back-panel LED control device derived from code by der Mouse

1 files changed, 59 insertions, 0 deletions

diff --git a/share/man/man4/man4.sun3/leds.4 b/share/man/man4/man4.sun3/leds.4
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+.\"	$OpenBSD: leds.4,v 1.1 1997/01/13 00:29:27 kstailey Exp $
+.\"
+.Dd March 2, 1996
+.Dt LEDS 4 sun3
+.Os OpenBSD 2.0
+.Sh NAME
+.Nm leds
+.Nd back-panel LEDs
+.Sh DESCRIPTION
+The file
+.Nm /dev/leds
+is an interface to the diagnostic array of 8 light-emitting diodes on
+the back of the computer.
+.Pp
+This file contains two
+.Sy unsigned int Ns s
+(in native byte order, as would be written by passing the address of an
+.Sy unsigned int
+to
+.Xr write 2 ,
+which on a Sun-3 means big-endian), followed by a string of bytes.  The
+string of bytes gives the successive patterns to be displayed on the
+LEDs; each byte's bits are taken and used to drive the LEDs.  A 0 bit
+illuminates the corresponding LED; a 1 bit leaves the corresponding LED
+dark.  The first
+.Sy unsigned int
+gives the number of clock ticks that are skipped after each pattern is
+loaded before the next is loaded.  For example, if this value is 0, a
+new pattern is loaded each clock tick; if it is 3, a new pattern will
+be loaded every fourth clock tick (ie, three ticks will be skipped
+between loads).  The second
+.Sy unsigned int
+gives the number of patterns in the list, that is, the number of bytes
+following the two
+.Sy unsigned int Ns s.
+.Pp
+There are limits on the two integer values; attempting a write that
+would cause either of them to take on too large a value causes the
+write to return EIO without affecting anything.  The limits are
+compiled into the kernel; as of this writing, the first one can be at
+most 128, the second at most 10240.
+.Sh EXAMPLES
+This example displays a single lit LED scrolling from one end of the
+display to the other, over and over, moving every six clock ticks.  The
+first eight bytes supply the two
+.Sy unsigned int Ns s
+mentioned above; the other eight specify the patterns.  (Convert them
+to binary, and remember that 0 bits mean lit LEDs.)
+.Bd -ragged -offset -ident
+# echo 0 0 0 5 0 0 0 8 254 253 250 247 239 223 175 127 |
+  awk '{ for (i=1;i<=NF;i++) printf("%c",$i+0); }' > /dev/leds
+.Ed
+.Sh FILES
+.Bl -tag -width /dev/leds -compact
+.It Pa /dev/leds
+.El
+.Sh HISTORY
+.Nm /dev/leds
+appeared in post-2.0 OpenBSD.