git://bbs.cooldavid.org / net-next-2.6.git / blame
| Commit | Line | Data |
|---|---|---|
| 69dd204b BG |
1 | Kernel driver pca9539 |
| 2 | ===================== | |
| 3 | ||
| b72540c3 | 4 | NOTE: this driver is deprecated and will be dropped soon, use |
| 5 | drivers/gpio/pca9539.c instead. | |
| 6 | ||
| 69dd204b BG |
7 | Supported chips: |
| 8 | * Philips PCA9539 | |
| 9 | Prefix: 'pca9539' | |
| 3d63430a | 10 | Addresses scanned: none |
| 69dd204b BG |
11 | Datasheet: |
| 12 | http://www.semiconductors.philips.com/acrobat/datasheets/PCA9539_2.pdf | |
| 13 | ||
| 14 | Author: Ben Gardner <bgardner@wabtec.com> | |
| 15 | ||
| 16 | ||
| 17 | Description | |
| 18 | ----------- | |
| 19 | ||
| 20 | The Philips PCA9539 is a 16 bit low power I/O device. | |
| 21 | All 16 lines can be individually configured as an input or output. | |
| 22 | The input sense can also be inverted. | |
| 23 | The 16 lines are split between two bytes. | |
| 24 | ||
| 25 | ||
| 3d63430a JD |
26 | Detection |
| 27 | --------- | |
| 28 | ||
| 29 | The PCA9539 is difficult to detect and not commonly found in PC machines, | |
| 30 | so you have to pass the I2C bus and address of the installed PCA9539 | |
| 31 | devices explicitly to the driver at load time via the force=... parameter. | |
| 32 | ||
| 33 | ||
| 69dd204b BG |
34 | Sysfs entries |
| 35 | ------------- | |
| 36 | ||
| 37 | Each is a byte that maps to the 8 I/O bits. | |
| 38 | A '0' suffix is for bits 0-7, while '1' is for bits 8-15. | |
| 39 | ||
| 40 | input[01] - read the current value | |
| 41 | output[01] - sets the output value | |
| 42 | direction[01] - direction of each bit: 1=input, 0=output | |
| 43 | invert[01] - toggle the input bit sense | |
| 44 | ||
| 45 | input reads the actual state of the line and is always available. | |
| 46 | The direction defaults to input for all channels. | |
| 47 | ||
| 48 | ||
| 49 | General Remarks | |
| 50 | --------------- | |
| 51 | ||
| 52 | Note that each output, direction, and invert entry controls 8 lines. | |
| 53 | You should use the read, modify, write sequence. | |
| 54 | For example. to set output bit 0 of 1. | |
| 55 | val=$(cat output0) | |
| 56 | val=$(( $val | 1 )) | |
| 57 | echo $val > output0 | |
| 58 |