Re: [avr-gcc-list] external interrupt use

[Carlos Becker]

On Mon, 23 Feb 2004 18:59:01 -0800
Jamie Morken <address@hidden> wrote:

> Hi all,
> 
> I have 6 digital signals that I need to be able to trigger an interrupt on
> the falling edge and rising edge for all of them, but I am short 2 external
> interrupts.  Is there a simple way to detect the 6 signals rising/falling
> edges with 4 interrupts and some additional circuitry?  I have thought about
> using diodes to AND some of the signals but this only works for positive
> edges I think.
> 

It would work perfectly with some diodes, and using pullups better.

The question is how many falling/rising edges you want to detect 
"simultaneously".. I mean..

you have lines R1 and R2

only R0 generates rising/falling edge int..

you can use diodes to connect R1 and R2 to R0, but.. if a line is low then the 
other lines won't be able to put the pin of the avr high again, not to mention 
that it's already low..

I don't know if I explain myself clearly..
the circuit would be

R0 ---------
        D  D
        I  I
        O  O
        D  D
        E  E
        |  |
R1------   |
R2 ---------

so, only one line can pull it low at the same time so that R0 can realise if it 
was a falling edge.

_______________________________________________
avr-gcc-list mailing list
address@hidden
http://www.avr1.org/mailman/listinfo/avr-gcc-list