gpiozero
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!
gpiozero
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 ~gpiozero.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:
examples/led_1.py
Alternatively:
examples/led_2.py
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 keep-your-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:
examples/led_variable_brightness.py
Similarly to blinking on and off continuously, a PWMLED can pulse (fade in and out continuously):
examples/led_pulse.py
Check if a Button
is pressed:
examples/button_1.py
Wait for a button to be pressed before continuing:
examples/button_2.py
Run a function every time the button is pressed:
examples/button_3.py
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:
examples/button_4.py
Turn on an LED
when a Button
is pressed:
examples/button_led_1.py
Alternatively:
examples/button_led_2.py
Using the button press to trigger ~picamera.PiCamera
to take a picture using button.when_pressed = camera.capture
would not work because the ~picamera.PiCamera.capture
method requires an output
parameter. However, this can be achieved using a custom function which requires no parameters:
examples/button_camera_1.py
Another example could use one button to start and stop the camera preview, and another to capture:
examples/button_camera_2.py
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:
examples/button_shutdown.py
A collection of LEDs can be accessed using LEDBoard
:
examples/led_board_1.py
Using LEDBoard
with pwm=True
allows each LED's brightness to be controlled:
examples/led_board_2.py
See more LEDBoard
examples in the advanced LEDBoard recipes
<ledboard-advanced>
.
A collection of LEDs can be treated like a bar graph using LEDBarGraph
:
examples/led_bargraph_2.py
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:
examples/led_bargraph_2.py
A full traffic lights system.
Using a TrafficLights
kit like Pi-Stop:
examples/traffic_lights_1.py
Alternatively:
examples/traffic_lights_2.py
Using LED
components:
examples/traffic_lights_3.py
Capture a picture with the camera module every time a button is pressed:
examples/button_stop_motion.py
See Push Button Stop Motion for a full resource.
When you see the light come on, the first person to press their button wins!
examples/reaction_game.py
See Quick Reaction Game for a full resource.
Each button plays a different sound!
examples/music_box.py
See GPIO Music Box for a full resource.
While the button is pressed down, the buzzer and all the lights come on.
FishDish
:
examples/all_on_1.py
Ryanteck TrafficHat
:
examples/all_on_2.py
Using LED
, Buzzer
, and Button
components:
examples/all_on_3.py
Making colours with an RGBLED
:
examples/rgbled.py
Light an LED
when a MotionSensor
detects motion:
examples/motion_sensor.py
Have a LightSensor
detect light and dark:
examples/light_sensor_1.py
Run a function when the light changes:
examples/light_sensor_2.py
Or make a PWMLED
change brightness according to the detected light level:
examples/light_sensor_3.py
Have a DistanceSensor
detect the distance to the nearest object:
examples/distance_sensor_1.py
Run a function when something gets near the sensor:
examples/distance_sensor_2.py
Spin a Motor
around forwards and backwards:
examples/motor.py
Make a Robot
drive around in (roughly) a square:
examples/robot_1.py
Make a robot with a distance sensor that runs away when things get within 20cm of it:
examples/robot_2.py
Use four GPIO buttons as forward/back/left/right controls for a robot:
examples/robot_buttons_1.py
Use up/down/left/right keys to control a robot:
examples/robot_keyboard_1.py
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:
examples/robot_keyboard_2.py
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:
examples/robot_motion_1.py
Alternatively:
examples/robot_motion_2.py
Continually print the value of a potentiometer (values between 0 and 1) connected to a MCP3008
analog to digital converter:
examples/pot_1.py
Present the value of a potentiometer on an LED bar graph using PWM to represent states that won't "fill" an LED:
examples/pot_2.py
Wire a TMP36 temperature sensor to the first channel of an MCP3008
analog to digital converter:
examples/thermometer.py
Wire up three potentiometers (for red, green and blue) and use each of their values to make up the colour of the LED:
examples/rgbled_pot_1.py
Alternatively, the following example is identical, but uses the ~SourceMixin.source
property rather than a while
loop:
examples/rgbled_pot_2.py
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:
examples/timed_heat_lamp.py
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:
examples/internet_status_indicator.py
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:
examples/cpu_temperature_bar_graph.py
Continue to:
recipes_advanced
recipes_remote_gpio