logic for a mobile keypad

[engg.embedded]

mobile keypad with 8051

hi...

im working on a project in which one part is to interface a 4x4 hex keypad with 8051. i hv done that interfacing bt the problem is i want to multiplex a single key.
i.e.
if i press 1 on the keypad a 1 gets displayed on the LCD, if i press 2 a 2 gets displayed, and like wise for other keys also. Bt my problem is as i press 1 a 1 should get displayed bt if within 1 sec if i again press 1 some character like '@' should get displayed and then if again within 1 sec i press 1 some other character like '&' should get displayed. And if after 1 sec i press 1 the process should start from all over again. Its almost similar to what we do while we type a message on a mobile phone.
Im not getting the logic for this. If anyone could help, will be really thankful.

 

[nandhu015]

mobile keypad

where is the code?

without the code no one can answer your question

Nandhu

 

[engg.embedded]

i hv tried many permutations and combinations for the program to work, bt still not the desired output.
im uploading one of the programs that i hv written. i knw its wrong and im nt gttng the actual logic. plz help on this program basis.
also rite now im nt takng into consideration the other keys.
Im jus taking the first key. i guess if i can make the first key to work according to my desire, i can make others to work in the same way.

 

[daya_260]

i m looking for the same but , i implemented PS/2 protocol, the keypad is connected to normal PC and tried , there is delay in the key out in the computer

Is there logic for the keypad to make as mobile keypad

 

[Golden Electronics]

Please implement Ur logic correctly in truth table of in steps with key no. & required action only for first key condtion

 

[daya_260]

Please implement Ur logic correctly in truth table of in steps with key no. & required action only for first key condtion

I ve written code for keypad scanning and then Ps/2 protocol connect it to PC

I m using counter along with timer (software) even i m facing problem delay and some uncertainty in the function