| ======================= |
| 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. |
