The following recipes demonstrate some of the capabilities of the GPIO Zero library. Please note that all recipes are written assuming Python 3. Recipes may work under Python 2, but no guarantees!
In Python, libraries and functions used in a script must be imported by name at the top of the file, with the exception of the functions built into Python by default.
For example, to use the Button interface from GPIO Zero, it should be explicitly imported:
from gpiozero import Button
Now Button is available directly in your script:
button = Button(2)
Alternatively, the whole GPIO Zero library can be imported:
import gpiozero
In this case, all references to items within GPIO Zero must be prefixed:
button = gpiozero.Button(2)
This library uses Broadcom (BCM) pin numbering for the GPIO pins, as opposed to physical (BOARD) numbering. Unlike in the RPi.GPIO library, this is not configurable.
Any pin marked “GPIO” in the diagram below can be used as a pin number. For example, if an LED was attached to “GPIO17” you would specify the pin number as 17 rather than 11:
Turn an LED on and off repeatedly:
from gpiozero import LED
from time import sleep
red = LED(17)
while True:
red.on()
sleep(1)
red.off()
sleep(1)
Alternatively:
from gpiozero import LED
from signal import pause
red = LED(17)
red.blink()
pause()
Note
Reaching the end of a Python script will terminate the process and GPIOs may be reset. Keep your script alive with signal.pause(). See How do I keep my script running? for more information.
Any regular LED can have its brightness value set using PWM (pulse-width-modulation). In GPIO Zero, this can be achieved using PWMLED using values between 0 and 1:
from gpiozero import PWMLED
from time import sleep
led = PWMLED(17)
while True:
led.value = 0 # off
sleep(1)
led.value = 0.5 # half brightness
sleep(1)
led.value = 1 # full brightness
sleep(1)
Similarly to blinking on and off continuously, a PWMLED can pulse (fade in and out continuously):
from gpiozero import PWMLED
from signal import pause
led = PWMLED(17)
led.pulse()
pause()
Check if a Button is pressed:
from gpiozero import Button
button = Button(2)
while True:
if button.is_pressed:
print("Button is pressed")
else:
print("Button is not pressed")
Wait for a button to be pressed before continuing:
from gpiozero import Button
button = Button(2)
button.wait_for_press()
print("Button was pressed")
Run a function every time the button is pressed:
from gpiozero import Button
from signal import pause
def say_hello():
print("Hello!")
button = Button(2)
button.when_pressed = say_hello
pause()
Note
Note that the line button.when_pressed = say_hello does not run the function say_hello, rather it creates a reference to the function to be called when the button is pressed. Accidental use of button.when_pressed = say_hello() would set the when_pressed action to None (the return value of this function) which would mean nothing happens when the button is pressed.
Similarly, functions can be attached to button releases:
from gpiozero import Button
from signal import pause
def say_hello():
print("Hello!")
def say_goodbye():
print("Goodbye!")
