1Kernel driver w1_ds2413
2=======================
3
4Supported chips:
5  * Maxim DS2413 1-Wire Dual Channel Addressable Switch
6
7supported family codes:
8        W1_FAMILY_DS2413        0x3A
9
10Author: Mariusz Bialonczyk <manio@skyboo.net>
11
12Description
13-----------
14
15The DS2413 chip has two open-drain outputs (PIO A and PIO B).
16Support is provided through the sysfs files "output" and "state".
17
18Reading state
19-------------
20The "state" file provides one-byte value which is in the same format as for
21the chip PIO_ACCESS_READ command (refer the datasheet for details):
22
23Bit 0:   PIOA Pin State
24Bit 1:   PIOA Output Latch State
25Bit 2:   PIOB Pin State
26Bit 3:   PIOB Output Latch State
27Bit 4-7: Complement of Bit 3 to Bit 0 (verified by the kernel module)
28
29This file is readonly.
30
31Writing output
32--------------
33You can set the PIO pins using the "output" file.
34It is writable, you can write one-byte value to this sysfs file.
35Similarly the byte format is the same as for the PIO_ACCESS_WRITE command:
36
37Bit 0:   PIOA
38Bit 1:   PIOB
39Bit 2-7: No matter (driver will set it to "1"s)
40
41
42The chip has some kind of basic protection against transmission errors.
43When reading the state, there is a four complement bits.
44The driver is checking this complement, and when it is wrong then it is
45returning I/O error.
46
47When writing output, the master must repeat the PIO Output Data byte in
48its inverted form and it is waiting for a confirmation.
49If the write is unsuccessful for three times, the write also returns
50I/O error.
51