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2b50b9bd8c
Co-authored-by: sfalexrog <sfalexrog@gmail.com> * Rework the structure. * Add Clever 4 assembling instruction. * Rework setup articles. * Many additional changes.
101 lines
3.0 KiB
Markdown
101 lines
3.0 KiB
Markdown
# Working with GPIO
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A GPIO (General-Purpose Input/Output) pin is a programmable digital signal pin on a circuit board or a microcontroller that may act as an input or an output. Raspberry Pi has a set of easily accessible GPIO pins, some of which have hardware <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 [`pigpio`](http://abyz.me.uk/rpi/pigpio) library for interfacing with the GPIO pins is already preinstalled on [the RPi image](image.md). 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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To enable automatic launch of the daemon, run:
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```bash
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sudo systemctl enable pigpiod.service
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```
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> **Warning** `pigpiod` may interfere with [LED strip](leds.md) if configured improperly. Make sure that the strip is connected to GPIO21. On [image versions](image.md) lower than 0.17 change the service start string in `/lib/systemd/system/pigpiod.service` to `ExecStart=/usr/bin/pigpiod -l -t 0 -x 0x0FFF3FF0`.
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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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# set pin 11 mode for output
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pi.set_mode(11, pigpio.OUTPUT)
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# set signal of pin 11 to high
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pi.write(11, 1)
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time.sleep(2)
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# set signal on pin 11 to low
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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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To find out the pins' numbers, consult the [Raspberry Pi pinout](https://pinout.xyz).
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## Connecting servos
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Servo motors are typically 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. To control 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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# set mode of pin 13 to output
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pi.set_mode(13, pigpio.OUTPUT)
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# set 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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# set 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 an electromagnet
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To connect an electromagnet use a field-effect transistor (MOSFET). Connect the MOSFET to one of GPIO-pins of the Raspberry Pi. To control 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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# set mode of pin 15 for output
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pi.set_mode(15, pigpio.OUTPUT)
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# enable the magnet
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pi.write(15, 1)
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time.sleep(2)
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# disable the magnet
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pi.write(15, 0)
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```
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> **Note** A more [comprehensive description](https://elinux.org/RPi_Low-level_peripherals) of the Raspberry Pi GPIO pins and [additional examples](https://elinux.org/RPi_GPIO_Interface_Circuits) of circuits are available at the [Embedded Linux wiki](https://elinux.org/RPi_Hub).
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