mirror of https://github.com/Qortal/Brooklyn
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
98 lines
3.1 KiB
98 lines
3.1 KiB
Kernel driver pcf8591 |
|
===================== |
|
|
|
Supported chips: |
|
|
|
* Philips/NXP PCF8591 |
|
|
|
Prefix: 'pcf8591' |
|
|
|
Addresses scanned: none |
|
|
|
Datasheet: Publicly available at the NXP website |
|
|
|
http://www.nxp.com/pip/PCF8591_6.html |
|
|
|
Authors: |
|
- Aurelien Jarno <[email protected]> |
|
- valuable contributions by Jan M. Sendler <[email protected]>, |
|
- Jean Delvare <[email protected]> |
|
|
|
|
|
Description |
|
----------- |
|
|
|
The PCF8591 is an 8-bit A/D and D/A converter (4 analog inputs and one |
|
analog output) for the I2C bus produced by Philips Semiconductors (now NXP). |
|
It is designed to provide a byte I2C interface to up to 4 separate devices. |
|
|
|
The PCF8591 has 4 analog inputs programmable as single-ended or |
|
differential inputs: |
|
|
|
- mode 0 : four single ended inputs |
|
Pins AIN0 to AIN3 are single ended inputs for channels 0 to 3 |
|
|
|
- mode 1 : three differential inputs |
|
Pins AIN3 is the common negative differential input |
|
Pins AIN0 to AIN2 are positive differential inputs for channels 0 to 2 |
|
|
|
- mode 2 : single ended and differential mixed |
|
Pins AIN0 and AIN1 are single ended inputs for channels 0 and 1 |
|
Pins AIN2 is the positive differential input for channel 3 |
|
Pins AIN3 is the negative differential input for channel 3 |
|
|
|
- mode 3 : two differential inputs |
|
Pins AIN0 is the positive differential input for channel 0 |
|
Pins AIN1 is the negative differential input for channel 0 |
|
Pins AIN2 is the positive differential input for channel 1 |
|
Pins AIN3 is the negative differential input for channel 1 |
|
|
|
See the datasheet for details. |
|
|
|
Module parameters |
|
----------------- |
|
|
|
* input_mode int |
|
|
|
Analog input mode: |
|
|
|
- 0 = four single ended inputs |
|
- 1 = three differential inputs |
|
- 2 = single ended and differential mixed |
|
- 3 = two differential inputs |
|
|
|
|
|
Accessing PCF8591 via /sys interface |
|
------------------------------------- |
|
|
|
The PCF8591 is plainly impossible to detect! Thus the driver won't even |
|
try. You have to explicitly instantiate the device at the relevant |
|
address (in the interval [0x48..0x4f]) either through platform data, or |
|
using the sysfs interface. See Documentation/i2c/instantiating-devices.rst |
|
for details. |
|
|
|
Directories are being created for each instantiated PCF8591: |
|
|
|
/sys/bus/i2c/devices/<0>-<1>/ |
|
where <0> is the bus the chip is connected to (e. g. i2c-0) |
|
and <1> the chip address ([48..4f]) |
|
|
|
Inside these directories, there are such files: |
|
|
|
in0_input, in1_input, in2_input, in3_input, out0_enable, out0_output, name |
|
|
|
Name contains chip name. |
|
|
|
The in0_input, in1_input, in2_input and in3_input files are RO. Reading gives |
|
the value of the corresponding channel. Depending on the current analog inputs |
|
configuration, files in2_input and in3_input may not exist. Values range |
|
from 0 to 255 for single ended inputs and -128 to +127 for differential inputs |
|
(8-bit ADC). |
|
|
|
The out0_enable file is RW. Reading gives "1" for analog output enabled and |
|
"0" for analog output disabled. Writing accepts "0" and "1" accordingly. |
|
|
|
The out0_output file is RW. Writing a number between 0 and 255 (8-bit DAC), send |
|
the value to the digital-to-analog converter. Note that a voltage will |
|
only appears on AOUT pin if aout0_enable equals 1. Reading returns the last |
|
value written.
|
|
|