Need some help for my vhdl project (with keypad, LED and LCD)

[zorro3k]

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[TrickyDicky]

Draw the whole circuit on paper, before you write any VHDL.

 

[lucbra]

think about what you want to do with your keypad (ok these are the inputs). Now try to decode the inputs from the 4x4 keypad so that you can do something meaningful with it (decode de numbers, '*' and '#')

Have you figured out how you will select to enter a password? How will your password look like?

The next thing is to let something appear on your LCD (just a simple character in first, later some static text, afterwards text that depends on a keypress)..

If you get that far, you will have figured ou how to continue

Good luck with your first steps in VHDL

 

[zorro3k]

because i'm a beginner, i'll make it as simple as possible. I don't use keypad encoder, i suppose that i'll receive 4 bit data from the keypad which is the position of the pressed key, am i supposed to use a lookup table to recognize the key? How can i know the entered password is right or wrong (the password contains 3 decimal number) ? Can you give me some sample code?
To display text on the LCD needs 8 bits data, right? What are these 8 bits? (for example, i wanna display "H").

 

[lucbra]

It's not the encoder that you'll need, it's a decoder (isn't that what I wrote).

You can use a lookup table to do that job, but don't forget to debounce your keypad.

Depending on the strength of your encryption - you can make it as simple or as difficult as you like.

In the beginning, I would start with comparing the password with a preprogrammed register (during configuration). But start with decoding your keypad, that's a good point to start with the basics of VHDL.

Have you considered taking some sort of course, or take a book about VHDL (there are numerous examples in this forum of good books to start with)?

If you don't understand the basics of the language, you won't get very far.

With respect to the LCD - you will need the datasheet of it. Most LCDs can operate in 4-bit and 8-bit mode.

Of course I can give examples - I could even do the job for you, but that's not the point. You asked for basic help how to start - not that someone made the design for you, did you?

 

[zorro3k]

Can u give me some simple examples so that i can understand how it work ( just principle, not the detail, similar but not the same ). Thanks you very much, lucbra. You make a good point.

 

[lucbra]

Can u give me some simple examples so that i can understand how it work ( just principle, not the detail, similar but not the same ). Thanks you very much, lucbra. You make a good point.

Just browse through the forum, you will find LCD controller, keypad decoder, state machines for other tasks ...

https://www.edaboard.com/threads/211053/ for the LCD controller

https://www.edaboard.com/threads/210749/ : keypad controller

https://www.edaboard.com/threads/210619/ : debouncing a switch

Of course you will need to do something more to glue it together. Just copying the code won't give you the solution

 

[zorro3k]

You don't get me at all, lucbra. In this project, I don't intent to use either keypad encoder or debounce. Anyway, thanks for your help.

 

[lucbra]

Fine

Good luck!

 

[mrflibble]

You don't get me at all, lucbra. In this project, I don't intent to use either keypad encoder or debounce. Anyway, thanks for your help.

Translation: You don't intend to follow the hints that people try to give you to help you prevent beginners mistakes.

Tip: please do use a debounce, because otherwise you will spend a lot of time trying to figure out why things don't work the way you expected it. If you don't know what debounce is , google. But don't just dismiss it...

Also, by going over a bit of the functionality you mention ... password entry, validation, display stuff on lcd based on this ... I would suggest using a softcore mcu like a picoblaze. You are free to choose to not do this and use a statemachine. In which case, double good luck.