Help Using Counter to Flash LED In a Set it And Forget it Fashion

Juliet Oscar Echo

I need help getting an LED to flash at 2 Hz in a set it and forget it fashion. I don't want to use a cog just to flash an LED. I know there's got to be a way to do it using a single counter, but so far no joy.

The following is from the Counter Modules and Circuit Applications Lab in the Propeller Education Kit Labs: Fundamentals. It will flash an LED connected to pin 12, but because of the "repeat" command, it's not a set it and forget it use for the counter.

I also tried looking on the OBEX and previous posts, but all the LED flashing applications I came across had way too many bells and whistles. All I need is a simple on / off.

I know this is very basic. Any help would be much appreciated.


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
CON

_clkmode = xtal1 + pll16x
_xinfreq = 5_000_000


PUB Start_Flash_Alarm | tc, tHa, t

ctra[30..26] := 100
ctra[5..0] := 12
frqa := 1
dira [12]~~

tC := clkfreq
tHa := clkfreq/4
t := cnt

repeat
phsa := -tHa
t += tC
waitcnt(t)

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Ariba

Here is a simple code that does what you want:

CON
 _clkmode = xtal1 + pll16x 
 _xinfreq = 5_000_000 

PUB Start_Flash_Alarm 

 ctra[30..26] := %00100  'NCO mode
 ctra[5..0] := 12        'LED pin
 frqa := 107             '= 2^32 / clkfreq * 2

 repeat
   dira[12] := 1         'flashing  for 3 s
   waitcnt(clkfreq*3+cnt)
   dira[12] := 0         'not flashing for 3 s
   waitcnt(clkfreq*3+cnt)

It also shows how you can enable and disable the flashing.

Andy

Juliet Oscar Echo

Works Perfect. Thanks Andy.

Mark_T

This thread is also pertinent I think: http://forums.parallax.com/showthread.php/143483-Make-an-LED-pulse-%28smoothly-go-on-and-off%29-without-any-code-interaction?highlight=LED+fading