How to toggle button on and off with gpiozero?

Question

Abandoned post by Unregistered user.

I can't seem to find a solution of doing this using gpiozero. I've done it using rpi.gpio with add_event_detect and call back to change state but I was under the impression gpiozero is much simpler.

This link https://projects.raspberrypi.org/en/projects/physical-computing/9 basically says a switch would turn the led on with a pressed and release then turn is off with another pressed and release but doesn't actually show how to do this.

from gpio import LEDBoard, Button

button = Button(5, pull_up=True, bounce_time=200)
leds = LEDBoard(26, 19, 13, 6)

def on():
leds.on()
print('On...')

def off():
leds.off()
print('off...')

button.when_pressed = on
button.when_released = off

It doesn't even turn off when released. Is that due to the pull_up = True? I thought this code would turn it on when pressed and off when released but it just turns on and stays on.

TIA!

Answer 1

Question

How to toggle a button ... ?

Answer

Well, the OP's "question" is not a question，so I can give no answer. But I can explain why the OP's "question" is not a question.

1. A human can press a button and then release the button. This is not a "toggle". Let us say if the human presses button and then releases, and after some time, the human presses the button again and releases. Now there are two sequences of press event and release event, or if you like, one sequence of four events: press, release, press, release. No "toggling" happened ever.

2. Now the LED. Python can "toggle" a LED, ie, if the LED is on, then turn it off, and vice versa. This is the meaning of "toggling" a LED.

In other words, python can toggle a LED, but never a button, because only a human can change the status of a button: being pressed, being released. I know it is confusing. Perhaps a picture helps.

The picture below tells (1) how to toggle LED, and (2) how to read button.

Answer 2

Are you asking to have the LED on when the button is pressed and off when the button is unpressed? If so, this section from the gpiozero docs explains how to do so:

"Turn on an LED when a Button is pressed:

from gpiozero import LED, Button 
from signal import pause 

led = LED(17) 
button = Button(2)

button.when_pressed = led.on
button.when_released = led.off 

pause()

Alternatively:

from gpiozero import LED, Button 
from signal import pause 

led = LED(17) 
button = Button(2) 

led.source = button 

pause()

Answer 3

There is a toggle function in GPIO zero. So if you want a single LED on pin 26 to change state every time a button on pin 5 is pressed:

from gpiozero import LED, Button
from time import sleep

led = LED(26)
button = Button(5)

while True:
    if button.is_pressed:
        led.toggle()
        sleep(0.5)

(The sleep is needed, otherwise it changes state while you're pressing the button, and all you get is a strobing LED when you push the button)

Answer 4

I meant how do I turn a button into a switch?

from gpiozero import LED, Button

led = LED(25)
button = Button(2)

while True : # otherwise the script will only work once
        button.wait_for_press()
        led.toggle()
        button.wait_for_release()

So I need 2 sequences to turn it off and on

Example 1: toggle state with functions (stays on or off)

from gpiozero import LED, Button

led = LED(25) # GPIO 25
ledState= 0
button = Button(2) # GPIO 2

def on():
    led.on() # Since Python doesn't have function-enclosing parentheses, here are 4 spacebars to assign the contents to the function.

def off():
    led.off()


while True : # otherwise the script will only work once
        button.wait_for_press()
        if ledState == 0:
            on()
            ledState = 1
            button.wait_for_release()   # wait or otherwise the script will trigger again while the button is still pressed
            continue        # stop the current loop iteration here and start again
        if ledState == 1:   # alternative: if not ledState == 0: or else: 
             off()
             ledState = 0
             button.wait_for_release()

Example 2: toggle state with functions (led is on, only while button is pressed)

from gpiozero import LED, Button

led = LED(25) # GPIO 25
ledState= 0
button = Button(2) # GPIO 2

def on():
    led.on() # Since Python doesn't have function-enclosing parentheses, here are 4 spacebars to assign the contents to the function.

def off():
    led.off()


while True : # otherwise the script will only work once
    button.wait_for_press()
    on()
    button.wait_for_release()
    off()

Example 3 using functions and "when_pressed" && "when_released"

Useful link: https://gpiozero.readthedocs.io/en/stable/faq.html

from gpiozero import LED, Button
from signal import pause

led = LED(25) # GPIO 25
button = Button(2) # GPIO 2

def on():
    led.on() # Since Python doesn't have function-enclosing parentheses, here are 4 spacebars to assign the contents to the function.

def off():
    led.off()

button.when_pressed = on # Contrary to expectations, there should be no parentheses after the function call
button.when_released = off

pause() # prevents the script from stopping after it read through everything. The pause function enables the script to keep on listening for button presses