python-gpiozero/docs/notes.md

Notes

BCM pin numbering

This library uses Broadcom (BCM) pin numbering for the GPIO pins, as opposed to BOARD. Unlike the RPi.GPIO library, this is not configurable.

Any pin marked GPIO can be used for generic components.

The BCM pin layout is as follows:

3V3	5V
GPIO2	5V
GPIO3	GND
GPIO4	GPIO14
GND	GPIO15
GPIO17	GPIO18
GPIO27	GND
GPIO22	GPIO23
3V3	GPIO24
GPIO10	GND
GPIO9	GPIO25
GPIO11	GPIO8
GND	GPIO7
DNC	DNC
GPIO5	GND
GPIO6	GPIO12
GPIO13	GND
GPIO19	GPIO16
GPIO26	GPIO20
GND	GPIO21

• GND = Ground
• 3V3 = 3.3 Volts
• 5V = 5 Volts
• DNC = Do not connect (special use pins)

Wiring

All components must be wired up correctly before using with this library.

Keep your program alive with signal.pause

The following program looks like it should turn an LED on:

from gpiozero import led

led = LED(2)
led.on()

And it does, if you're using the Python shell, IPython shell or IDLE shell, but if you saved this program as a Python file and ran it, it would flash on for a moment then the program would end and it would turn off.

The following file includes an intentional pause to keep the program alive:

from gpiozero import LED
from signal import pause

led = LED(2)
led.on()
pause()

Now running the program will stay running, leaving the LED on, until it is forced to quit.

Similarly, when setting up callbacks on button presses or other input devices, the program needs to be running for the events to be detected:

from gpiozero import Button
from signal import pause

button = Button(2)
button.when_pressed = lambda: print("Button was pressed!")
pause()