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- =======================
- Kernel driver w1_ds2413
- =======================
- Supported chips:
- * Maxim DS2413 1-Wire Dual Channel Addressable Switch
- supported family codes:
- ================ ====
- W1_FAMILY_DS2413 0x3A
- ================ ====
- Author: Mariusz Bialonczyk <[email protected]>
- 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.
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