On 6 Apr 2003 at 11:21, Jinx wrote:

> I made up a number of F628 circuits that have been installed (not by
> me) in small planes, and all seemed to be well until a couple of the
> pilots reported back that, when using the radio, now and then the PICs
> acted as though one of the circuit switches had been operated. The
> symptoms indicate that noise is getting into at least Portb4 and being
> interpreted as a switch closure. I've not yet been able to get to the
> either of the circuits to physically check how they've been installed,
> mainly because they're overseas. It couldn't have been the ones just
> up the road that went funny could it !!

Double check how your software reads this input. You may have it
already, but a switch debounce kind of routine where the input state
(high or low) must be stable for say, at least 10ms before accepting
it. The assumption is that when the RF interference is present the
input state may be oscillating. A software fix can be a whole lot
faster to install in the field than adding lots of hardware filter
components.

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Brent Brown, Electronic Design Solutions
16 English Street, Hamilton, New Zealand
Ph/fax: +64 7 849 0069
Mobile/txt: 025 334 069
eMail:  brent.brown@clear.net.nz

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