Based on kernel version 4.16.1. Page generated on 2018-04-09 11:53 EST.
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 <jdelvare@suse.de> 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.