interupt pull up, is it possible?

Hi Guys, new to all this so maybe a stupid question, please forgive me.

I want to use a hall digital device to generate interupts, I have it all working but would like to know how to set up interupt on a uno with the internal pull up resistor. Do I assign the pin as an input pullup then assign it as an interupt or is it just not possible?

Yes, pinMode to INPUT_PULLUP and that will turn on the pull up resistor. Then attach your interrupt. Attaching the interrupt doesn't affect your pinMode at all.

Many thanks, thats what I thought

You didn't think to just try it?

Is the hall sensor remote? If so you might want a stronger pull-up than the on-chip pullups which are quoted as between 20k and 50k in the datasheet.

Sure no problem trying it but it seems to work without defining it as an input at all so I guess its just drifting high enough to switch, the pullup I guess will turn it high with some "force" and hence be more reliable.

Good point re the remote but it should be a compact unit maybe worst case 50mm of flying leeds, I will have a play with some longer leads to see if its an issue thanks.

MarkT: You didn't think to just try it?

In a case like this, that might not be a good idea. Just because something works, doesn't necessarily mean that it works well. It's better to determine the limits of the system and try to stay away from them.