Button as a toggle

A lever stays where you put it. A button (StructureLogicButton) springs back. Still, you often want a button to switch the light on and, with the next press, off again, like a light switch in a corridor.

What the button reports#

When you press the button, Activate jumps to 1. After a little more than half a second the game resets it to 0 by itself. So a press is a short pulse, and the chip sees it for one or two ticks. While the pulse runs, the button accepts no new press.

The naive attempt#

lbn button BUTTON HASH("Lichttaster") Activate Average
xor light light button     # toggle on 1

This toggles in every tick in which Activate is 1. If the chip sees the pulse for two ticks, it switches on and straight off again. The light seems to react at random.

Edge instead of a steady signal#

Only the rising edge should toggle, that is the one tick in which the button goes from 0 to 1:

sgt edge button last       # just pressed?
move last button
xor light light edge       # toggle on the edge only
sbn LAMP HASH("Flurlicht") On light

xor with 1 flips the state, xor with 0 leaves it alone. That is exactly what a toggle needs.

Debouncing with a lockout#

Real push buttons bounce: the contact rattles and delivers several edges in a row. The button in the game does not bounce, but players like to press twice in quick succession. A short lockout after every toggle catches that:

slez ready lock            # lockout over?
and edge edge ready
xor light light edge
sub lock lock 1
select lock edge LOCKOUT lock
max lock lock 0

After a toggle lock holds LOCKOUT and counts down by 1 every tick. Only at 0 does the next edge count again.