linux/Documentation/hwmon/pcf8591
<<
>>
Prefs
   1Kernel driver pcf8591
   2=====================
   3
   4Supported 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
  11Authors:
  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
  17Description
  18-----------
  19
  20The PCF8591 is an 8-bit A/D and D/A converter (4 analog inputs and one
  21analog output) for the I2C bus produced by Philips Semiconductors (now NXP).
  22It is designed to provide a byte I2C interface to up to 4 separate devices.
  23
  24The PCF8591 has 4 analog inputs programmable as single-ended or
  25differential 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
  44See the datasheet for details.
  45
  46Module 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
  58Accessing PCF8591 via /sys interface
  59-------------------------------------
  60
  61The PCF8591 is plainly impossible to detect! Thus the driver won't even
  62try. You have to explicitly instantiate the device at the relevant
  63address (in the interval [0x48..0x4f]) either through platform data, or
  64using the sysfs interface. See Documentation/i2c/instantiating-devices
  65for details.
  66
  67Directories are being created for each instantiated PCF8591:
  68
  69/sys/bus/i2c/devices/<0>-<1>/
  70where <0> is the bus the chip is connected to (e. g. i2c-0)
  71and <1> the chip address ([48..4f])
  72
  73Inside these directories, there are such files:
  74in0_input, in1_input, in2_input, in3_input, out0_enable, out0_output, name
  75
  76Name contains chip name.
  77
  78The in0_input, in1_input, in2_input and in3_input files are RO. Reading gives
  79the value of the corresponding channel. Depending on the current analog inputs
  80configuration, files in2_input and in3_input may not exist. Values range
  81from 0 to 255 for single ended inputs and -128 to +127 for differential inputs
  82(8-bit ADC).
  83
  84The 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
  87The out0_output file is RW. Writing a number between 0 and 255 (8-bit DAC), send
  88the value to the digital-to-analog converter. Note that a voltage will
  89only appears on AOUT pin if aout0_enable equals 1. Reading returns the last
  90value written.
  91
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.