LED(4) FreeBSD Kernel Interfaces Manual LED(4)
NAME
led - API for manipulating LED's, lamps and other annunciators
SYNOPSIS
#include <dev/led/led.h>
typedef void led_t(void *priv, int onoff);
struct cdev *
led_create_state(led_t *func, void *priv, char const *name, int state);
struct cdev *
led_create(led_t *func, void *priv, char const *name);
void
led_destroy(struct cdev *);
DESCRIPTION
The led driver provides generic support for handling LEDs, lamps and
other annunciators.
The hardware driver must supply a function to turn the annunciator on and
off and the device name of the annunciator relative to /dev/led/. The
priv argument is passed back to this on/off function and can be used
however the hardware driver sees fit.
The lamp can be controlled by opening and writing ASCII strings to the
/dev/led/bla device.
In the following, we will use this special notation to indicate the
resulting output of the annunciator:
* The annunciator is on for 1/10th second.
_ The annunciator is off for 1/10th second.
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.
0 Turn the annunciator off immediately.
1 Turn the annunciator on immediately.
Flashing can be set with a given period. The pattern continues
endlessly.
f _*
f1 _*
f2 __**
f3 ___***
...
f9 _________*********
Three high-level commands are available:
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.
s%s String. This gives full control over the annunciator.
Letters `A' ... `J' turn the annunciator on for from 1/10th
to one full second. Letters `a' ... `j' turn the
annunciator off for 1/10th to one full second. Letters `u'
and `U' turn the annunciator off and on respectively when
the next UTC second starts. Unless terminated with a `.',
the sequence is immediately repeated.
m%s Morse.
`.' becomes `_*'
`-' becomes `_***'
` ' becomes `__'
`\n' becomes `____'
The sequence is repeated after a one second pause.
FILES
/dev/led/*
EXAMPLES
A `d12' flashes the lamp
*__________*_*______________________________
A `sAaAbBa' flashes
*_*__**_
/usr/bin/morse -l "Soekris rocks" > /dev/led/error
SEE ALSO
morse(6)
HISTORY
The led driver first appeared in FreeBSD 5.2.
AUTHORS
This software was written by Poul-Henning Kamp <
[email protected]>.
This manual page was written by Sergey A. Osokin <
[email protected]> and
Poul-Henning Kamp <
[email protected]>.
FreeBSD 14.1-RELEASE-p8 April 24, 2007 FreeBSD 14.1-RELEASE-p8