1======================= 2Kernel driver w1_ds2413 3======================= 4 5Supported chips: 6 7 * Maxim DS2413 1-Wire Dual Channel Addressable Switch 8 9supported family codes: 10 11 ================ ==== 12 W1_FAMILY_DS2413 0x3A 13 ================ ==== 14 15Author: Mariusz Bialonczyk <manio@skyboo.net> 16 17Description 18----------- 19 20The DS2413 chip has two open-drain outputs (PIO A and PIO B). 21Support is provided through the sysfs files "output" and "state". 22 23Reading state 24------------- 25The "state" file provides one-byte value which is in the same format as for 26the chip PIO_ACCESS_READ command (refer the datasheet for details): 27 28======== ============================================================= 29Bit 0: PIOA Pin State 30Bit 1: PIOA Output Latch State 31Bit 2: PIOB Pin State 32Bit 3: PIOB Output Latch State 33Bit 4-7: Complement of Bit 3 to Bit 0 (verified by the kernel module) 34======== ============================================================= 35 36This file is readonly. 37 38Writing output 39-------------- 40You can set the PIO pins using the "output" file. 41It is writable, you can write one-byte value to this sysfs file. 42Similarly the byte format is the same as for the PIO_ACCESS_WRITE command: 43 44======== ====================================== 45Bit 0: PIOA 46Bit 1: PIOB 47Bit 2-7: No matter (driver will set it to "1"s) 48======== ====================================== 49 50 51The chip has some kind of basic protection against transmission errors. 52When reading the state, there is a four complement bits. 53The driver is checking this complement, and when it is wrong then it is 54returning I/O error. 55 56When writing output, the master must repeat the PIO Output Data byte in 57its inverted form and it is waiting for a confirmation. 58If the write is unsuccessful for three times, the write also returns 59I/O error. 60