button = Button(2)
button.when_pressed = say_hello
button.when_released = say_goodbye
pause()
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.values
pause()
Using the button press to trigger PiCamera to take a picture using button.when_pressed = camera.capture would not work because the capture() method requires an output parameter. However, this can be achieved using a custom function which requires no parameters:
from gpiozero import Button
from picamera import PiCamera
from datetime import datetime
from signal import pause
button = Button(2)
camera = PiCamera()
def capture():
datetime = datetime.now().isoformat()
camera.capture('/home/pi/%s.jpg' % datetime)
button.when_pressed = capture
pause()
Another example could use one button to start and stop the camera preview, and another to capture:
from gpiozero import Button
from picamera import PiCamera
from datetime import datetime
from signal import pause
left_button = Button(2)
right_button = Button(3)
camera = PiCamera()
def capture():
datetime = datetime.now().isoformat()
camera.capture('/home/pi/%s.jpg' % datetime)
left_button.when_pressed = camera.start_preview
left_button.when_released = camera.stop_preview
right_button.when_pressed = capture
pause()
The Button class also provides the ability to run a function when the button has been held for a given length of time. This example will shut down the Raspberry Pi when the button is held for 2 seconds:
from gpiozero import Button
from subprocess import check_call
from signal import pause
def shutdown():
check_call(['sudo', 'poweroff'])
shutdown_btn = Button(17, hold_time=2)
shutdown_btn.when_held = shutdown
pause()
A collection of LEDs can be accessed using LEDBoard:
from gpiozero import LEDBoard
from time import sleep
from signal import pause
leds = LEDBoard(5, 6, 13, 19, 26)
leds.on()
sleep(1)
leds.off()
sleep(1)
leds.value = (1, 0, 1, 0, 1)
sleep(1)
leds.blink()
pause()
Using LEDBoard with pwm=True allows each LED’s brightness to be controlled:
from gpiozero import LEDBoard
from signal import pause
leds = LEDBoard(5, 6, 13, 19, 26, pwm=True)
leds.value = (0.2, 0.4, 0.6, 0.8, 1.0)
pause()
See more LEDBoard examples in the advanced LEDBoard recipes.
A collection of LEDs can be treated like a bar graph using LEDBarGraph:
from gpiozero import LEDBarGraph
from time import sleep
graph = LEDBarGraph(5, 6, 13, 19, 26, pwm=True)
graph.value = 1/10 # (0.5, 0, 0, 0, 0)
sleep(1)
graph.value = 3/10 # (1, 0.5, 0, 0, 0)
sleep(1)
graph.value = -3/10 # (0, 0, 0, 0.5, 1)
sleep(1)
graph.value = 9/10 # (1, 1, 1, 1, 0.5)
sleep(1)
graph.value = 95/100 # (1, 1, 1, 1, 0.75)
sleep(1)
Note values are essentially rounded to account for the fact LEDs can only be on or off when pwm=False (the default).
However, using LEDBarGraph with pwm=True allows more precise values using LED brightness:
from gpiozero import LEDBarGraph
from time import sleep
graph = LEDBarGraph(5, 6, 13, 19, 26, pwm=True)
graph.value = 1/10 # (0.5, 0, 0, 0, 0)
sleep(1)
graph.value = 3/10 # (1, 0.5, 0, 0, 0)
sleep(1)
graph.value = -3/10 # (0, 0, 0, 0.5, 1)
sleep(1)
graph.value = 9/10 # (1, 1, 1, 1, 0.5)
sleep(1)
graph.value = 95/100 # (1, 1, 1, 1, 0.75)
sleep(1)
A full traffic lights system.
Using a TrafficLights kit like Pi-Stop:
from gpiozero import TrafficLights
from time import sleep
lights = TrafficLights(2, 3, 4)
lights.green.on()
while True:
sleep(10)
lights.green.off()
lights.amber.on()
sleep(1)
lights.amber.off()
lights.red.on()
sleep(10)
lights.amber.on()
sleep(1)
lights.green.on()
lights.amber.off()
lights.red.off()
Alternatively:
from gpiozero import TrafficLights
from time import sleep
from signal import pause
lights = TrafficLights(2, 3, 4)
def traffic_light_sequence():
while True:
yield (0, 0, 1) # green
sleep(10)
yield (0, 1, 0) # amber
sleep(1)
yield (1, 0, 0) # red
sleep(10)
yield (1, 1, 0) # red+amber
sleep(1)
lights.source = traffic_light_sequence()
pause()
Using LED components:
from gpiozero import LED
from time import sleep
red = LED(2)
amber = LED(3)
green = LED(4)
green.on()
amber.off()
red.off()
while True:
sleep(10)
green.off()
amber.on()
sleep(1)
amber.off()
red.on()
sleep(10)
amber.on()
sleep(1)
green.on()
amber.off()
red.off()
Capture a picture with the camera module every time a button is pressed:
from gpiozero import Button
from picamera import PiCamera
button = Button(2)
camera = PiCamera()
camera.start_preview()
frame = 1
while True:
button.wait_for_press()
camera.capture('/home/pi/frame%03d.jpg' % frame)
frame += 1
See Push Button Stop Motion for a full resource.
