1=======================
2Kernel driver w1_ds2413
3=======================
4
5Supported chips:
6
7  * Maxim DS2413 1-Wire Dual Channel Addressable Switch
8
9supported family codes:
10
11        ================        ====
12        W1_FAMILY_DS2413        0x3A
13        ================        ====
14
15Author: Mariusz Bialonczyk <manio@skyboo.net>
16
17Description
18-----------
19
20The DS2413 chip has two open-drain outputs (PIO A and PIO B).
21Support is provided through the sysfs files "output" and "state".
22
23Reading state
24-------------
25The "state" file provides one-byte value which is in the same format as for
26the chip PIO_ACCESS_READ command (refer the datasheet for details):
27
28======== =============================================================
29Bit 0:   PIOA Pin State
30Bit 1:   PIOA Output Latch State
31Bit 2:   PIOB Pin State
32Bit 3:   PIOB Output Latch State
33Bit 4-7: Complement of Bit 3 to Bit 0 (verified by the kernel module)
34======== =============================================================
35
36This file is readonly.
37
38Writing output
39--------------
40You can set the PIO pins using the "output" file.
41It is writable, you can write one-byte value to this sysfs file.
42Similarly the byte format is the same as for the PIO_ACCESS_WRITE command:
43
44======== ======================================
45Bit 0:   PIOA
46Bit 1:   PIOB
47Bit 2-7: No matter (driver will set it to "1"s)
48======== ======================================
49
50
51The chip has some kind of basic protection against transmission errors.
52When reading the state, there is a four complement bits.
53The driver is checking this complement, and when it is wrong then it is
54returning I/O error.
55
56When writing output, the master must repeat the PIO Output Data byte in
57its inverted form and it is waiting for a confirmation.
58If the write is unsuccessful for three times, the write also returns
59I/O error.
60