linux-stable/Documentation/w1/slaves/w1_ds2413.rst
Mauro Carvalho Chehab e9bb627561 docs: w1: convert to ReST and add to the kAPI group of docs
The 1wire documentation was written with w1 developers in
mind, so, it makes sense to add it together with the driver-api
set.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2019-07-31 14:16:17 -06:00

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ReStructuredText

=======================
Kernel driver w1_ds2413
=======================
Supported chips:
* Maxim DS2413 1-Wire Dual Channel Addressable Switch
supported family codes:
================ ====
W1_FAMILY_DS2413 0x3A
================ ====
Author: Mariusz Bialonczyk <manio@skyboo.net>
Description
-----------
The DS2413 chip has two open-drain outputs (PIO A and PIO B).
Support is provided through the sysfs files "output" and "state".
Reading state
-------------
The "state" file provides one-byte value which is in the same format as for
the chip PIO_ACCESS_READ command (refer the datasheet for details):
======== =============================================================
Bit 0: PIOA Pin State
Bit 1: PIOA Output Latch State
Bit 2: PIOB Pin State
Bit 3: PIOB Output Latch State
Bit 4-7: Complement of Bit 3 to Bit 0 (verified by the kernel module)
======== =============================================================
This file is readonly.
Writing output
--------------
You can set the PIO pins using the "output" file.
It is writable, you can write one-byte value to this sysfs file.
Similarly the byte format is the same as for the PIO_ACCESS_WRITE command:
======== ======================================
Bit 0: PIOA
Bit 1: PIOB
Bit 2-7: No matter (driver will set it to "1"s)
======== ======================================
The chip has some kind of basic protection against transmission errors.
When reading the state, there is a four complement bits.
The driver is checking this complement, and when it is wrong then it is
returning I/O error.
When writing output, the master must repeat the PIO Output Data byte in
its inverted form and it is waiting for a confirmation.
If the write is unsuccessful for three times, the write also returns
I/O error.