eeprom0
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0
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# echo 10 > eeprom0
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# cat eeprom0
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10
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# cat rdac0
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5
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# echo 3 > rdac0
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# cat rdac0
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3
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