Kernel driver w1_ds2413 ======================= Supported chips: * Maxim DS2413 1-Wire Dual Channel Addressable Switch supported family codes: W1_FAMILY_DS2413 0x3A Author: Mariusz Bialonczyk 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.