KevinMidboe/python-gpiozero
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7429c031175fb1ae989af202bcda5cf12a141954
python-gpiozero/docs/notes.md
Dave Jones 7429c03117 Docs clean up part 1 
Big push on getting the docs cleaned up before 1.0. Proper wrapping of
everything so it's decently viewable from the command line (or as
decently viewable as markdown can be - the tables will never look great
from the command line).

Only one code change in this PR: rename bouncetime to bounce_time
(everything else is PEP-8, so this probably should be too) and change
its units to seconds from milliseconds (again, all other durations in
the library are in seconds, so it feels inconsistent that this one
isn't; for the sake of those who won't read the docs - which is most
people - I figure consistency helps with guessing!).
2015-10-03 16:24:12 +01:00

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Notes

  1. 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)

  2. Wiring

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

  3. 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()