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