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84 lines
2.2 KiB
Markdown
84 lines
2.2 KiB
Markdown
# Notes
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1. **BCM pin numbering**
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This library uses BCM pin numbering for the GPIO pins, as opposed to BOARD. Unlike the `RPi.GPIO` library, it is not configurable.
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Any pin marked `GPIO` can be used for generic components.
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The BCM pin layout is as follows:
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|-----------:|:-----------|
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| 3V3 | 5V |
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| **GPIO2** | 5V |
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| **GPIO3** | GND |
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| **GPIO4** | **GPIO14** |
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| GND | **GPIO15** |
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| **GPIO17** | **GPIO18** |
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| **GPIO27** | GND |
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| **GPIO22** | **GPIO23** |
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| 3V3 | **GPIO24** |
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| **GPIO10** | GND |
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| **GPIO9** | **GPIO25** |
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| **GPIO11** | **GPIO8** |
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| GND | **GPIO7** |
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| DNC | DNC |
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| **GPIO5** | GND |
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| **GPIO6** | **GPIO12** |
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| **GPIO13** | GND |
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| **GPIO19** | **GPIO16** |
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| **GPIO26** | **GPIO20** |
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| GND | **GPIO21** |
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- *GND = Ground*
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- *3V3 = 3.3 Volts*
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- *5V = 5 Volts*
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- *DNC = Do not connect (special use pins)*
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1. **Wiring**
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All components must be wired up correctly before using with this library.
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1. **Keep your program alive with `signal.pause`**
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The following program looks like it should turn an LED on:
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```python
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from gpiozero import led
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led = LED(2)
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led.on()
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```
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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.
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The following file includes an intentional `pause` to keep the program alive:
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```python
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from gpiozero import LED
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from signal import pause
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led = LED(2)
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led.on()
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pause()
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```
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Now running the program will stay running, leaving the LED on, until it is forced to quit.
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Similarly, when setting up callbacks on button presses or other input devices, the program needs to be running for the events to be detected:
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```python
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from gpiozero import Button
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from signal import pause
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button = Button(2)
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button.when_pressed = lambda: print("Button was pressed!")
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pause()
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```
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