| bgardner@wabtec.com | 69dd204 | 2005-06-07 08:55:38 -0500 | [diff] [blame] | 1 | Kernel driver pca9539 |
| 2 | ===================== |
| 3 | |
| 4 | Supported chips: |
| 5 | * Philips PCA9539 |
| 6 | Prefix: 'pca9539' |
| 7 | Addresses scanned: 0x74 - 0x77 |
| 8 | Datasheet: |
| 9 | http://www.semiconductors.philips.com/acrobat/datasheets/PCA9539_2.pdf |
| 10 | |
| 11 | Author: Ben Gardner <bgardner@wabtec.com> |
| 12 | |
| 13 | |
| 14 | Description |
| 15 | ----------- |
| 16 | |
| 17 | The Philips PCA9539 is a 16 bit low power I/O device. |
| 18 | All 16 lines can be individually configured as an input or output. |
| 19 | The input sense can also be inverted. |
| 20 | The 16 lines are split between two bytes. |
| 21 | |
| 22 | |
| 23 | Sysfs entries |
| 24 | ------------- |
| 25 | |
| 26 | Each is a byte that maps to the 8 I/O bits. |
| 27 | A '0' suffix is for bits 0-7, while '1' is for bits 8-15. |
| 28 | |
| 29 | input[01] - read the current value |
| 30 | output[01] - sets the output value |
| 31 | direction[01] - direction of each bit: 1=input, 0=output |
| 32 | invert[01] - toggle the input bit sense |
| 33 | |
| 34 | input reads the actual state of the line and is always available. |
| 35 | The direction defaults to input for all channels. |
| 36 | |
| 37 | |
| 38 | General Remarks |
| 39 | --------------- |
| 40 | |
| 41 | Note that each output, direction, and invert entry controls 8 lines. |
| 42 | You should use the read, modify, write sequence. |
| 43 | For example. to set output bit 0 of 1. |
| 44 | val=$(cat output0) |
| 45 | val=$(( $val | 1 )) |
| 46 | echo $val > output0 |
| 47 | |