Contents
Once you’ve got a pushbutton working, you often want to do some action based on how many times the button is pushed. To do this, you need to know when the button changes state from off to on, and count how many times this change of state happens. This is called state change detection or edge detection.
How long does a button press take?
Moreover, a button press is very fast, occurring within 100 milliseconds, and is too fast for correcting movement. The key to understanding button-pressing is therefore to understand how the brain adapts based on the limited sensations that are the residue of the brief press event.
As the standard, 40 ligne or 40L equals 1 inch or 25 milimiters. So 1L equals 0.635mm. To calculate button size in ligne, simply divide the diameter of the button (in millimeters) by 0.635.
Can a system detect if a push button was pressed?
Your system can’t be doing anything else at all while you’re waiting on the button. That may be fine for some situations, but far from ideal for 99% of others. It is better to remember the state of the button and detect that change of state. Personally, to make it properly portable, I would implement a class to contain all the state information.
You could use a timer variable (based on this example from their docs) to save the exact time when you pressed or released the button, so you can check the difference between both variables to calculate how long it is on hold or idle. The code should look something like this:
How do I keep track of the push button?
Second, a simple state-machine is needed to keep track of the button state but also if the return button action function, doReturnButton (), has already been called. The button is assumed to be connected from GND to pin4.
Both are only called once per push (transition high to low). To avoid the multiple transitions that occur when a button is pushed a debounce time period is used. The can also be done in hardware with a RC-circuit. This also demonstrates the callback on the release of the button.