114 lines
3.1 KiB
Groff
114 lines
3.1 KiB
Groff
.\"
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.\" Copyright (c) 2015 M. Warner Losh
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. The name of the author may not be used to endorse or promote products
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.\" derived from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd June 26, 2019
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.Dt OWC 4
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.Os
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.Sh NAME
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.Nm owc
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.Nd Dallas Semiconductor 1-Wire Controller
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.Sh SYNOPSIS
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.Cd device owc
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.Sh DESCRIPTION
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The
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.Nm
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module implements Dallas Semiconductor 1-Wire signaling.
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It attaches the
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.Xr ow 4
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driver 1-Wire bus protocol.
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The
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.Nm
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device implements the Link Layer of the 1-Wire bus protocol stack.
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.Pp
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Bit banging a pin on a
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.Xr gpiobus 4
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is the only supported controller.
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Both standard and overdrive transfer timings are implemented.
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Strong pull-up functionality needed to support parasitic mode is not
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implemented.
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.Pp
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To enable 1-Wire for FDT systems requires modifying the DTS for your
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board to add something like:
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.Bd -literal
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/ {
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...
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onewire {
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compatible = "w1-gpio";
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gpios = <&gpio 4 1>;
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};
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...
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};
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.Ed
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.Pp
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The gpios property describes the GPIO pin the 1-Wire bus is connected
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to.
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For more details about the
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.Va gpios
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property, please consult
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.Pa /usr/src/sys/dts/bindings-gpio.txt .
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.Pp
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On a
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.Xr device.hints 5
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based system these values are required for the
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.Nm :
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.Bl -tag -width ".Va hint.owc.%d.atXXX"
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.It Va hint.owc.%d.at
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The
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.Nm gpiobus
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you are attaching to.
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.It Va hint.owc.%d.pins
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This is a bitmask that defines a pin on the
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.Nm gpiobus
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that is to be used for the 1-Wire bus.
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For instance, to configure pin 10, use the bitmask of 0x400.
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Please note that this mask should have only one bit set
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(any other bits - i.e., pins - will be ignored).
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.El
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.Sh SEE ALSO
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.Xr gpiobus 4 ,
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.Xr ow 4 ,
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.Xr ow_temp 4 ,
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.Xr owll 9 ,
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.Xr own 9
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.Sh LEGAL
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.Tn 1-Wire
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is a registered trademark of Maxim Integrated Products, Inc.
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.Sh HISTORY
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The
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.Nm
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driver first appeared in
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.Fx 11.0 .
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.Sh AUTHORS
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The
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.Nm
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device driver and this manual page were written by
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.An Warner Losh .
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.Sh CAVEATS
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The gpio driver implements timing by busy waiting, which can cause a
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high load on slower systems.
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.Sh BUGS
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Overdrive mode has not actually been tested.
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