When you see the light come on, the first person to press their button wins!
from gpiozero import Button, LED
from time import sleep
import random
led = LED(17)
player_1 = Button(2)
player_2 = Button(3)
time = random.uniform(5, 10)
sleep(time)
led.on()
while True:
if player_1.is_pressed:
print("Player 1 wins!")
break
if player_2.is_pressed:
print("Player 2 wins!")
break
led.off()
See Quick Reaction Game for a full resource.
Each button plays a different sound!
from gpiozero import Button
import pygame.mixer
from pygame.mixer import Sound
from signal import pause
pygame.mixer.init()
button_sounds = {
Button(2): Sound("samples/drum_tom_mid_hard.wav"),
Button(3): Sound("samples/drum_cymbal_open.wav"),
}
for button, sound in button_sounds.items():
button.when_pressed = sound.play
pause()
See GPIO Music Box for a full resource.
While the button is pressed down, the buzzer and all the lights come on.
from gpiozero import FishDish
from signal import pause
fish = FishDish()
fish.button.when_pressed = fish.on
fish.button.when_released = fish.off
pause()
Ryanteck TrafficHat:
from gpiozero import TrafficHat
from signal import pause
th = TrafficHat()
th.button.when_pressed = th.on
th.button.when_released = th.off
pause()
Using LED, Buzzer, and Button components:
from gpiozero import LED, Buzzer, Button
from signal import pause
button = Button(2)
buzzer = Buzzer(3)
red = LED(4)
amber = LED(5)
green = LED(6)
things = [red, amber, green, buzzer]
def things_on():
for thing in things:
thing.on()
def things_off():
for thing in things:
thing.off()
button.when_pressed = things_on
button.when_released = things_off
pause()
Making colours with an RGBLED:
from gpiozero import RGBLED
from time import sleep
led = RGBLED(red=9, green=10, blue=11)
led.red = 1 # full red
sleep(1)
led.red = 0.5 # half red
sleep(1)
led.color = (0, 1, 0) # full green
sleep(1)
led.color = (1, 0, 1) # magenta
sleep(1)
led.color = (1, 1, 0) # yellow
sleep(1)
led.color = (0, 1, 1) # cyan
sleep(1)
led.color = (1, 1, 1) # white
sleep(1)
led.color = (0, 0, 0) # off
sleep(1)
# slowly increase intensity of blue
for n in range(100):
led.blue = n/100
sleep(0.1)
Light an LED when a MotionSensor detects motion:
from gpiozero import MotionSensor, LED
from signal import pause
pir = MotionSensor(4)
led = LED(16)
pir.when_motion = led.on
pir.when_no_motion = led.off
pause()
Have a LightSensor detect light and dark:
from gpiozero import LightSensor
sensor = LightSensor(18)
while True:
sensor.wait_for_light()
print("It's light! :)")
sensor.wait_for_dark()
print("It's dark :(")
Run a function when the light changes:
from gpiozero import LightSensor, LED
from signal import pause
sensor = LightSensor(18)
led = LED(16)
sensor.when_dark = led.on
sensor.when_light = led.off
pause()
Or make a PWMLED change brightness according to the detected light level:
from gpiozero import LightSensor, PWMLED
from signal import pause
sensor = LightSensor(18)
led = PWMLED(16)
led.source = sensor.values
pause()
Have a DistanceSensor detect the distance to the nearest object:
from gpiozero import DistanceSensor
from time import sleep
sensor = DistanceSensor(23, 24)
while True:
print('Distance to nearest object is', sensor.distance, 'm')
sleep(1)
Run a function when something gets near the sensor:
from gpiozero import DistanceSensor, LED
from signal import pause
sensor = DistanceSensor(23, 24, max_distance=1, threshold_distance=0.2)
led = LED(16)
sensor.when_in_range = led.on
sensor.when_out_of_range = led.off
