Interrupts

dehan · Joined: 28 Jun 2012 Posts: 1

I want to increment a counter, when an external push button connected to my pic ic 16f877a is pressed. I am quite new to interrupts and have no idea on how they work. Can you give me a very basic coding with line by line explanation of how this is done.

temtronic · Posted: Thu Jun 28, 2012 1:40 pm

There are several example programs that CCS kindly supplies in the examples folder.Some of those do use interrupts and have the information you need to complete your project.
I'm quite busy at my other job, organic farming, and cannot afford to spend the time to cut the code you want, unless you can wait for 3 weeks.You'ld also have to supply the crystal you're using as well as which pin the interrrupt will occour on.PB7...4 or PB0 would be the obvious choices.
Now if you want to come here and tear apart a 60 year old tractor and fix it, I'll cut the code while you fix my problem .
Seems fair to me.
hth jay

Mike Walne · Joined: 19 Feb 2004 Posts: 1785 Location: Boston Spa UK

Nice one Jay.

No, seriously he's right, this a help forum, NOT a do it for you.

Show us that you have tried and we will gladly assist.

It's useful for you to read the CCS forum guide.

Mike

Ttelmah · Joined: 11 Mar 2010 Posts: 19369

Also, there may be severe "doubt's" about whether an interrupt on the button is the right solution. Buttons tend to _bounce_. When pushed, you can often get several connection pulses one after the other. Using an interrupt, you will count every one. Hence better in general, for something as slow as a button, to use a 'tick' timer, and verify that once the button is made, it is still made a few uSec latter, and only then 'accept' it. There is keyboard code, in the code library, which demonstrates 'debouncing'.

Best Wishes

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

Here is an older demo program for External Interrupts and it does have
an explanation of each line of code. It's at the end of the thread:
http://www.ccsinfo.com/forum/viewtopic.php?t=17301

This post gives an outline description of how to increment a variable
when a button is pushed, without actually giving the main code to do it:
http://www.ccsinfo.com/forum/viewtopic.php?t=44229&start=1
This code doesn't use interrupts.