INT_RB and edge detection

aodj · Joined: 20 Dec 2006 Posts: 40 Location: Reading, UK

I'm currently using the port B interrupt, INT_RB, to detect when a button is pushed. However, since the interrupt is enabled on both high to low and low to high transitions, for one button press, I get two interrupts.

Does anyone know of a way to make this interrupt only return with one of these edge transitions?

Foppie · Joined: 16 Sep 2005 Posts: 138 Location: The Netherlands

try using:

aodj · Joined: 20 Dec 2006 Posts: 40 Location: Reading, UK

I thought that only applied to the INT_EXT interrupt?

Foppie · Joined: 16 Sep 2005 Posts: 138 Location: The Netherlands

asmallri · Joined: 12 Aug 2004 Posts: 1635 Location: Perth, Australia

Ttelmah · Guest

As has already been said, you can't. However there might be another alternative. As well as the normal INT_EXT, you can use the CCP module as a 'cheating' way of getting another external interrupt if this is not already being used. Basically you program this in 'compare' mode, to interrupt on one 'count', and since the interrupt can be set to operate on the CCP pin being high, or low, you can generate the effect of another external interrupt pin!...

Best Wishes

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

CCS has an example file that shows how to use push buttons with the
#int_rb interrupt. It gives the option of compiling it to detect a low-to-high
transition or a high-to-low transition. Here's the file location: