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- 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.
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