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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W1_FAMILY_DS2413 0x3A
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Author: Mariusz Bialonczyk <manio@skyboo.net>
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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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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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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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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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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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