Hi Jinx.

> > > Are there any floating inputs, by accident or oversight ?
> > There is one floating input.............
> > Leaving an input floating can fry the chip?
> http://www.piclist.com/techref/logic/xtrapins.htm
> The author says (about a floating input) -
> "The power loss due to rapid switching of a tri-stated input pin
> may be significant. Disclamer: I do not have hard data on this,
> but I believe I'm correct. Rapid switching will not fry the chip"

I believe that rumors about switching tri stated pin will cause chip
damage are complete nonsense. Floating pins are proved to cause
extensive current sonsumption ( in battery application power saving
modes ) but not to extend frying the chip out.

I rather check with scope if electrolytic capacitor in power adapter
has dried out and power adapter is out of specs or pulsating above
the +5 power specs. Output pin shortages to +5 power or ground is
seconds thing to check.


> Noise (eg ripple) coming from the PSU "probably" won't do
> any harm, but spikes, especially sub-0V, coming from other
> sources into pins can fatally damage a PIC. The reason
> is that the internal diode conducts and the pin's circuitry burns
> out. The cure for this is to protect the internal diode with an
> external Schottky diode, which will conduct before the internal
> one and so shunt the spike away

I would recomend to place small resistor i.e. 200 OHm is series
with PIC inputs connected to outside 0 to 5V signals to limit ingoing
current to prevent that possibility in most situations ( for higher
possible input voltages resistor should be increased ) After all if
ESD is an issue ( all mystical deaths when winter time is approaching )
ESD protection elements should be used on the board entrances.


WBR Dmitry.
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