I'm programming a Leonardo to send keyboard keystrokes at the push of a button. I'm wiring it in the same way as pictured here;
My question is, if I'm wiring multiple buttons can I use just one 100k ohm pull-down resistor on the ground wire daisy-chain (towards the micro-controller's header)? I can, right?
Why use any? Use the internal pullup instead, and have each button connect its pin to Gnd.
in void setup:
pinMode (pinX, INPUT_PULLUP);
in void loop:
if (digitalRead(pinX) == LOW){
// take some action
}
I was still getting interference.
Interference from what? Each switch should only connect to a single pin on one side, and Gnd on the other.
When the button is open, nothing is connected except the Gnds.
Great, thanks!
My question is, if I'm wiring multiple buttons can I use just one 100k ohm pull-down resistor on the ground wire daisy-chain (towards the micro-controller's header)? I can, right?
And my answer is still: Use the internal pullup (available on each pin) instead, and have each button connect its pin to Gnd.
I will never endorse using a pulldown resistor and using the switch to connect the pin to +5.
mikejkelley:
My question is, if I'm wiring multiple buttons can I use just one 100k ohm pull-down resistor on the ground wire daisy-chain (towards the micro-controller's header)? I can, right?
No! Each input needs it's own pull-up or pull-down. When you press the button (and short the input to 5V) the pull-down resistor gets "overpowered" and is no longer "pulling-down"... That's the whole idea of how it works... The resistor provides enough current to pull-up (or down) the input when the switch is open. But, when the switch is closed, it "overpowers" the resistor and forces the input down (or up).
And, all of your inputs would have to be wired together at a common point, so pressing one button would affect all of the inputs.
No, your inputs would all be tied to the non-ground end of the pull-down resistor. When it gets pulled down by one button press, it will pull down all the other outputs it is tied/shorted/daisy-chained to.
Get your head around inpurs and pull p and pull down by reading this:-
http://www.thebox.myzen.co.uk/Tutorial/Inputs.html
And as others have said, no you can't just use one pull down.
Well you can but all the inputs will go high when ever you press any one of the many buttons.
Ok, thnx, yeah thru experimentation I found that just one pull-down resistor was not viable. Not sure that I've my head around it yet, but right now I just need a clear, straight path to functionality and I have that now, thanks again.