1Kernel driver pcf8591 2===================== 3 4Supported chips: 5 * Philips/NXP PCF8591 6 Prefix: 'pcf8591' 7 Addresses scanned: I2C 0x48 - 0x4f 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 61! Be careful ! 62The PCF8591 is plainly impossible to detect! Stupid chip. 63So every chip with address in the interval [0x48..0x4f] is 64detected as PCF8591. If you have other chips in this address 65range, the workaround is to load this module after the one 66for your others chips. 67 68On detection (i.e. insmod, modprobe et al.), directories are being 69created for each detected PCF8591: 70 71/sys/bus/i2c/devices/<0>-<1>/ 72where <0> is the bus the chip was detected on (e. g. i2c-0) 73and <1> the chip address ([48..4f]) 74 75Inside these directories, there are such files: 76in0_input, in1_input, in2_input, in3_input, out0_enable, out0_output, name 77 78Name contains chip name. 79 80The in0_input, in1_input, in2_input and in3_input files are RO. Reading gives 81the value of the corresponding channel. Depending on the current analog inputs 82configuration, files in2_input and in3_input may not exist. Values range 83from 0 to 255 for single ended inputs and -128 to +127 for differential inputs 84(8-bit ADC). 85 86The out0_enable file is RW. Reading gives "1" for analog output enabled and 87"0" for analog output disabled. Writing accepts "0" and "1" accordingly. 88 89The out0_output file is RW. Writing a number between 0 and 255 (8-bit DAC), send 90the value to the digital-to-analog converter. Note that a voltage will 91only appears on AOUT pin if aout0_enable equals 1. Reading returns the last 92value written. 93