freebsd-dev/usr.sbin/pwm/pwm.8

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.\" Copyright (c) 2018 Emmanuel Vadot <manu@freebsd.org>
.\"
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.\" modification, are permitted provided that the following conditions
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
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.\" $FreeBSD$
.\"
.Dd June 17, 2019
.Dt PWM 8
.Os
.Sh NAME
.Nm pwm
.Nd configure PWM (Pulse Width Modulation) hardware
.Sh SYNOPSIS
.Nm
.Op Fl f Ar device
.Fl C
.Nm
.Op Fl f Ar device
.Op Fl D | Fl E
.Op Fl p Ar period
.Op Fl d Ar duty
.Sh DESCRIPTION
The
.Nm
utility can be used to configure pwm hardware.
.Nm
uses a
.Xr pwmc 4
device to communicate with the hardware.
Some PWM hardware supports multiple output channels within a single
controller block; each
.Xr pwmc 4
instance controls a single PWM channel.
.Pp
.Xr pwmc 4
devices are named
.Pa /dev/pwm/pwmcX.Y ,
where
.Va X
is the controller unit number and
.Va Y
is the channel number within that unit.
.Pp
The options are as follows:
.Bl -tag -width "-f device"
.It Fl f Ar device
Device to operate on.
If not specified,
.Pa /dev/pwm/pwmc0.0
is used.
If an unqualified name is provided,
.Pa /dev/pwm
is automatically prepended.
.It Fl C
Show the configuration of the PWM channel.
.It Fl D
Disable the PWM channel.
.It Fl d Ar duty
Configure the duty cycle (in nanoseconds or percentage) of the PWM channel.
Duty is the portion of the
.Ar period
during which the signal is asserted.
.It Fl E
Enable the PWM channel.
.It Fl p Ar period
Configure the period (in nanoseconds) of the PWM channel.
.El
.Sh EXAMPLES
.Bl -bullet
.It
Show the configuration of the PWM channel:
.Bd -literal
pwm -f /dev/pwm/pwmc0.1 -C
.Ed
.It
Configure a 50000 ns period and a 25000 ns duty cycle
and enable the channel:
.Bd -literal
pwm -f pwmc1.1 -E -p 50000 -d 25000
.Ed
.It
Configure a 50% duty cycle on the device and channel which
were configured in
.Xr pwmc 4
to have the label
.Pa backlight :
.Bd -literal
pwm -f backlight -d 50%
.Ed
.El
.Sh SEE ALSO
.Xr pwm 9 ,
.Xr pwmbus 9
.Sh HISTORY
The
.Nm
utility appeared in
.Fx 13.0 .
.Sh AUTHORS
.An -nosplit
The
.Nm
utility and this manual page were written by
.An Emmanuel Vadot Aq Mt manu@FreeBSD.org .