| 1 | Kernel driver `mic74.o' |
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| 2 | ========================= |
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| 3 | |
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| 4 | Status: Beta |
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| 5 | |
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| 6 | Supported chips: |
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| 7 | * Micrel MIC74 |
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| 8 | Prefix: 'mic74' |
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| 9 | Addresses scanned: I2C 0x20 - 0x27 |
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| 10 | Datasheet: Publicly available at the Micrel website |
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| 11 | http://www.micrel.com/ |
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| 12 | |
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| 13 | Authors: zebo25 |
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| 14 | mds (cleanups and this doc) |
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| 15 | |
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| 16 | Module Parameters |
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| 17 | ----------------- |
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| 18 | |
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| 19 | |
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| 20 | Description |
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| 21 | ----------- |
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| 22 | The MIC74 is an 8-bit I/O expander for the I2C bus. |
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| 23 | Semiconductors. It is designed to provide a byte I2C interface to up to 8 |
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| 24 | separate devices. |
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| 25 | |
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| 26 | This device consists of a quasi-bidirectionnal port. Each of the eight I/Os |
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| 27 | can be independently used as an input or output. |
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| 28 | |
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| 29 | The driver does not initialize the ports, they will be at their |
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| 30 | power-up defaults, or however the BIOS programmed them. |
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| 31 | |
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| 32 | For more information see the datasheet. |
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| 33 | |
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| 34 | |
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| 35 | Accessing MIC74 via /proc interface |
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| 36 | ------------------------------------- |
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| 37 | |
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| 38 | ! Be careful ! |
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| 39 | The chip is plainly impossible to detect ! Stupid chip. |
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| 40 | So every chip with adress in the interval [20..27] could be |
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| 41 | detected as an MIC74 or a PCF8574. Don't load both drivers. |
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| 42 | If you have other chips in this address |
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| 43 | range, the workaround is to load this module after the one |
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| 44 | for your others chips. |
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| 45 | |
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| 46 | On detection, directories are created for each detected chip: |
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| 47 | |
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| 48 | /proc/sys/dev/sensors/mic74-<0>-<1>/ |
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| 49 | where <0> is the bus the chip was detected on (e. g. i2c-0) |
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| 50 | and <1> the chip address [20..27]: |
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| 51 | ./mic74-i2c-0-27/ |
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| 52 | |
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| 53 | Inside these directories, there are seven files each, |
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| 54 | one for each of the seven registers in the device. |
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| 55 | |
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| 56 | At this point you really need the datasheet. |
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| 57 | It should be self-explanatory which file is for which register. |
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