pause()
Spin a Motor around forwards and backwards:
from gpiozero import Motor
from time import sleep
motor = Motor(forward=4, backward=14)
while True:
motor.forward()
sleep(5)
motor.backward()
sleep(5)
Make a Robot drive around in (roughly) a square:
from gpiozero import Robot
from time import sleep
robot = Robot(left=(4, 14), right=(17, 18))
for i in range(4):
robot.forward()
sleep(10)
robot.right()
sleep(1)
Make a robot with a distance sensor that runs away when things get within 20cm of it:
from gpiozero import Robot, DistanceSensor
from signal import pause
sensor = DistanceSensor(23, 24, max_distance=1, threshold_distance=0.2)
robot = Robot(left=(4, 14), right=(17, 18))
sensor.when_in_range = robot.backward
sensor.when_out_of_range = robot.stop
pause()
Use four GPIO buttons as forward/back/left/right controls for a robot:
from gpiozero import Robot, Button
from signal import pause
robot = Robot(left=(4, 14), right=(17, 18))
left = Button(26)
right = Button(16)
fw = Button(21)
bw = Button(20)
fw.when_pressed = robot.forward
fw.when_released = robot.stop
left.when_pressed = robot.left
left.when_released = robot.stop
right.when_pressed = robot.right
right.when_released = robot.stop
bw.when_pressed = robot.backward
bw.when_released = robot.stop
pause()
Use up/down/left/right keys to control a robot:
import curses
from gpiozero import Robot
robot = Robot(left=(4, 14), right=(17, 18))
actions = {
curses.KEY_UP: robot.forward,
curses.KEY_DOWN: robot.backward,
curses.KEY_LEFT: robot.left,
curses.KEY_RIGHT: robot.right,
}
def main(window):
next_key = None
while True:
curses.halfdelay(1)
if next_key is None:
key = window.getch()
else:
key = next_key
next_key = None
if key != -1:
# KEY DOWN
curses.halfdelay(3)
action = actions.get(key)
if action is not None:
action()
next_key = key
while next_key == key:
next_key = window.getch()
# KEY UP
robot.stop()
curses.wrapper(main)
Note
This recipe uses the standard curses module. This module requires that Python is running in a terminal in order to work correctly, hence this recipe will not work in environments like IDLE.
If you prefer a version that works under IDLE, the following recipe should suffice:
from gpiozero import Robot
from evdev import InputDevice, list_devices, ecodes
robot = Robot(left=(4, 14), right=(17, 18))
# Get the list of available input devices
devices = [InputDevice(device) for device in list_devices()]
# Filter out everything that's not a keyboard. Keyboards are defined as any
# device which has keys, and which specifically has keys 1..31 (roughly Esc,
# the numeric keys, the first row of QWERTY plus a few more) and which does
# *not* have key 0 (reserved)
must_have = {i for i in range(1, 32)}
must_not_have = {0}
devices = [
dev
for dev in devices
for keys in (set(dev.capabilities().get(ecodes.EV_KEY, [])),)
if must_have.issubset(keys)
and must_not_have.isdisjoint(keys)
]
# Pick the first keyboard
keyboard = devices[0]
keypress_actions = {
ecodes.KEY_UP: robot.forward,
ecodes.KEY_DOWN: robot.backward,
ecodes.KEY_LEFT: robot.left,
ecodes.KEY_RIGHT: robot.right,
}
for event in keyboard.read_loop():
if event.type == ecodes.EV_KEY and event.code in keypress_actions:
if event.value == 1: # key down
keypress_actions[event.code]()
if event.value == 0: # key up
robot.stop()
Note
This recipe uses the third-party evdev module. Install this library with sudo pip3 install evdev first. Be aware that evdev will only work with local input devices; this recipe will not work over SSH.
