1Kernel driver pcf8591 2===================== 3 4Supported chips: 5 6 * Philips/NXP PCF8591 7 8 Prefix: 'pcf8591' 9 10 Addresses scanned: none 11 12 Datasheet: Publicly available at the NXP website 13 14 http://www.nxp.com/pip/PCF8591_6.html 15 16Authors: 17 - Aurelien Jarno <aurelien@aurel32.net> 18 - valuable contributions by Jan M. Sendler <sendler@sendler.de>, 19 - Jean Delvare <jdelvare@suse.de> 20 21 22Description 23----------- 24 25The PCF8591 is an 8-bit A/D and D/A converter (4 analog inputs and one 26analog output) for the I2C bus produced by Philips Semiconductors (now NXP). 27It is designed to provide a byte I2C interface to up to 4 separate devices. 28 29The PCF8591 has 4 analog inputs programmable as single-ended or 30differential inputs: 31 32- mode 0 : four single ended inputs 33 Pins AIN0 to AIN3 are single ended inputs for channels 0 to 3 34 35- mode 1 : three differential inputs 36 Pins AIN3 is the common negative differential input 37 Pins AIN0 to AIN2 are positive differential inputs for channels 0 to 2 38 39- mode 2 : single ended and differential mixed 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 43 44- mode 3 : two differential inputs 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 49 50See the datasheet for details. 51 52Module parameters 53----------------- 54 55* input_mode int 56 57 Analog input mode: 58 59 - 0 = four single ended inputs 60 - 1 = three differential inputs 61 - 2 = single ended and differential mixed 62 - 3 = two differential inputs 63 64 65Accessing PCF8591 via /sys interface 66------------------------------------- 67 68The PCF8591 is plainly impossible to detect! Thus the driver won't even 69try. You have to explicitly instantiate the device at the relevant 70address (in the interval [0x48..0x4f]) either through platform data, or 71using the sysfs interface. See Documentation/i2c/instantiating-devices.rst 72for details. 73 74Directories are being created for each instantiated PCF8591: 75 76/sys/bus/i2c/devices/<0>-<1>/ 77 where <0> is the bus the chip is connected to (e. g. i2c-0) 78 and <1> the chip address ([48..4f]) 79 80Inside these directories, there are such files: 81 82 in0_input, in1_input, in2_input, in3_input, out0_enable, out0_output, name 83 84Name contains chip name. 85 86The in0_input, in1_input, in2_input and in3_input files are RO. Reading gives 87the value of the corresponding channel. Depending on the current analog inputs 88configuration, files in2_input and in3_input may not exist. Values range 89from 0 to 255 for single ended inputs and -128 to +127 for differential inputs 90(8-bit ADC). 91 92The 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 95The out0_output file is RW. Writing a number between 0 and 255 (8-bit DAC), send 96the value to the digital-to-analog converter. Note that a voltage will 97only appears on AOUT pin if aout0_enable equals 1. Reading returns the last 98value written. 99