I am looking for a little help from somebody that has experience connecting a matrix style keypad to the Keyboard IF on the AT89C51.

I have a 4x4 matrix style keypad and I am not quite sure the proper method of connecting, debouncing and scanning for keypresses. My best assumption is to debounce the 4 row pins and connect them to the keyboard interrupts on Port1. Then I would leave the other 4 column pins bouncy and connect them to regular inputs. Upon interupt I would scan the inputs to see which key was pressed....

Is there a better method of interfacing with the keypad?

Hello

You can use 4 bit of a port like port1 for 4 lines you pull alternately one after the other, and use the remaining 4 bit of the port1 with activated interrupt to scan the column. You can do the debounce with a timer activated in the keyboard interrupt routine.


Best regards
Michel Passemard
Atmel 8051 Technical Support

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I wonder if I can leave the lines going into the interrupt bouncy?

this is a 4 x 4 interface with code. The code is in C and it includes debouncing.

I can't remember where I got this.
I hope this helps.

Do you prefer assembler?
Did you use the search function of this forum? I presume not because if you did, you find this one
4x4 key pad programing - please help
with HW description and assembler code...
Good luck

Originally Posted by mcs51mc

Do you prefer assembler?
Did you use the search function of this forum? I presume not because if you did, you find this one
4x4 key pad programing - please help
with HW description and assembler code...
Good luck

mcs51mc I saw that post and was just wondering what assembler to use for these sources. Is it A51.exe? IF so where to download? Any links?

Thanks

and you can download it from http://www.ustr.net/files/download.shtml

Have fun...

I've worked with this assembler. it is so clean . produces 2 files .lst file and the hex file. the simulator also i found it very very useful, though it is a demo version i used to seperate the codes into blocks and will execute it. Hence i recommend you all this assembler and simulator. the later is dos based but that's really fun with few keys as input.

Regards,
maha

Dear All
Can anybody tell me to interface LCD 16pin (2 pin for back light) with AT89c2051 which is receiving serial data from pc and will display accordingly.
Pls do urgent....i will be too much gratefull ..