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diff --git a/Documentation/i2c/chips/pcf8574 b/Documentation/i2c/chips/pcf8574 deleted file mode 100644 index 235815c075ff..000000000000 --- a/Documentation/i2c/chips/pcf8574 +++ /dev/null | |||
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1 | Kernel driver pcf8574 | ||
2 | ===================== | ||
3 | |||
4 | Supported chips: | ||
5 | * Philips PCF8574 | ||
6 | Prefix: 'pcf8574' | ||
7 | Addresses scanned: none | ||
8 | Datasheet: Publicly available at the Philips Semiconductors website | ||
9 | http://www.semiconductors.philips.com/pip/PCF8574P.html | ||
10 | |||
11 | * Philips PCF8574A | ||
12 | Prefix: 'pcf8574a' | ||
13 | Addresses scanned: none | ||
14 | Datasheet: Publicly available at the Philips Semiconductors website | ||
15 | http://www.semiconductors.philips.com/pip/PCF8574P.html | ||
16 | |||
17 | Authors: | ||
18 | Frodo Looijaard <frodol@dds.nl>, | ||
19 | Philip Edelbrock <phil@netroedge.com>, | ||
20 | Dan Eaton <dan.eaton@rocketlogix.com>, | ||
21 | Aurelien Jarno <aurelien@aurel32.net>, | ||
22 | Jean Delvare <khali@linux-fr.org>, | ||
23 | |||
24 | |||
25 | Description | ||
26 | ----------- | ||
27 | The PCF8574(A) is an 8-bit I/O expander for the I2C bus produced by Philips | ||
28 | Semiconductors. It is designed to provide a byte I2C interface to up to 16 | ||
29 | separate devices (8 x PCF8574 and 8 x PCF8574A). | ||
30 | |||
31 | This device consists of a quasi-bidirectional port. Each of the eight I/Os | ||
32 | can be independently used as an input or output. To setup an I/O as an | ||
33 | input, you have to write a 1 to the corresponding output. | ||
34 | |||
35 | For more informations see the datasheet. | ||
36 | |||
37 | |||
38 | Accessing PCF8574(A) via /sys interface | ||
39 | ------------------------------------- | ||
40 | |||
41 | The PCF8574(A) is plainly impossible to detect ! Stupid chip. | ||
42 | So, you have to pass the I2C bus and address of the installed PCF857A | ||
43 | and PCF8574A devices explicitly to the driver at load time via the | ||
44 | force=... parameter. | ||
45 | |||
46 | On detection (i.e. insmod, modprobe et al.), directories are being | ||
47 | created for each detected PCF8574(A): | ||
48 | |||
49 | /sys/bus/i2c/devices/<0>-<1>/ | ||
50 | where <0> is the bus the chip was detected on (e. g. i2c-0) | ||
51 | and <1> the chip address ([20..27] or [38..3f]): | ||
52 | |||
53 | (example: /sys/bus/i2c/devices/1-0020/) | ||
54 | |||
55 | Inside these directories, there are two files each: | ||
56 | read and write (and one file with chip name). | ||
57 | |||
58 | The read file is read-only. Reading gives you the current I/O input | ||
59 | if the corresponding output is set as 1, otherwise the current output | ||
60 | value, that is to say 0. | ||
61 | |||
62 | The write file is read/write. Writing a value outputs it on the I/O | ||
63 | port. Reading returns the last written value. As it is not possible | ||
64 | to read this value from the chip, you need to write at least once to | ||
65 | this file before you can read back from it. | ||