Documentation/w1/slaves/w1_ds2413.rst
Supported chips:
supported family codes:
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W1_FAMILY_DS2413 0x3A
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Author: Mariusz Bialonczyk [email protected]
The DS2413 chip has two open-drain outputs (PIO A and PIO B). Support is provided through the sysfs files "output" and "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.
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.