[SOLVED] simple interfacing of 4x3 keypad

[eeHassan]

Hey,
I want to interface a simple 4x3 keypad with 89c51....how can i do that without using any encoder?

 

[horace1]

if you have 7 spare digitial IO lines you connect the 3 columns and 4 rows and decode the key presses in software. If you search the forum you should find plenty of examples of circuits and code.

 

[eeHassan]

okay..........

 

[Medtronic]

I think this will be helpful for you

Matrix Keypad interfacing with Microcontroller AVR tutorial: AVR Programming : 8051 Microcontroller Projects AVR PIC Projects Tutorials Ebooks Libraries codes

MedTronic

 

[Medtronic]

This is a very useful Microcontroller Interfacing Techniques file

Best Regards

MedTronic

 

[ckshivaram]

check this
Matrix Keypad interfacing with Microcontrollers tutorial: : 8051 Microcontroller Projects AVR PIC Projects Tutorials Ebooks Libraries codes
Projects | uC Microcontroller Interfacing & Decoding Matrix Keyboard

 

[andre_luis]

Check out this implementation :


#define LINES 0x0F
#define ROWS 0xF0

unsigned char ScanKey ( void )
{
unsigned char ReadingKey = 0 ;

MicrocontrollerOutput = LINES;
Delay(4) ;
ReadingKey = (~( MicrocontrollerOutput | ROWS )) ;
if ( ReadingKey )
{
MicrocontrollerOutput = ROWS ;
Delay(4) ;
ReadingKey += (~( MicrocontrollerOutput | LINES )) ;
return ( ReadingKey ) ;
}
else return ( NO_KEY ) ;
}

Note that Low nible pins of port read High pins of port and vice-versa.

The constraint are :
1 ) keyboard pins of uC must be at an entyre port ( i.e.: P3 )
2 ) Doesn´t work by interrupt.

The big advantage is :
You can map a wide combintions of simultaneous pins pressed ( like CTRL or SHIFT function )

+++

 

[sherazi]

8051 keypad interface -