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     led -- API for manipulating LED's, lamps and other annunciators


     #include <dev/led/led.h>

     typedef void led_t(void *priv, int onoff);

     led_create(led_t *func, void *priv, char const *name);

     led_destroy(dev_t dev);


     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 how-
     ever 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 synchro-
     nize 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 end-

	   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.

			 `.'	 becomes `_*'
			 `-'	 becomes `_***'
			 ` '	 becomes `__'
			 `\n'	 becomes `____'

     The sequence is repeated after a one second pause.


     A `d12' flashes the lamp


     A `sAaAbBa' flashes


     /usr/games/morse -l "Soekris rocks" > /dev/led/error






     The led driver first appeared in FreeBSD 5.2.


     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>.

FreeBSD 5.4		       November 3, 2003 		   FreeBSD 5.4


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