.\" Copyright (c) 2003 Sergey A. Osokin <osa@FreeBSD.org>
.\" All rights reserved.
.\"
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.\" modification, are permitted provided that the following conditions
.\" are met:
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.\" $FreeBSD: head/share/man/man4/led.4 278616 2015-02-12 05:35:00Z cperciva $
.\"
.Dd April 24, 2007
.Dt LED 4
.Os
.Sh NAME
.Nm led
.Nd API for manipulating LED's, lamps and other annunciators
.Sh SYNOPSIS
.In dev/led/led.h
.Pp
.Fd "typedef void led_t(void *priv, int onoff);"
.Ft struct cdev *
.Fn led_create_state "led_t *func" "void *priv" "char const *name" "int state"
.Ft struct cdev *
.Fn led_create "led_t *func" "void *priv" "char const *name"
.Ft void
.Fn led_destroy "struct cdev *"
.Sh DESCRIPTION
The
.Nm
driver provides generic support for handling LEDs, lamps and other
annunciators.
.Pp
The hardware driver must supply a function to turn the annunciator on and off
and the device
.Fa name
of the annunciator relative to
.Pa /dev/led/ .
The
.Fa priv
argument is passed back to this on/off function and can be used however
the hardware driver sees fit.
.Pp
The lamp can be controlled by opening and writing
.Tn ASCII
strings to the
.Pa /dev/led/bla
device.
.Pp
In the following, we will use this special notation to indicate the resulting
output of the annunciator:
.Pp
.Bl -tag -width indent -offset indent -compact
.It Ic *
The annunciator is on for 1/10th second.
.It Ic _
The annunciator is off for 1/10th second.
.El
.Pp
State can be set directly, and since the change happens immediately,
it is possible to flash the annunciator with very short periods and
synchronize it with program events.
It should be noted that there is a non-trivial overhead, so this may
not be usable for benchmarking or measuring short intervals.
.Pp
.Bl -tag -width indent -offset indent -compact
.It Ic 0
Turn the annunciator off immediately.
.It Ic 1
Turn the annunciator on immediately.
.El
.Pp
Flashing can be set with a given period.
The pattern continues endlessly.
.Pp
.Bl -tag -width indent -offset indent -compact
.It Ic f
_*
.It Ic f1
_*
.It Ic f2
__**
.It Ic f3
___***
.It ...
.It Ic f9
_________*********
.El
.Pp
Three high-level commands are available:
.Bl -tag -width indent -offset indent
.It Ic d%d
Numbers.
Each digit is blinked out at 1/10th second, zero as ten pulses.
Between digits a one second pause and after the last
digit a two second pause after which the sequence is repeated.
.It Ic s%s
String.
This gives full control over the annunciator.
Letters
.Ql A
.No ...
.Ql J
turn the annunciator on for from 1/10th to one full
second.
Letters
.Ql a
.No ...
.Ql j
turn the annunciator off for 1/10th
to one full second.
Letters
.Ql u
and
.Ql U
turn the annunciator off and on respectively when the next
UTC second starts.
Unless terminated with a
.Ql \&. ,
the sequence is immediately repeated.
.It Ic m%s
Morse.
.Pp
.Bl -tag -width indent -offset indent -compact
.It Ql \&.
becomes
.Ql _*
.It Ql -
becomes
.Sq Li _***
.It Ql "\ "
becomes
.Sq Li __
.It Ql \en
becomes
.Sq Li ____
.El
.El
.Pp
The sequence is repeated after a one second pause.
.Sh FILES
.Bl -tag -width ".Pa /dev/led/*"
.It Pa /dev/led/*
.El
.Sh EXAMPLES
A
.Sq Li d12
flashes the lamp
.Pp
.Dl *__________*_*______________________________
.Pp
A
.Sq Li sAaAbBa
flashes
.Pp
.Dl *_*__**_
.Bd -literal
/usr/bin/morse -l "Soekris rocks" > /dev/led/error
.Ed
.Sh SEE ALSO
.Xr morse 6
.Sh HISTORY
The
.Nm
driver first appeared in
.Fx 5.2 .
.Sh AUTHORS
.An -nosplit
This software was written by
.An Poul-Henning Kamp Aq Mt phk@FreeBSD.org .
.Pp
This manual page was written by
.An Sergey A. Osokin Aq Mt osa@FreeBSD.org
and
.An Poul-Henning Kamp Aq Mt phk@FreeBSD.org .