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