Physical Computing with Python and Raspberry Pi - campug

Physical Computing with Python and Raspberry Pi - session delivered at the Cambridge Python user group (campug) in January 2017

Transcript

1. Physical Computing with Python
   and Raspberry Pi
   Ben Nuttall
   Raspberry Pi Foundation
   UK Charity 1129409
   

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2. Ben Nuttall
   ●
   Raspberry Pi Community Manager
   ●
   Creator of gpiozero python library
   ●
   github.com/bennuttall
   ●
   @ben_nuttall on Twitter
   

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3. Current models
   ●
   Raspberry Pi 3
   ●
   64-bit quad-core ARMv8
   @ 1.2GHz
   ●
   1GB RAM
   ●
   $35
   ●
   Raspberry Pi Zero
   ●
   32-bit single-core ARMv6
   @ 1GHz
   ●
   512MB RAM
   ●
   $5
   

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4. Raspbian Jessie with PIXEL
   

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5. GPIO Pins – General Purpose Input/Output
   

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6. Physical computing
   ●
   Flashy lights
   ●
   Motors & robots
   ●
   Photo & video
   ●
   Sensors
   ●
   Internet of Things
   ●
   Engaging and empowering
   

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7. GPIO
   ●
   3V3, 5V
   ●
   GPIO, SPI, I2C, UART
   ●
   GPIO = variable 3V3
   

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8. GPIO components
   

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9. Add-on boards / HATs
   

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10. Python - RPi.GPIO
    import RPi.GPIO as GPIO
    from time import sleep
    GPIO.setmode(GPIO.BCM)
    GPIO.setwarnings(False)
    GPIO.setup(17, GPIO.OUT)
    while True:
    GPIO.output(17, GPIO.HIGH)
    sleep(1)
    GPIO.output(17, GPIO.LOW)
    sleep(1)
    

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11. Python - GPIO Zero
    from gpiozero import LED
    from time import sleep
    led = LED(17)
    while True:
    led.on()
    sleep(1)
    led.off()
    sleep(1)
    

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12. Python - GPIO Zero
    from gpiozero import LED
    led = LED(17)
    led.blink()
    

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13. Multi-paradigm: procedural
    from gpiozero import LED, Button
    led = LED(17)
    button = Button(4)
    while True:
    if button.is_pressed:
    led.on()
    else:
    led.off()
    

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14. Multi-paradigm: event-driven
    from gpiozero import LED, Button
    led = LED(17)
    button = Button(4)
    button.when_pressed = led.on
    button.when_released = led.off
    

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15. Multi-paradigm: declarative
    from gpiozero import LED, Button
    led = LED(17)
    button = Button(4)
    led.source = button.values
    

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16. GPIO Zero supports...
    

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17. GPIO Zero Device Hierarchy!
    

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18. Dial up the brightness!
    from gpiozero import PWMLED, MCP3008
    led = PWMLED(2)
    pot = MCP3008()
    while True:
    led.value = pot.value
    

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19. Source / Values
    Output Device
    .value
    .values
    .source
    Input Device
    .value
    .values
    

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20. Source / Values
    Output Device
    .value
    .values
    .source
    Input Device
    .value
    .values
    

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21. Dial up the brightness!
    from gpiozero import PWMLED, MCP3008
    led = PWMLED(2)
    pot = MCP3008()
    led.source = pot.values
    

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22. Source / Values
    Output Device
    .value
    .values
    .source
    Custom generator
    

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23. Source / Values
    Output Device
    .value
    .values
    .source
    Iterator
    

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24. Custom value generators
    Output Device
    .value
    .values
    .source
    Input Device
    .value
    .values
    Custom generator
    

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25. Source Tools
    Output Device
    .value
    .values
    .source
    Input Device
    .value
    .values
    Source tool
    

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26. Source Tools
    from gpiozero import LED, Button
    from gpiozero.tools import all_values
    led = PWMLED(4)
    btn_a = Button(2)
    btn_b = Button(3)
    led.source = all_values(btn_a.values, btn_b.values)
    

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27. Supporting multiple back-ends
    1) RPi.GPIO
    2) RPIO
    3) pigpio
    4) Native
    

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28. pigpio - remote GPIO from Pi or PC
    from gpiozero import LED
    from gpiozero.pins.pigpiod import PiGPIOPin
    led = LED(PiGPIOPin(22, host='192.168.0.2'))
    led.blink()
    

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29. pigpio - remote GPIO from Pi or PC
    $ PIGPIO_ADDR=192.168.0.2 python3 led.py
    from gpiozero import LED
    led = LED(22)
    led.blink()
    

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30. Picamera
    ●
    8 megapixels (v2)
    – v1 was 5mpx
    ●
    Visible light & infra-red
    versions available
    ●
    1080p30, 720p60 and
    VGA90 video
    ●
    Command line interface
    and Python library
    

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31. Picamera - capture
    from picamera import PiCamera
    from time import sleep
    camera = PiCamera()
    camera.start_preview()
    sleep(3)
    camera.capture('/home/pi/Desktop/image.jpg')
    camera.stop_preview()
    

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32. Picamera – record video
    from picamera import PiCamera
    from time import sleep
    camera = PiCamera()
    camera.start_preview()
    camera.start_recording('/home/pi/video.h264')
    sleep(10)
    camera.stop_recording()
    camera.stop_preview()
    

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33. Picamera + GPIO push button
    from picamera import PiCamera
    from gpiozero import Button
    camera = PiCamera()
    button = Button(17)
    camera.start_preview()
    button.wait_for_press()
    camera.capture('/home/pi/Desktop/image.jpg')
    camera.stop_preview()
    

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34. Picamera image effects
    from picamera import PiCamera
    from time import sleep
    camera = PiCamera()
    camera.start_preview()
    for effect in camera.IMAGE_EFFECTS:
    camera.image_effect = effect
    camera.annotate_text = "Effect: %s" % effect
    sleep(5)
    camera.stop_preview()
    

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35. Picamera image effects
    

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36. Sense HAT workshop
    ●
    Special made for Tim Peake's
    Astro Pi mission
    ●
    Sensors, LED display &
    joystick
    ●
    Great for science, games and
    creativity
    ●
    Works on any Pi model
    ●
    Emulators also available
    

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37. Sense HAT
    

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38. Sense HAT
    >>> from sense_hat import SenseHat
    >>> sense = SenseHat()
    >>> sense.show_message(“Hello world”)
    >>> sense.temperature
    >>> sense.humidity
    >>> sense.accelerometer
    >>> sense.gyroscope
    >>> sense.orientation
    

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39. Random sparkles!
    from sense_hat import SenseHat
    from random import randint
    from time import sleep
    sense = SenseHat()
    while True:
    x = randint(0, 7)
    y = randint(0, 7)
    r = randint(0, 255)
    g = randint(0, 255)
    b = randint(0, 255)
    sense.set_pixel(x, y, r, g, b)
    sleep(0.01)
    

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40. ...and breathe...
    while True:
    print(sense.humidity)
    if sense.humidity < 60:
    sense.clear((255, 255, 255))
    sleep(0.5)
    else:
    sense.clear((255, 0, 0))
    sleep(2)
    

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41. Joystick
    def foo(ev):
    if ev.action == 'pressed':
    sense.show_message(str(sense.temperature))
    sense.stick.direction_up = foo
    

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42. Astro Pi
    

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43. Documentation
    ●
    gpiozero.readthedocs.io
    ●
    picamera.readthedocs.io
    ●
    pythonhosted.org/sense-hat
    

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