Kernel driver `pcf8574.o' ======================== Status: Status: Complete; Supported chips: * Philips PCF8574 Prefix: `pcf8574' Addresses scanned: I2C 0x20 - 0x27 (inclusive) Datasheet: Publicly available at the Philips Semiconductor website http://semiconductors.philips.com/ * Philips PCF8574A Prefix: `pcf8574a' Addresses scanned: I2C 0x38 - 0x3f (inclusive) Datasheet: Publicly available at the Philips Semiconductor website http://semiconductors.philips.com/ Authors: Frodo Looijaard , Philip Edelbrock , and Dan Eaton Module Parameters ----------------- * force: short array (min = 1, max = 48) List of adapter,address pairs to boldly assume to be present * force_pcf8574: short array (min = 1, max = 48) List of adapter,address pairs which are unquestionably assumed to contain a `pcf8574' chip * ignore: short array (min = 1, max = 48) List of adapter,address pairs not to scan * ignore_range: short array (min = 1, max = 48) List of adapter,start-addr,end-addr triples not to scan * probe: short array (min = 1, max = 48) List of adapter,address pairs to scan additionally * probe_range: short array (min = 1, max = 48) List of adapter,start-addr,end-addr triples to scan additionally Description ----------- The PCF8574(A) is an 8-bit I/O expander for the I2C bus produced by Philips Semiconductors. It is designed to provide a byte I2C interface to up to 16 separate devices (8 x PCF8574 and 8 x PCF8574A). This device consists of a quasi-bidirectionnal port. Each of the eight I/Os can be independently used as an input or output. To setup an I/O as an input, you have to write a 1 to the corresponding output. For more informations see the datasheet. Accessing PCF8574(A) via /proc interface ------------------------------------- ! Be careful ! The PCF8574(A) is plainly impossible to detect ! Stupid chip. So every chip with adress in the interval [20..27] and (38..3f) are detected as PCF8574(A). 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 PCF8574(A): /proc/sys/dev/sensors/pcf8574-<0>-<1>/ where <0> is the bus the chip was detected on (e. g. i2c-0) and <1> the chip address ([20..27] or [38..3f]): ./pcf8574-i2c-0-27/ Inside these directories, there are two files each: read and write. The read file is read-only. Reading gives you the current I/O input if the corresponding output is set as 1, otherwise the current output value, that is to say 0. The write file is read/write. Writing a value outputs it on the I/O port. Reading return the last written value. On module initialization the chip is configured as eight I/Os input (all outputs to 1), so you can connect any circuit to the PCF8574(A) without to be afraid of short-circuit. Chip Features ------------- Chip `pcf8574' LABEL LABEL CLASS COMPUTE CLASS ACCESS MAGNITUDE read NONE NONE R 0 write NONE NONE RW 0 LABEL FEATURE SYMBOL SYSCTL FILE:OFFSET read SENSORS_PCF8591_READ read:1 write SENSORS_PCF8591_WRITE write:1