Make a robot drive forward when it detects motion:
from gpiozero import Robot, MotionSensor
from signal import pause
robot = Robot(left=(4, 14), right=(17, 18))
pir = MotionSensor(5)
pir.when_motion = robot.forward
pir.when_no_motion = robot.stop
pause()
Alternatively:
from gpiozero import Robot, MotionSensor
from signal import pause
robot = Robot(left=(4, 14), right=(17, 18))
pir = MotionSensor(5)
robot.source = zip(pir.values, pir.values)
pause()
Continually print the value of a potentiometer (values between 0 and 1) connected to a MCP3008 analog to digital converter:
from gpiozero import MCP3008
pot = MCP3008(channel=0)
while True:
print(pot.value)
Present the value of a potentiometer on an LED bar graph using PWM to represent states that won’t “fill” an LED:
from gpiozero import LEDBarGraph, MCP3008
from signal import pause
graph = LEDBarGraph(5, 6, 13, 19, 26, pwm=True)
pot = MCP3008(channel=0)
graph.source = pot.values
pause()
Wire a TMP36 temperature sensor to the first channel of an MCP3008 analog to digital converter:
from gpiozero import MCP3008
from time import sleep
def convert_temp(gen):
for value in gen:
yield (value * 3.3 - 0.5) * 100
adc = MCP3008(channel=0)
for temp in convert_temp(adc.values):
print('The temperature is', temp, 'C')
sleep(1)
Wire up three potentiometers (for red, green and blue) and use each of their values to make up the colour of the LED:
from gpiozero import RGBLED, MCP3008
led = RGBLED(red=2, green=3, blue=4)
red_pot = MCP3008(channel=0)
green_pot = MCP3008(channel=1)
blue_pot = MCP3008(channel=2)
while True:
led.red = red_pot.value
led.green = green_pot.value
led.blue = blue_pot.value
Alternatively, the following example is identical, but uses the source property rather than a while loop:
from gpiozero import RGBLED, MCP3008
from signal import pause
led = RGBLED(2, 3, 4)
red_pot = MCP3008(0)
green_pot = MCP3008(1)
blue_pot = MCP3008(2)
led.source = zip(red_pot.values, green_pot.values, blue_pot.values)
pause()
Note
Please note the example above requires Python 3. In Python 2, zip() doesn’t support lazy evaluation so the script will simply hang.
If you have a pet (e.g. a tortoise) which requires a heat lamp to be switched on for a certain amount of time each day, you can use an Energenie Pi-mote to remotely control the lamp, and the TimeOfDay class to control the timing:
from gpiozero import Energenie, TimeOfDay
from datetime import time
from signal import pause
lamp = Energenie(1)
daytime = TimeOfDay(time(8), time(20))
lamp.source = daytime.values
lamp.source_delay = 60
pause()
You can use a pair of green and red LEDs to indicate whether or not your internet connection is working. Simply use the PingServer class to identify whether a ping to google.com is successful. If successful, the green LED is lit, and if not, the red LED is lit:
from gpiozero import LED, PingServer
from gpiozero.tools import negated
from signal import pause
green = LED(17)
red = LED(18)
google = PingServer('google.com')
green.source = google.values
green.source_delay = 60
red.source = negated(green.values)
pause()
You can read the Raspberry Pi’s own CPU temperature using the built-in CPUTemperature class, and display this on a “bar graph” of LEDs:
from gpiozero import LEDBarGraph, CPUTemperature
from signal import pause
cpu = CPUTemperature(min_temp=50, max_temp=90)
leds = LEDBarGraph(2, 3, 4, 5, 6, 7, 8, pwm=True)
leds.source = cpu.values
pause()