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Mark D. Studebaker
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git-svn-id: http://lm-sensors.org/svn/lm-sensors/trunk@1253 7894878c-1315-0410-8ee3-d5d059ff63e0
128 lines
5.1 KiB
Plaintext
128 lines
5.1 KiB
Plaintext
Kernel driver `pcf8591.o'
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========================
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Status: Status: Complete; Beta.
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Supported chips:
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* Philips PCF8591
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Prefix: `pcf8591'
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Addresses scanned: I2C 0x48 - 0x4f (inclusive)
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Datasheet: Publicly available at the Philips Semiconductor website
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http://semiconductors.philips.com/
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Author: Aurelien Jarno <aurelien@aurel32.net>
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valuable contributions by Jan M. Sendler <sendler@sendler.de>
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Module Parameters
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-----------------
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* force: short array (min = 1, max = 48)
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List of adapter,address pairs to boldly assume to be present
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* force_pcf8591: short array (min = 1, max = 48)
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List of adapter,address pairs which are unquestionably assumed to
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contain a `pcf8591' chip
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* ignore: short array (min = 1, max = 48)
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List of adapter,address pairs not to scan
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* ignore_range: short array (min = 1, max = 48)
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List of adapter,start-addr,end-addr triples not to scan
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* probe: short array (min = 1, max = 48)
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List of adapter,address pairs to scan additionally
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* probe_range: short array (min = 1, max = 48)
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List of adapter,start-addr,end-addr triples to scan additionally
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Description
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-----------
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The PCF8591 is an 8-bit A/D and D/A converter (4 analog input and one
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analog ouput) for the I2C bus produced by Philips Semiconductors. It
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is designed to provide a byte I2C interface to up to 4 separate devices.
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The PCF8591 has 4 analog inputs programmable as single-ended or
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differential inputs :
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- mode 0 : four single ended inputs
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Pins AIN0 to AIN3 are single ended inputs for channels 0 to 3
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- mode 1 : three differential inputs
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Pins AIN3 is the common negative differential input
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Pins AIN0 to AIN2 are positive differential inputs for channels 0 to 2
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- mode 2 : single ended and differential mixed
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Pins AIN0 and AIN1 are single ended inputs for channels 0 and 1
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Pins AIN2 is the positive differential input for channel 3
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Pins AIN3 is the negative differential input for channel 3
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- mode 3 : four differential inputs
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Pins AIN0 is the positive differential input for channel 0
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Pins AIN1 is the negative differential input for channel 0
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Pins AIN2 is the positive differential input for channel 1
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Pins AIN3 is the negative differential input for channel 1
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For more informations see the datasheet.
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Accessing PCF8591 via /proc interface
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-------------------------------------
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! Be careful !
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The PCF8591 is plainly impossible to detect ! Stupid chip.
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So every chip with adress in the interval [48..4f] are
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detected as PCF8591. If you have other chips in this address
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range, the workaround is to load this module after the one
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for your others chips.
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On detection (i.e. insmod, modprobe et al.), directories are being
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created for each detected PCF8591:
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/proc/sys/dev/sensors/pcf8591-<0>-<1>/
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where <0> is the bus the chip was detected on (e. g. i2c-0)
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and <1> the chip address ([48..4f]): ./pcf8591-i2c-0-48/
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Inside these directories, there are five files each:
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ain_conf, ch0, ch1, ch2, ch3, aout_enable, aout.
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The ain_conf file is rw. Reading gives you the current analog inputs
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configuration, and writing configure the analog inputs. It must be
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a number between 0 and 3., other values are ignored. For the different
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modes, see above in the description.
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The ch0, ch1, ch2 and ch3 files are ro. Reading gives the value
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of the corresponding channel. Depending on the current analog inputs
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configuration, channel ch2 and/or ch3 may are not used by the chip
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and so read as 0. Values range are from 0 to 255 for single
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ended inputs and -128 to +127 for differential inputs (8-bit ADC).
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The aout_enable is rw. Reading gives "0" for analog output enabled and
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"1" for analog output disabled. Writing accepts "0" and "1" accordingly.
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The aout is rw. Writing a number between 0 and 255 (8-bit DAC), send
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the value to the digital-to-analog converter. Note that a voltage will
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only appears on AOUT pin if aout_enable equals 1. Reading return the last
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value written.
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On module initialization the chip is configured as followed :
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- four single ended differential inputs
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- analog output set to 0 and enabled
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Chip Features
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-------------
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Chip `pcf8591'
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LABEL LABEL CLASS COMPUTE CLASS ACCESS MAGNITUDE
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ain_conf NONE NONE RW 0
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ch0 NONE NONE R 0
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ch1 NONE NONE R 0
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ch2 NONE NONE R 0
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ch3 NONE NONE R 0
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aout_enable NONE NONE RW 0
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aout NONE NONE RW 0
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LABEL FEATURE SYMBOL SYSCTL FILE:OFFSET
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ain_conf SENSORS_PCF8591_AIN_CONF ain_conf:1
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ch0 SENSORS_PCF8591_CH0 ain_ch0:1
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ch1 SENSORS_PCF8591_CH1 ain_ch1:1
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ch2 SENSORS_PCF8591_CH2 ain_ch2:1
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ch3 SENSORS_PCF8591_CH3 ain_ch3:1
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aout_enable SENSORS_PCF8591_AOUT_ENABLE aout_enable:1
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aout SENSORS_PCF8591_AOUT aout:1
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