freebsd-dev/share/man/man4/owc.4
Warner Losh ae1f3df434 New 1-Wire bus implementation. 1-Wire controller is abstracted, though
only gpiobus configured via FDT is supported. Bus enumeration is
supported. Devices are created for each device found. 1-Wire
temperature controllers are supported, but other drivers could be
written. Temperatures are polled and reported via a sysctl.  Errors
are reported via sysctl counters. Mis-wired bus detection is included
for more trouble shooting. See ow(4), owc(4) and ow_temp(4) for
details of what's supported and known issues.

This has been tested on Raspberry Pi-B, Pi2 and Beagle Bone Black
with up to 7 devices.

Differential Revision: https://reviews.freebsd.org/D2956
Relnotes: yes
MFC after: 2 weeks
Reviewed by: loos@ (with many insightful comments)
2015-08-27 23:33:38 +00:00

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2.7 KiB
Groff

.\"
.\" Copyright (c) 2015 M. Warner Losh
.\" All rights reserved.
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.\" modification, are permitted provided that the following conditions
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" $FreeBSD$
.\"
.Dd July 20, 2015
.Dt OWC 4
.Os
.Sh NAME
.Nm owc
.Nd Dallas Semiconductor 1-Wire Controller
.Sh SYNOPSIS
.Cd device owc
.Sh DESCRIPTION
The
.Nm
module implements Dallas Semiconductor 1-Wire signaling.
It attaches the
.Xr ow 4
driver 1-Wire bus protocol.
The
.Nm
device implements the Link Layer of the 1-Wire bus protocol stack.
.Pp
Bit banging a pin on a
.Xr gpiobus 4
is the only supported controller.
Both standard and overdrive transfer timings are implemented.
Strong pull-up functionality needed to support parasitic mode is not
implemented.
.Pp
To enable 1-Wire for FDT systems requires modifying the DTS for your
board to add something like:
.Bd -literal
/ {
...
onewire {
compatible = "w1-gpio";
gpios = <&gpio 4 1>;
};
...
};
.Ed
.Pp
The gpios property describes the GPIO pin the 1-Wire bus is connected
to.
For more details about the
.Va gpios
property, please consult
.Pa /usr/src/sys/boot/fdt/dts/bindings-gpio.txt .
.Sh SEE ALSO
.Xr gpiobus 4 ,
.Xr ow 4 ,
.Xr ow_temp 4 ,
.Xr owll 9 ,
.Xr own 9
.Sh LEGAL
.Tn 1-Wire
is a registered trademark of Maxim Integrated Products, Inc.
.Sh HISTORY
The
.Nm
driver first appeared in
.Fx 11.0 .
.Sh AUTHORS
The
.Nm
device driver and this manual page were written by
.An Warner Losh .
.Sh CAVEATS
The gpio driver implements timing by busy waiting, which can cause a
high load on slower systems.
.Sh BUGS
Overdrive mode has not actually been tested.