Root/
1 | Kernel driver pcf8591 |
2 | ===================== |
3 | |
4 | Supported chips: |
5 | * Philips/NXP PCF8591 |
6 | Prefix: 'pcf8591' |
7 | Addresses scanned: none |
8 | Datasheet: Publicly available at the NXP website |
9 | http://www.nxp.com/pip/PCF8591_6.html |
10 | |
11 | Authors: |
12 | Aurelien Jarno <aurelien@aurel32.net> |
13 | valuable contributions by Jan M. Sendler <sendler@sendler.de>, |
14 | Jean Delvare <khali@linux-fr.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 | The PCF8591 is plainly impossible to detect! Thus the driver won't even |
62 | try. You have to explicitly instantiate the device at the relevant |
63 | address (in the interval [0x48..0x4f]) either through platform data, or |
64 | using the sysfs interface. See Documentation/i2c/instantiating-devices |
65 | for details. |
66 | |
67 | Directories are being created for each instantiated PCF8591: |
68 | |
69 | /sys/bus/i2c/devices/<0>-<1>/ |
70 | where <0> is the bus the chip is connected to (e. g. i2c-0) |
71 | and <1> the chip address ([48..4f]) |
72 | |
73 | Inside these directories, there are such files: |
74 | in0_input, in1_input, in2_input, in3_input, out0_enable, out0_output, name |
75 | |
76 | Name contains chip name. |
77 | |
78 | The in0_input, in1_input, in2_input and in3_input files are RO. Reading gives |
79 | the value of the corresponding channel. Depending on the current analog inputs |
80 | configuration, files in2_input and in3_input may not exist. Values range |
81 | from 0 to 255 for single ended inputs and -128 to +127 for differential inputs |
82 | (8-bit ADC). |
83 | |
84 | The out0_enable file is RW. Reading gives "1" for analog output enabled and |
85 | "0" for analog output disabled. Writing accepts "0" and "1" accordingly. |
86 | |
87 | The out0_output file is RW. Writing a number between 0 and 255 (8-bit DAC), send |
88 | the value to the digital-to-analog converter. Note that a voltage will |
89 | only appears on AOUT pin if aout0_enable equals 1. Reading returns the last |
90 | value written. |
91 |
Branches:
ben-wpan
ben-wpan-stefan
javiroman/ks7010
jz-2.6.34
jz-2.6.34-rc5
jz-2.6.34-rc6
jz-2.6.34-rc7
jz-2.6.35
jz-2.6.36
jz-2.6.37
jz-2.6.38
jz-2.6.39
jz-3.0
jz-3.1
jz-3.11
jz-3.12
jz-3.13
jz-3.15
jz-3.16
jz-3.18-dt
jz-3.2
jz-3.3
jz-3.4
jz-3.5
jz-3.6
jz-3.6-rc2-pwm
jz-3.9
jz-3.9-clk
jz-3.9-rc8
jz47xx
jz47xx-2.6.38
master
Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9