Keypad input - Extra Circuitry

ZapWizard · Post by **ZapWizard** » Wed Mar 16, 2005 11:18 am

I want to utilize my LK202-24-USB-GW keypad interface to it's upmost potential.

But my project will be using touch-sensative buttons.
These are driven by QTouch IC's. www.Qprox.com
The IC's can output either Active High or Active Low.

How can I interface these into the matrix keypad inputs?

More specificly, how does the LCD poll the keypad?
Would it be possible to wire a transistor between a column and row, and connect the base to my sensor?

I only need two actual key inputs.

Tom · Post by **Tom** » Wed Mar 16, 2005 11:55 am

Hi ZapWizard,

Thank you for posting at the forums.

Just to give you a better idea if it is possible to interface the touch sensitive buttons, I will tell you how the keypad interface works on the Matrix Orbital units work. When a key is pressed, a row and a column is physically shorted together, and the short will be detected by the pic. The firmware inside the pic goes through a scanning algorithm, and detects which row and column is shorted. The pic will then send a character on the RX line. If you can figure out how to short the row and column together, you can get your touch-sensative button to work.

The characters are shown in section 3.2 of the manual at http://www.matrixorbital.com/files/LK202-24-USB_02.pdf .

I hope this helps you on your project.

Best Regards,

ZapWizard · Post by **ZapWizard** » Wed Mar 16, 2005 12:10 pm

Thanks for the super fast response.

I will have to do some experimenting then.
It sounds like a transitor may work.
Worst case I need to find some very small relays.

Also I think I will also wire two of my hard-wired buttons into the display, that way I can have the LCD display and event to go along with the button.

Here if the design for the project:
http://www.zapwizard.com/Projects/wood/ ... 11-big.jpg

The buttons are:
Power -Hardwired, Turns system on, windows programmed to ignore it once booted.
DVD Eject -Hardwired, but with the LCD I could put a "Eject DVD" display.
IDE -Wired to LCD, when pressed it would display harddrive stats.
WIFI -Wired to LCD, when pressed it would display network stats.

I will also have two LEDs running off the GPO, they will light up a E-Mail, and CPU 100% load indicators next to the display. (Black area on rendering)

Tom · Post by **Tom** » Wed Mar 16, 2005 1:02 pm

Wow your case looks pretty cool.

If you have anymore pictures, you can post them in the gallery.

Good luck with your project.

If you have anymore questions or concerns, please feel free to post.

Best Regards,

ZapWizard · Post by **ZapWizard** » Wed Mar 16, 2005 9:44 pm

I found some SIP REED relays that will be tiny and perfect to run the keypad.
------
Am I correct that the High Power GPO's can PWM LEDs without extra circuitry?
(Due to a firmware upgrade)

I would like to use the PWM output to run three seperate banks of LEDs.
Each bank will have around 24 LEDs total.

Post by **Henry** » Wed Mar 16, 2005 11:15 pm

Hey ZapWizard,

Thanks for dropping by our corner of the world... The high power GPO's are not current limited, and output over an amp each. The will PWM and you will probaby have to change the base frequency as well.