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59 lines
1.8 KiB
59 lines
1.8 KiB
======================= |
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Kernel driver w1_ds2413 |
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======================= |
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Supported chips: |
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* Maxim DS2413 1-Wire Dual Channel Addressable Switch |
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supported family codes: |
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================ ==== |
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W1_FAMILY_DS2413 0x3A |
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================ ==== |
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Author: Mariusz Bialonczyk <[email protected]> |
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Description |
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----------- |
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The DS2413 chip has two open-drain outputs (PIO A and PIO B). |
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Support is provided through the sysfs files "output" and "state". |
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Reading state |
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------------- |
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The "state" file provides one-byte value which is in the same format as for |
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the chip PIO_ACCESS_READ command (refer the datasheet for details): |
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======== ============================================================= |
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Bit 0: PIOA Pin State |
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Bit 1: PIOA Output Latch State |
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Bit 2: PIOB Pin State |
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Bit 3: PIOB Output Latch State |
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Bit 4-7: Complement of Bit 3 to Bit 0 (verified by the kernel module) |
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======== ============================================================= |
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This file is readonly. |
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Writing output |
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-------------- |
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You can set the PIO pins using the "output" file. |
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It is writable, you can write one-byte value to this sysfs file. |
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Similarly the byte format is the same as for the PIO_ACCESS_WRITE command: |
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======== ====================================== |
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Bit 0: PIOA |
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Bit 1: PIOB |
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Bit 2-7: No matter (driver will set it to "1"s) |
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======== ====================================== |
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The chip has some kind of basic protection against transmission errors. |
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When reading the state, there is a four complement bits. |
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The driver is checking this complement, and when it is wrong then it is |
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returning I/O error. |
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When writing output, the master must repeat the PIO Output Data byte in |
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its inverted form and it is waiting for a confirmation. |
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If the write is unsuccessful for three times, the write also returns |
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I/O error.
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