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Based on kernel version 2.6.34. Page generated on 2010-05-31 16:02 EST.

1	Kernel driver pcf8591
2	=====================
3	
4	Supported chips:
5	  * Philips/NXP PCF8591
6	    Prefix: 'pcf8591'
7	    Addresses scanned: I2C 0x48 - 0x4f
8	    Datasheet: Publicly available at the NXP website
9	               http://www.nxp.com/pip/PCF8591_6.html
10	
11	Authors:
12	        Aurelien Jarno <aurelien[AT]aurel32[DOT]net>
13	        valuable contributions by Jan M. Sendler <sendler[AT]sendler[DOT]de>,
14	        Jean Delvare <khali[AT]linux-fr[DOT]org>
15	
16	
17	Description
18	-----------
19	
20	The PCF8591 is an 8-bit A/D and D/A converter (4 analog inputs and one
21	analog output) for the I2C bus produced by Philips Semiconductors (now NXP).
22	It is designed to provide a byte I2C interface to up to 4 separate devices.
23	
24	The PCF8591 has 4 analog inputs programmable as single-ended or
25	differential inputs :
26	- mode 0 : four single ended inputs
27	        Pins AIN0 to AIN3 are single ended inputs for channels 0 to 3
28	
29	- mode 1 : three differential inputs
30	        Pins AIN3 is the common negative differential input
31	        Pins AIN0 to AIN2 are positive differential inputs for channels 0 to 2
32	
33	- mode 2 : single ended and differential mixed
34	        Pins AIN0 and AIN1 are single ended inputs for channels 0 and 1
35	        Pins AIN2 is the positive differential input for channel 3
36	        Pins AIN3 is the negative differential input for channel 3
37	
38	- mode 3 : two differential inputs
39	        Pins AIN0 is the positive differential input for channel 0
40	        Pins AIN1 is the negative differential input for channel 0
41	        Pins AIN2 is the positive differential input for channel 1
42	        Pins AIN3 is the negative differential input for channel 1
43	
44	See the datasheet for details.
45	
46	Module parameters
47	-----------------
48	
49	* input_mode int
50	
51	    Analog input mode:
52	         0 = four single ended inputs
53	         1 = three differential inputs
54	         2 = single ended and differential mixed
55	         3 = two differential inputs
56	
57	
58	Accessing PCF8591 via /sys interface
59	-------------------------------------
60	
61	! Be careful !
62	The PCF8591 is plainly impossible to detect! Stupid chip.
63	So every chip with address in the interval [0x48..0x4f] is
64	detected as PCF8591. If you have other chips in this address
65	range, the workaround is to load this module after the one
66	for your others chips.
67	
68	On detection (i.e. insmod, modprobe et al.), directories are being
69	created for each detected PCF8591:
70	
71	/sys/bus/i2c/devices/<0>-<1>/
72	where <0> is the bus the chip was detected on (e. g. i2c-0)
73	and <1> the chip address ([48..4f])
74	
75	Inside these directories, there are such files:
76	in0_input, in1_input, in2_input, in3_input, out0_enable, out0_output, name
77	
78	Name contains chip name.
79	
80	The in0_input, in1_input, in2_input and in3_input files are RO. Reading gives
81	the value of the corresponding channel. Depending on the current analog inputs
82	configuration, files in2_input and in3_input may not exist. Values range
83	from 0 to 255 for single ended inputs and -128 to +127 for differential inputs
84	(8-bit ADC).
85	
86	The out0_enable file is RW. Reading gives "1" for analog output enabled and
87	"0" for analog output disabled. Writing accepts "0" and "1" accordingly.
88	
89	The out0_output file is RW. Writing a number between 0 and 255 (8-bit DAC), send
90	the value to the digital-to-analog converter. Note that a voltage will
91	only appears on AOUT pin if aout0_enable equals 1. Reading returns the last
92	value written.
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