Hello,

I was learning PIC BASIC language along with assembly, then I came up to a project which requires inputs of external keypad and the aim is to change the state of a particular port when 4 subsequent inputs of the keypad matches with the programmed.

In short, a lock system with 4 number password. Also in the project it asks to "inform" whether or the numbers pressed were correct or not.

Do you have any suggestions? I just have got blank trying to think how to make the computer realize that certain number matches certain bits.

Please help me on this one!

Thank you

 

Hi doodyman (hope you're not Arabic?!).

It helps to draw out a flowchart, in a paint program or just on paper. This lets you create a procedure, simple and neat, without code writing getting in the way and confusing you. Once you know exactly what the proedure is, writing the code gets easy.

Maybe a procedure a bit like this (psuedo code);

if(new key is received)
{
  //first move previous inputs down
  d = c
  c = b
  b = a
  // add in new key
  a = new_key
  // test for a match
  if(a=='h' && b=='e' && c=='l' && d=='p') openlock()
}

your flowchart procedure might also include a timeout period, or safety lockout after a bad 4digit code is entered etc.

 

I just have got blank trying to think how to make the computer realize that certain number matches certain bits.

I think that means being stuck on the actual keypad scan routine
(ie looking at bits on ports),
but there are so many tutorials dealing with interfacing a pic with a keypad,
I don't think it could be made any easier.