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Kernel driver pca9539
=====================
Supported chips:
* Philips PCA9539
Prefix: 'pca9539'
Addresses scanned: 0x74 - 0x77
Datasheet:
http://www.semiconductors.philips.com/acrobat/datasheets/PCA9539_2.pdf
Author: Ben Gardner <bgardner@wabtec.com>
Description
-----------
The Philips PCA9539 is a 16 bit low power I/O device.
All 16 lines can be individually configured as an input or output.
The input sense can also be inverted.
The 16 lines are split between two bytes.
Sysfs entries
-------------
Each is a byte that maps to the 8 I/O bits.
A '0' suffix is for bits 0-7, while '1' is for bits 8-15.
input[01] - read the current value
output[01] - sets the output value
direction[01] - direction of each bit: 1=input, 0=output
invert[01] - toggle the input bit sense
input reads the actual state of the line and is always available.
The direction defaults to input for all channels.
General Remarks
---------------
Note that each output, direction, and invert entry controls 8 lines.
You should use the read, modify, write sequence.
For example. to set output bit 0 of 1.
val=$(cat output0)
val=$(( $val | 1 ))
echo $val > output0
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