Subject:
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Re: Possible bug? Simple light sensor condition checking.
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Newsgroups:
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lugnet.robotics.rcx.legos
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Date:
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Mon, 16 Jul 2007 17:14:42 GMT
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Viewed:
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16043 times
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> At 11:13 AM 7/16/07, Timothy Su wrote:
> > I tried my own skill on writing a program for the included lego test pad (RIS
> > 2.0), and I discovered something weird. The following code does set the
> > conditions right, but the following code doesn't set the conditions right if I
> > comment out the 'cputs("");'. Any idea why?
It looks to me like the c compiler optimized the assignment to the
variable away, since there is no external method call
(shutdown_requested() is just a macro).
> >
> > int offonpad =0;
You should make this
volatile int offonpad = 0;
> > while(!shutdown_requested()) {
> > if(LIGHT(LIGHTSENS) < 40) {
> > offonpad = 1;
> > }
> > else {
> > offonpad = 0;
> > }
> > //cputs("");
> > }
You should also put an msleep(10) or at least a yield() somewhere
inside the loop; otherwise it uses up its full time-slice without
letting any other thread react to the change of the variable. You can
tweak the sleep time to balance between reaction time and cpu usage.
Regards,
Jochen
--
Jochen Hoenicke,
Email: hoenicke@informatik.uni-freiburg.de
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