On Tue, Mar 26, 2002 at 04:39:35PM -0000, Gary wrote:
> Hi,
>
> I am having a problem with waking my 16F628 from SLEEP, I want it to wake up when the button is pressed, in other words RB0 is now at 0V. I have set the PIC to wake up on the falling edge, does this mean that when the button is at 0V = PIC now awake?, as this is how I understand it?
>

No. It mans that the pin must go from a high state to a low state in order to
trigger. Your circuit below will generate such a falling edge.

> Problem= If long cables are used for the switch, it picks up noise and the software thinks the button has been pressed!
>

Two possible solutions there. First is to use a stronger pullup resistor.
Second is to add another resistor and  a capacitor into the circuit to
that the line cannot instanteaneously change. That way noise will be
filtered. Something like this:


   +5
    |
   R1
    |
    +---R2---+-----RB0
    |        |
    S        C
    |        |
    +----+---+
         |
        GND

Make sure that R2 is much smaller than R1 so that when the switch is pressed
that the voltage divider will output a low voltage. For example if R1=10k
and R2=100 then the output voltage will be 50mV which should be low enough
to trigger the interrupt.

> The problem is that I cannot find away of debouncing the button, as the way I have it configured, it will not Wake Up until the button is pressed AND released, the exact opposite of what I want.
>

Well that's sounds like a rising edge. BTW the above circuit will help with
debounce also.

> I want it to wake on Button down AND wait X milli seconds, then check it is still at 0V, the code I have written, is below, and the button connections, any ideas where I am going wrong?
>

No clue. But I bet that cleaning up the noise will help significantly.

BAJ

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