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1 | Kernel driver pcf8591 |
2 | ===================== | |
3 | ||
4 | Supported chips: | |
b04f2f7d | 5 | |
afc31875 | 6 | * Philips/NXP PCF8591 |
b04f2f7d | 7 | |
7f15b664 | 8 | Prefix: 'pcf8591' |
b04f2f7d | 9 | |
6dfee853 | 10 | Addresses scanned: none |
b04f2f7d | 11 | |
afc31875 | 12 | Datasheet: Publicly available at the NXP website |
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13 | |
14 | http://www.nxp.com/pip/PCF8591_6.html | |
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15 | |
16 | Authors: | |
b04f2f7d MCC |
17 | - Aurelien Jarno <aurelien@aurel32.net> |
18 | - valuable contributions by Jan M. Sendler <sendler@sendler.de>, | |
19 | - Jean Delvare <jdelvare@suse.de> | |
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20 | |
21 | ||
22 | Description | |
23 | ----------- | |
afc31875 | 24 | |
7f15b664 | 25 | The PCF8591 is an 8-bit A/D and D/A converter (4 analog inputs and one |
afc31875 JD |
26 | analog output) for the I2C bus produced by Philips Semiconductors (now NXP). |
27 | It is designed to provide a byte I2C interface to up to 4 separate devices. | |
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28 | |
29 | The PCF8591 has 4 analog inputs programmable as single-ended or | |
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30 | differential inputs: |
31 | ||
7f15b664 | 32 | - mode 0 : four single ended inputs |
b04f2f7d | 33 | Pins AIN0 to AIN3 are single ended inputs for channels 0 to 3 |
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34 | |
35 | - mode 1 : three differential inputs | |
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36 | Pins AIN3 is the common negative differential input |
37 | Pins AIN0 to AIN2 are positive differential inputs for channels 0 to 2 | |
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38 | |
39 | - mode 2 : single ended and differential mixed | |
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40 | Pins AIN0 and AIN1 are single ended inputs for channels 0 and 1 |
41 | Pins AIN2 is the positive differential input for channel 3 | |
42 | Pins AIN3 is the negative differential input for channel 3 | |
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43 | |
44 | - mode 3 : two differential inputs | |
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45 | Pins AIN0 is the positive differential input for channel 0 |
46 | Pins AIN1 is the negative differential input for channel 0 | |
47 | Pins AIN2 is the positive differential input for channel 1 | |
48 | Pins AIN3 is the negative differential input for channel 1 | |
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49 | |
50 | See the datasheet for details. | |
51 | ||
52 | Module parameters | |
53 | ----------------- | |
54 | ||
55 | * input_mode int | |
56 | ||
57 | Analog input mode: | |
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58 | |
59 | - 0 = four single ended inputs | |
60 | - 1 = three differential inputs | |
61 | - 2 = single ended and differential mixed | |
62 | - 3 = two differential inputs | |
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63 | |
64 | ||
65 | Accessing PCF8591 via /sys interface | |
66 | ------------------------------------- | |
67 | ||
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68 | The PCF8591 is plainly impossible to detect! Thus the driver won't even |
69 | try. You have to explicitly instantiate the device at the relevant | |
70 | address (in the interval [0x48..0x4f]) either through platform data, or | |
ccf988b6 | 71 | using the sysfs interface. See Documentation/i2c/instantiating-devices.rst |
6dfee853 | 72 | for details. |
7f15b664 | 73 | |
6dfee853 | 74 | Directories are being created for each instantiated PCF8591: |
7f15b664 | 75 | |
afc31875 | 76 | /sys/bus/i2c/devices/<0>-<1>/ |
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77 | where <0> is the bus the chip is connected to (e. g. i2c-0) |
78 | and <1> the chip address ([48..4f]) | |
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79 | |
80 | Inside these directories, there are such files: | |
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81 | |
82 | in0_input, in1_input, in2_input, in3_input, out0_enable, out0_output, name | |
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83 | |
84 | Name contains chip name. | |
85 | ||
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86 | The in0_input, in1_input, in2_input and in3_input files are RO. Reading gives |
87 | the value of the corresponding channel. Depending on the current analog inputs | |
88 | configuration, files in2_input and in3_input may not exist. Values range | |
89 | from 0 to 255 for single ended inputs and -128 to +127 for differential inputs | |
90 | (8-bit ADC). | |
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91 | |
92 | The out0_enable file is RW. Reading gives "1" for analog output enabled and | |
93 | "0" for analog output disabled. Writing accepts "0" and "1" accordingly. | |
94 | ||
95 | The out0_output file is RW. Writing a number between 0 and 255 (8-bit DAC), send | |
96 | the value to the digital-to-analog converter. Note that a voltage will | |
97 | only appears on AOUT pin if aout0_enable equals 1. Reading returns the last | |
98 | value written. |