Entirely reasonable. Pull-downs are better if using pins that have=20 TTL thresholds (as opposed to Schmitt Trigger thresholds) - the=20 nominal logic HI threshold with 5V power supply is about 1.3Vdc. Personally, I'd be using 10k pull-downs and 1k or 2k2 series=20 resistors for the switches. Even if you use high-value series=20 resistors like 2k2, the voltage at the PIC pin is well above 3.5V=20 (assuming 5V rail) which gives very good noise immunity. Note that some newer PICs have Schmitt Trigger inputs on some=20 ports. Those are more difficult to deal with - you want to be within=20 10% of either Gnd or Vdd for your logic input levels. Even so, 10k=20 pull-down and 1k series resistors works well. dwayne At 10:58 AM 5/13/2013, Justin Richards wrote: >Just wanted to run this past the wisdom of the list. > >Port Pins RA4 - RA7 on a 16F887 are successfully driving a standard 2 x 16 >LCD (via a shift >register). > >Want to add 4 push buttons (ENTER, EXIT, UP,DOWN). > >Possible solution > >use weak pull downs approx 4.7K from port pin to ground. > >use 680ohm from port pin to N/O push button then to +V. > >PIC should still be able to drive pins high or low as needed to control LC= D >even when switch is pressed. Quick test seems to indicate this is ok. > >Current when PIN driven low and switch is pressed, I =3D V/R =3D 5/680 ~ 7= mA >(+ LCD and shift reg loading) > >Is this plausible. > >Cheers Justin >-- >http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive >View/change your membership options at >http://mailman.mit.edu/mailman/listinfo/piclist --=20 Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax www.trinity-electronics.com Custom Electronics Design and Manufacturing --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .