Mark, I did this with a 20x4 LCD and it worked great, check out my code at http://www.ultranet.com/~jason I put the 4 buttons at each corner of the display and you put up a message to their function depending on what you want when... Kinda like an ATM machine.... Jason -----Original Message----- From: Mark Birks To: PICLIST@MITVMA.MIT.EDU Date: Wednesday, October 29, 1997 12:04 PM Subject: A stupid question but... >Is it possible to multiplex the scanning of 4 push-button switches on >the same 4 'data' lines as an LCD module is using ? > >I've sort of thought along the lines of having all of the switches >commoned at one side and then having an OPen -collector arrangement to >short the switches to ground at read time. > >The drawback with this arrangement is that when the switches are NOT >being read and one or more switches are closed, data lines will be >shorted together. Adding diodes seemed like an obvious step forward but >the 0.7V drop takes them to the top end of the TTL logic '0' level. > >Anyone got any suggestions please ? > >Also I am looking at using a standard 16x2 LCD with these switches to >allow menu selection and configuration settings - has anyone done >anything that allows the PIC to communicate with a host processor (in >this case it is ACORN podule bus) to download menu choices, selections >etc. I am trying to reduce the amount of processing done by the host so >that the PIC can deal with most of the menu control if poss........ > > \\\|/// > \\ - - // "Yes it IS safe > ( @ @ ) to switch on" >+---oOOo-(_)-oOOo------------------+ >| Mark Birks | >| Hardware Section Leader | >| OmniBus Systems, Stanford House, | >| Stanford-on-Soar, | >| Loughborough, Leicestershire. UK.| >| | >| Tel/Fax: +44 (0)990 004300/333 | >| E-Mail: markb@omnibus.co.uk | >| ooo0 | >| ( ) 0ooo | >+---\ (----( )------------------+ > \_) ) / > (_/ >