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diff --git a/Documentation/i2c/chips/pcf8591 b/Documentation/i2c/chips/pcf8591 new file mode 100644 index 00000000000..5628fcf4207 --- /dev/null +++ b/Documentation/i2c/chips/pcf8591 @@ -0,0 +1,90 @@ +Kernel driver pcf8591 +===================== + +Supported chips: + * Philips PCF8591 + Prefix: 'pcf8591' + Addresses scanned: I2C 0x48 - 0x4f + Datasheet: Publicly available at the Philips Semiconductor website + http://www.semiconductors.philips.com/pip/PCF8591P.html + +Authors: + Aurelien Jarno <aurelien@aurel32.net> + valuable contributions by Jan M. Sendler <sendler@sendler.de>, + Jean Delvare <khali@linux-fr.org> + + +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. 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 +------------------------------------- + +! Be careful ! +The PCF8591 is plainly impossible to detect ! Stupid chip. +So every chip with address in the interval [48..4f] is +detected as PCF8591. If you have other chips in this address +range, the workaround is to load this module after the one +for your others chips. + +On detection (i.e. insmod, modprobe et al.), directories are being +created for each detected PCF8591: + +/sys/bus/devices/<0>-<1>/ +where <0> is the bus the chip was detected on (e. g. i2c-0) +and <1> the chip address ([48..4f]) + +Inside these directories, there are such files: +in0, in1, in2, in3, out0_enable, out0_output, name + +Name contains chip name. + +The in0, in1, in2 and in3 files are RO. Reading gives the value of the +corresponding channel. Depending on the current analog inputs configuration, +files in2 and/or in3 do not exist. Values range are 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. |