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1Kernel driver pca9539
2=====================
3
4NOTE: this driver is deprecated and will be dropped soon, use
5drivers/gpio/pca9539.c instead.
6
7Supported chips:
8 * Philips PCA9539
9 Prefix: 'pca9539'
10 Addresses scanned: none
11 Datasheet:
12 http://www.semiconductors.philips.com/acrobat/datasheets/PCA9539_2.pdf
13
14Author: Ben Gardner <bgardner@wabtec.com>
15
16
17Description
18-----------
19
20The Philips PCA9539 is a 16 bit low power I/O device.
21All 16 lines can be individually configured as an input or output.
22The input sense can also be inverted.
23The 16 lines are split between two bytes.
24
25
26Detection
27---------
28
29The PCA9539 is difficult to detect and not commonly found in PC machines,
30so you have to pass the I2C bus and address of the installed PCA9539
31devices explicitly to the driver at load time via the force=... parameter.
32
33
34Sysfs entries
35-------------
36
37Each is a byte that maps to the 8 I/O bits.
38A '0' suffix is for bits 0-7, while '1' is for bits 8-15.
39
40input[01] - read the current value
41output[01] - sets the output value
42direction[01] - direction of each bit: 1=input, 0=output
43invert[01] - toggle the input bit sense
44
45input reads the actual state of the line and is always available.
46The direction defaults to input for all channels.
47
48
49General Remarks
50---------------
51
52Note that each output, direction, and invert entry controls 8 lines.
53You should use the read, modify, write sequence.
54For example. to set output bit 0 of 1.
55 val=$(cat output0)
56 val=$(( $val | 1 ))
57 echo $val > output0
58