Based on kernel version 6.13
. Page generated on 2025-01-21 08:21 EST
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 | .. SPDX-License-Identifier: GPL-2.0-or-later ===================== Kernel driver w1-uart ===================== Author: Christoph Winklhofer <cj.winklhofer@gmail.com> Description ----------- UART 1-Wire bus driver. The driver utilizes the UART interface via the Serial Device Bus to create the 1-Wire timing patterns as described in the document `"Using a UART to Implement a 1-Wire Bus Master"`_. .. _"Using a UART to Implement a 1-Wire Bus Master": https://www.analog.com/en/technical-articles/using-a-uart-to-implement-a-1wire-bus-master.html In short, the UART peripheral must support full-duplex and operate in open-drain mode. The timing patterns are generated by a specific combination of baud-rate and transmitted byte, which corresponds to a 1-Wire read bit, write bit or reset pulse. For instance the timing pattern for a 1-Wire reset and presence detect uses the baud-rate 9600, i.e. 104.2 us per bit. The transmitted byte 0xf0 over UART (least significant bit first, start-bit low) sets the reset low time for 1-Wire to 521 us. A present 1-Wire device changes the received byte by pulling the line low, which is used by the driver to evaluate the result of the 1-Wire operation. Similar for a 1-Wire read bit or write bit, which uses the baud-rate 115200, i.e. 8.7 us per bit. The transmitted byte 0x80 is used for a Write-0 operation (low time 69.6us) and the byte 0xff for Read-0, Read-1 and Write-1 (low time 8.7us). The default baud-rate for reset and presence detection is 9600 and for a 1-Wire read or write operation 115200. In case the actual baud-rate is different from the requested one, the transmitted byte is adapted to generate the 1-Wire timing patterns. Usage ----- Specify the UART 1-wire bus in the device tree by adding the single child onewire to the serial node (e.g. uart0). For example: :: @uart0 { ... onewire { compatible = "w1-uart"; }; }; |