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/games/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 ⟨phk@FreeBSD.org⟩.
This manual page was written by
Sergey A.
Osokin ⟨osa@FreeBSD.org⟩ and
Poul-Henning Kamp
⟨phk@FreeBSD.org⟩.