implementing diode keyboard matrix

Christophe · Joined: 10 May 2005 Posts: 323 Location: Belgium

Hi,

I want to implement a 9 x 8 keyboard matrix (72 keys) with some diodes for simultaneous keypress detection. So I will have rows and columns. How does the algorithm works? Are the Rows outputs and the columns inputs? Are there any examples?

http://www.sensotec.be/ASP/Catalog.asp?ID=Sensotec%20EUROSCOPE&LC=10 You can see the device with the buttons..

newguy · Joined: 24 Jun 2004 Posts: 1903

http://www.ccsinfo.com/forum/viewtopic.php?t=19726

This will give you an idea of how to start.

Christophe · Joined: 10 May 2005 Posts: 323 Location: Belgium

He's using portB interrupts.. I cannot use that code because I have 9 rows x 8 columns

newguy · Joined: 24 Jun 2004 Posts: 1903

Right. I didn't say that you could use that code as is, only that it would help give you ideas about what to do. Now that you see how it's done with 16 buttons, couldn't you "scale" that approach to get your 72 buttons?

treitmey · Joined: 23 Jan 2004 Posts: 1094 Location: Appleton,WI USA

Christophe · Joined: 10 May 2005 Posts: 323 Location: Belgium

Well the matrix can be divided into 3 matrices:

* 3R x 8C matrix : simultaneous press detection needed
* 1 x 8 matrix : simultaneous
* 5 x 8 matrix: only single press detection needed

treitmey · Joined: 23 Jan 2004 Posts: 1094 Location: Appleton,WI USA

Christophe · Joined: 10 May 2005 Posts: 323 Location: Belgium

Of course that is possible..

set row '1'

read 8 column bits

=> decode bits to keypresses

treitmey · Joined: 23 Jan 2004 Posts: 1094 Location: Appleton,WI USA

Sory, I guess you have this solved.

Guest · Posted: Mon May 16, 2005 1:48 pm

I mean it is possible without extra IC's ... with a pic only and diodes.. I'm just asking for some tips/code samples , algorithms, something that can get me started...