if the button is wired to ground, other side to teensy pin, yes, one pin. suggest you put a 220-330 ohm series resistor always to protect the pin.
in your code its as simple as:
Setting the pin to work with your button:
pinMode(pin, INPUT_PULLUP);
Then checking the state in your loop:
if ( digitalReadFast(pin) == 0 ) {
//button pushed, do something
delay(10);
}
of course, since your planning to push and possibly hold the button, you'd have to adjust your code to compensate for it...
while ( digitalReadFast(pin) == 0 ) {
while ( digitalReadFast(pin) == 0 ); //wait here until you let go
//button pushed, do something
delay(10);
}
then theres always possibilities for long hold does something different than a quick press
endless possibilities, but those interests deserve their own posts