Documentation/w1/slaves/w1_ds2413.rst

Source file repositories/reference/linux-study-clean/Documentation/w1/slaves/w1_ds2413.rst

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Linux kernel
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Documentation/w1/slaves/w1_ds2413.rst
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Support Tooling And Documentation
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Documentation
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Support Tooling And Documentation: documentation
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Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

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Annotated Snippet

=======================
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.

Annotation

Implementation Notes