piclist 2000\11\04\152730a >
Thread: keypad scan problem
face BY : Ethan Swint email (remove spam text)


I'm currently taking a class where we use a pic emulator (Tech Tools
ClearView Mathias using a PIC1674A) and a C compiler.  Our program was to
read inputs from the keypad on port b and output it to a PC via RS232 on
port c.  The program didn't work - unless our digital scope was hooked up to
the keypad inputs on port b!  We ran across something in the documentation
that described an input pullup resistor, but setting this option didn't seem
to have any effect.  My best guess is that there was some capacitance in the
keypad that prevented the signals from switching properly and the scope
provided a path to ground for the inputs.  You might try hooking up large
external resistors to the keypad.

I've attatched the list file (can be viewed in text editor) in that shows
the C code with the assembly for anyone who's interested.

Ethan Swint

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See also: www.piclist.com/techref/microchip/devices.htm?key=pic
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