Kernel driver w1_ds2413¶
- Maxim DS2413 1-Wire Dual Channel Addressable Switch
supported family codes:
Author: Mariusz Bialonczyk <firstname.lastname@example.org>
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 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.