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97 lines
2.4 KiB
Markdown
97 lines
2.4 KiB
Markdown
# Working with GPIO
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GPIO (General-Purpose Input/Output) – is a type of Raspberry Pi's pins, with programmatically adjustable and measurable voltage. On some of the pins there also is hardware implemented <abbr title="Pulse-width modulation">PWM</abbr>.
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> **Info** Use the [pinout](https://pinout.xyz) for figuring out, which Raspberry Pi's pins support GPIO and PWM.
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[The RPi image](microsd_images.md) includes [`pigpio`](http://abyz.me.uk/rpi/pigpio/) library for work with GPIO. To interact with this library, run the appropriate daemon:
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```bash
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sudo systemctl start pigpiod.service
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```
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For enabling automatic launch of the daemon, use command:
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```bash
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sudo systemctl enable pigpiod.service
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```
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Example of working with the library:
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```python
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import time
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import pigpio
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# initializing connection to pigpiod
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pi = pigpio.pi()
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# setting pin 11 mode for output
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pi.set_mode(11, pigpio.OUTPUT)
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# enabling signal of pin 11
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pi.write(11, 1)
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time.sleep(2)
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# disabling signal on pin 11
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pi.write(11, 0)
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# ...
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# setting pin 12 mode for input
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pi.set_mode(12, pigpio.INPUT)
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# read the state of pin 12
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level = pi.read(12)
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```
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For finding out pins' numbers, use the [Raspberry Pi pinout](https://pinout.xyz).
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## Connecting servos
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Most of servos are controlled with PWM signal. Extreme positions of servos are reached with signal widths approximately equal to 1000 and 2000 µs. Values for a specific servo can be determined experimentally.
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Connect the signal wire of the servo to one of GPIO-pins of the Raspberry. For controlling a servo, connected to the pin 13, use a code like this:
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```python
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import time
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import pigpio
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pi = pigpio.pi()
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# setting mode of pin 13 to output
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pi.set_mode(13, pigpio.OUTPUT)
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# setting pin 13 to output PWM signal 1000 us
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pi.set_servo_pulsewidth(13, 1000)
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time.sleep(2)
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# setting pin 13 to output PWM signal 2000 us
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pi.set_servo_pulsewidth(13, 2000)
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```
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## Connecting electromagnet
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For connecting an electromagnet, use a field-effect transistor (MOSFET). Connect the MOSFET to one of GPIO-pins of the Raspberry Pi. For controlling the magnet, connected to the pin 15, use a code like this:
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```python
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import time
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import pigpio
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pi = pigpio.pi()
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# setting mode of pin 15 for output
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pi.set_mode(15, pigpio.OUTPUT)
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# enabling the magnet
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pi.write(15, 1)
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time.sleep(2)
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# disabling the magnet
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pi.write(15, 0)
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```
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