I notice the ADC input sensitivity changes radically when the PC serial programming cable is plugged in or out. Also, the ADC input goes a little negative for a few milliseconds when READADC is executed. I see this with pins and command READADC 0 or 1 or 2.
The input to READADC 0 is a photo diode and works perfect on a PICAXE08 proto board running the same circuits and nearly the same program code.
My 5V source is a well filtered lab supply with short leads.
Whats this about adding a BAT85 Schottky diode to the Serial Input line??? Is this the answer to this problem???
Thanks … Bill