At 06:34 PM 2/10/02 +0000, Dave Dilatush wrote: >Edson Brusque wrote... > > > Let's say no keys are pressed. You've charged all the caps with current > >passing through the diodes, then you havn't discharged any caps because no > >key are pressed when you turned RD4 LOW. Then you have RD7:RD4 as inputs > >reading LOW, because no current passes from the cap to the port by the keys. > >No current also passes through the (now reversed) diodes. > > > > How can this work? > >It doesn't. > >Darn it, I had pullup resistors on the port pins in this design when I >went to bed last night. But when I got up this morning I couldn't >remember what the heck I'd put them in there for. So I took them out. > >Now I know why they were there in the first place. > >Attached is the corrected design, with pullups included. > >Dave Close, except turn the diodes around. dwayne Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax Celebrating 18 years of Engineering Innovation (1984 - 2002) .-. .-. .-. .-. .-. .-. .-. .-. .-. .- `-' `-' `-' `-' `-' `-' `-' `-' `-' Do NOT send unsolicited commercial email to this email address. This message neither grants consent to receive unsolicited commercial email nor is intended to solicit commercial email. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.