xref: /freebsd/share/man/man4/owc.4 (revision fa9896e082a1046ff4fbc75fcba4d18d1f2efc19)

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.Dd June 26, 2019
.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/dts/bindings-gpio.txt .
.Pp
On a
.Xr device.hints 5
based system these values are required for the
.Nm :
.Bl -tag -width ".Va hint.owc.%d.atXXX"
.It Va hint.owc.%d.at
The
.Nm gpiobus
you are attaching to.
.It Va hint.owc.%d.pins
This is a bitmask that defines a pin on the
.Nm gpiobus
that is to be used for the 1-Wire bus.
For instance, to configure pin 10, use the bitmask of 0x400.
Please note that this mask should have only one bit set
(any other bits - i.e., pins - will be ignored).
.El
.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.