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.