Quote Originally Posted by RFEFX View Post
Porta.4 which is an Schmitt trigger input reads the low voltage just fine...
I would expect more trouble with the Schmitt trigger which requires 0.8*Vdd or 4V for logic high.

Anyway, I usually use the circuits shown in FIG 13 or FIG 14 in this App Note http://www.zbasic.net/appNotes/AN213.pdf