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authorWolfram Sang <w.sang@pengutronix.de>2009-09-18 16:45:48 -0400
committerJean Delvare <khali@linux-fr.org>2009-09-18 16:45:48 -0400
commit8f67eeb0b44cde19216955975ffef8513a87c0c0 (patch)
treec848851a7494b72038f24beca93362755567e8cc /Documentation/i2c
parent4ba2ccb83e03077bb94f8848ee573f1e27cea969 (diff)
i2c/chips: Remove deprecated pcf8575 driver
The pcf8575 driver in drivers/i2c/chips which just exports its register to sysfs is superseded by drivers/gpio/pcf857x.c which properly uses the gpiolib. As this driver has been deprecated for more than a year, finally remove it. Signed-off-by: Wolfram Sang <w.sang@pengutronix.de> Cc: Bart Van Assche <bart.vanassche@gmail.com> Signed-off-by: Jean Delvare <khali@linux-fr.org>
Diffstat (limited to 'Documentation/i2c')
-rw-r--r--Documentation/i2c/chips/pcf857569
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diff --git a/Documentation/i2c/chips/pcf8575 b/Documentation/i2c/chips/pcf8575
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1About the PCF8575 chip and the pcf8575 kernel driver
2====================================================
3
4The PCF8575 chip is produced by the following manufacturers:
5
6 * Philips NXP
7 http://www.nxp.com/#/pip/cb=[type=product,path=50807/41735/41850,final=PCF8575_3]|pip=[pip=PCF8575_3][0]
8
9 * Texas Instruments
10 http://focus.ti.com/docs/prod/folders/print/pcf8575.html
11
12
13Some vendors sell small PCB's with the PCF8575 mounted on it. You can connect
14such a board to a Linux host via e.g. an USB to I2C interface. Examples of
15PCB boards with a PCF8575:
16
17 * SFE Breakout Board for PCF8575 I2C Expander by RobotShop
18 http://www.robotshop.ca/home/products/robot-parts/electronics/adapters-converters/sfe-pcf8575-i2c-expander-board.html
19
20 * Breakout Board for PCF8575 I2C Expander by Spark Fun Electronics
21 http://www.sparkfun.com/commerce/product_info.php?products_id=8130
22
23
24Description
25-----------
26The PCF8575 chip is a 16-bit I/O expander for the I2C bus. Up to eight of
27these chips can be connected to the same I2C bus. You can find this
28chip on some custom designed hardware, but you won't find it on PC
29motherboards.
30
31The PCF8575 chip consists of a 16-bit quasi-bidirectional port and an I2C-bus
32interface. Each of the sixteen I/O's can be independently used as an input or
33an output. To set up an I/O pin as an input, you have to write a 1 to the
34corresponding output.
35
36For more information please see the datasheet.
37
38
39Detection
40---------
41
42There is no method known to detect whether a chip on a given I2C address is
43a PCF8575 or whether it is any other I2C device, so you have to pass the I2C
44bus and address of the installed PCF8575 devices explicitly to the driver at
45load time via the force=... parameter.
46
47/sys interface
48--------------
49
50For each address on which a PCF8575 chip was found or forced the following
51files will be created under /sys:
52* /sys/bus/i2c/devices/<bus>-<address>/read
53* /sys/bus/i2c/devices/<bus>-<address>/write
54where bus is the I2C bus number (0, 1, ...) and address is the four-digit
55hexadecimal representation of the 7-bit I2C address of the PCF8575
56(0020 .. 0027).
57
58The read file is read-only. Reading it will trigger an I2C read and will hence
59report the current input state for the pins configured as inputs, and the
60current output value for the pins configured as outputs.
61
62The write file is read-write. Writing a value to it will configure all pins
63as output for which the corresponding bit is zero. Reading the write file will
64return the value last written, or -EAGAIN if no value has yet been written to
65the write file.
66
67On module initialization the configuration of the chip is not changed -- the
68chip is left in the state it was already configured in through either power-up
69or through previous I2C write actions.