Help 4x4 Keypad interfacing using Parallel Port in Turbo C++

[Harsh.Realm]

turbo c++ parallel port

I need help I'm trying to interface a 4x4 keypad with a parallel port using Turbo C++.

+--+--+--+--+
| 1 | 2 | 3 | A |
+--+--+--+--+
| 4 | 5 | 6 | B |
+--+--+--+--+
| 7 | 8 | 9 | C |
+--+--+--+--+
| 0 | F | E | D |
+--+--+--+--+

I have D0-D3 (outport)connected to the rows pins 1-4 and S3-S6(inport) connected to the columns pins 5-8. Where do I go from here?

If anyone can help me out, it would be greatly appreciated.

Thanks

 

[jhbbunch]

interfacing a keypad in the pc parallel port

Hook 4 output pins to the columns and four input pins to the rows. Put 10K pullups on the input lines. Use a loop to set each of the output line low, with the other 3 output pins high. Then check each input line. If one is a logic low you have a keypress for that column and row.
If you use pulldowns (resistors to ground) then the logic is reversed. Set each output pin high with the other output pins set low and loop through the 4 input lines. If you find one that is a logic high then you have a keypress for that row and column.

You will need a parallel port .dll that allows access to reading and writing to ports if you are using WinXP. There are several on the internet.

 

[yogi]

keypad 4x4+parallel port

see the links below
**broken link removed**
**broken link removed**


Bibin John
www.bibinjohn.tk