Keypad does not work if LCD is not connected

kushb · Joined: 21 Sep 2005 Posts: 7

Hi,

I am using the ACE kit of CCS. My circuit involves displaying digits on PC screen using keypad. I have been able to do it succesfully. The only problem is that keypad does not function if a LCD display is not connected at port D. The moment LCD display is disconnected from port D the keypad stops responsing. Can anyone explain me why is this happening and what could be the possible solution.

Thanks

Mark · Joined: 07 Sep 2003 Posts: 2838 Location: Atlanta, GA

Are you still trying to initialize the LCD?

Guest · Posted: Mon Oct 10, 2005 10:50 am

Mark,

No I am not initializing LCD.

Mark · Joined: 07 Sep 2003 Posts: 2838 Location: Atlanta, GA

Is the keypad on port D as well?
Are there pullups on the keypad lines?

kushb · Joined: 21 Sep 2005 Posts: 7

Yeah the keypad is on port D.
By pullup do you mean that I should connect the data lines of port D with a pull up resistor??

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

Yes, put the pull-up resistors on the keypad row pins.
http://www.ccsinfo.com/forum/viewtopic.php?t=24443

Guest · Posted: Fri Oct 14, 2005 11:42 am

i had the same problem before this ACE kit board uses pull up resistors only on port B , if you want to use the keypad on port D u should put the LCD with it too , cuase it acts as a pull ups for PORT D

if u noticed in the KBD.c it says something like this connect pull up to the specfic port or LCD

hope this helps

thanks