🚀 go-pugleaf

In article <92315.190637DI3QC@CUNYVM.BITNET> <DI3QC@CUNYVM.BITNET> writes:
>     I am planning to interface a keypad to the io lines of an hc11. Does anyon
>e have any suggestions on connecting a keypad. I was planning to scan the keypa
>d by driving one of the rows hi and testing the columns. I was planning on test
>ing this every 20ms. How would I take care of debouncing etc. Any suggestions.

I have come up with several solutions. Use a telephone key pad it fits on a 
single port and much more elegant solution is to connect resistors
across the key pad and using it for a voltage divider, saw this in Electronics
& wireless  World. Hook up the key pad with the resister and put a resistor
in series with the  key pad v+ and v-. Hook one of the pins of port 
E (watch out putting it on E0 if you are using BUFFALO it jumps to EEPROM
if E is high. and do an  A/D  and find the key board data using a single port.

A good deal of  thought is required to figure out the resistor net work. 
Diodes might be need to prevent unwanted current paths.

Hope this helps,
Gordon

AB5Dg   Agriculture Engineering Oklahoma State University
gcouger@olesun.agen.okstate.edu 405-744-6514 day 744-2794 evenings