RE: Re: Rabbit 2000

["Paul Smith" <ukha@xxxxxxxxxxxxx>]

>
> Pretty unlikely I think - much more likely to be caused by dirty/noisy
> power rails. Try decoupling the power rails around your pulse counting
> circuitry using 100nF caps. If you have access to a scope you make
> also want to look at the shape of the conditioned pulses that you are
> counting - you may need to add a schmidt trigger or similar to prevent
> false triggers if the leading or trailing edge is rising slowly (and
> you should be edge triggering, not level triggering, in this kind of
> application).
>
> Cheers
> Patrick

Hi Patrick,

Thanks for the heads up, I have two screen shots from before an after
fitting the caps'

http://www.ptu.biz/Before.jpg

http://www.ptu.biz/after.jpg

Which shows (C1) the pulse from the transistor and C2 the pulse going into
rabbit. The transistor is connected to a 555 monostable circuit.

The rabbit has a timerb isr running at
200uSec this is the code from it:

nodebug root void TimerBRoutine()
{
if (BitRdPortI(PBDR, 3))
{
vs1=0;
}
else
{
if (vs1==0)
{
c1++;
p1d=MS_TIMER - p1t;
p1t=MS_TIMER;

}
vs1=1;
}
if (BitRdPortI(PBDR, 2))
{
vs2=0;
}
else
{
if (vs2==0)
{
c2++;
}
vs2=1;
}
last_mstimer=MS_TIMER;
}


How do I tell rabbit to look for an edge rather than a level as I guess I
am doing that the mo.

Regards,

Paul



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