Programming paradigms for physical computing and IoT

Talk given at London Raspberry Pint April 2018 meetup

Transcript

1. Programming paradigms for
   physical computing and IoT
   Ben Nuttall
   Raspberry Pi Foundation
   UK Charity 1129409
   

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2. Ben Nuttall
   ●
   Raspberry Pi Community Manager
   ●
   Based in Cambridge
   ●
   Creator of gpiozero python library and
   piwheels project
   ●
   Columnist on opensource.com
   ●
   github.com/bennuttall
   ●
   twitter.com/ben_nuttall
   ●
   ben@raspberrypi.org
   

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3. GPIO Pins – General Purpose
   Input/Output
   

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4. GPIO Zero: a friendly API for GPIO devices
   from gpiozero import LED
   led = LED(17)
   led.on()
   

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5. Multi-paradigm: procedural (polling)
   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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6. Multi-paradigm: procedural (blocking)
   from gpiozero import LED, Button
   led = LED(17)
   button = Button(4)
   while True:
   button.wait_for_press()
   led.on()
   button.wait_for_release()
   led.off()
   

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

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9. GPIO Zero supports...
   

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10. GPIO Zero Device Hierarchy!
    

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11. .value
    >>> led = PWMLED(17)
    >>> led.value
    0.0
    >>> led.on()
    >>> led.value
    1.0
    >>> led.value = 0
    

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12. .value
    >>> led = PWMLED(17)
    >>> pot = MCP3008()
    >>> led.value
    0.0
    >>> pot.value
    0.510145879738202
    >>> led.value = pot.value
    

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13. .value
    >>> while True:
    ... led.value = pot.value
    

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

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

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16. Source / Values
    from gpiozero import LED, Button
    led = LED(17)
    button = Button(2)
    led.source = button.values
    

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17. Processing values
    Output Device
    .value
    .values
    .source
    Input Device
    .value
    .values
    function
    

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18. Source tools
    from gpiozero import Button, LED
    from gpiozero.tools import negated
    led = LED(4)
    btn = Button(17)
    led.source = negated(btn.values)
    

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19. Combining values
    Output Device
    .value
    .values
    .source
    Input Device
    .value
    .values
    Source tool
    Input Device
    .value
    .values
    

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20. Source tools
    from gpiozero import Button, LED
    from gpiozero.tools import all_values
    button_a = Button(2)
    button_b = Button(3)
    led = LED(17)
    led.source = all_values(button_a.values, button_b.values)
    

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21. Cross-platform
    ●
    Raspbian (Raspberry Pi)
    ●
    Raspberry Pi Desktop x86 (PC)
    ●
    Linux (PC)
    ●
    Windows (PC)
    ●
    Mac OS (Mac)
    

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22. Supporting multiple back-ends
    ●
    RPi.GPIO
    ●
    Implemented in C, current default
    ●
    RPIO
    ●
    Implemented in C
    ●
    pigpio
    ●
    Python wrapper for C library, runs as daemon, remote pins
    ●
    Native
    ●
    Pure Python, limited functionality, experimental
    ●
    MockPin & MockPWMPin
    ●
    Pure Python, used in test suite
    

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23. MockPin
    $ GPIOZERO_PIN_FACTORY=mock python3
    >>> from gpiozero import LED
    >>> led = LED(22)
    >>> led.blink()
    >>> led.value
    True
    >>> led.value
    False
    

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24. MockPin
    >>> from gpiozero import LED, Button
    >>> led = LED(22)
    >>> button = Button(23)
    >>> led.source = button.values
    >>> led.value
    False
    >>> button.pin.drive_low()
    >>> led.value
    True
    

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25. pigpio - remote GPIO from Pi or PC
    

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26. pigpio - remote GPIO from Pi or PC
    from gpiozero import LED
    from gpiozero.pins.pigpio import PiGPIOFactory
    factory = PiGPIOFactory('192.168.0.2')
    led = LED(22, pin_factory=factory)
    led.blink()
    

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27. 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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28. Raspberry Pi Desktop x86
    

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29. Raspberry Pi Desktop x86 – Remote GPIO
    

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30. Raspberry Pi Desktop x86 – GPIO
    expander
    

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31. Internal devices
    ●
    TimeOfDay
    ●
    PingServer
    ●
    CPUTemperature
    ●
    More coming soon
    ●
    Make your own!
    

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32. Energenie tortoise lamp
    from gpiozero import Energenie, TimeOfDay
    from datetime import time
    lamp = Energenie(1)
    daytime = TimeOfDay(time(9), time(18))
    lamp.source = daytime.values
    

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33. Is the internet working?
    from gpiozero import LED, PingServer
    from gpiozero.tools import negated
    green = LED(17)
    red = LED(18)
    google = PingServer('google.com')
    green.source = google.values
    green.source_delay = 60
    red.source = negated(green.values)
    

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34. CPU Temperature
    from gpiozero import LEDBarGraph, CPUTemperature
    cpu = CPUTemperature(min_temp=50, max_temp=90)
    leds = LEDBarGraph(2, 3, 4, 5, 6, 7, 8, pwm=True)
    leds.source = cpu.values
    

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35. Custom internal devices
    from gpiozero import InternalDevice
    class FileReader(InternalDevice):
    @property
    def value(self):
    with open('value.txt') as f:
    return int(f.read().strip())
    

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36. Blue Dot
    

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37. Multi-paradigm: procedural (polling)
    from gpiozero import LED
    from bluedot import BlueDot
    led = LED(17)
    bd = BlueDot()
    while True:
    if bd.is_pressed:
    led.on()
    else:
    led.off()
    

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38. Multi-paradigm: procedural (blocking)
    from gpiozero import LED
    from bluedot import BlueDot
    led = LED(17)
    bd = BlueDot()
    while True:
    bd.wait_for_press()
    led.on()
    bd.wait_for_release()
    led.off()
    

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39. Multi-paradigm: event-driven
    from gpiozero import LED
    from bluedot import BlueDot
    led = LED(17)
    bd = BlueDot()
    bd.when_pressed = led.on
    bd.when_released = led.off
    

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40. Multi-paradigm: declarative
    from gpiozero import LED
    from bluedot import BlueDot
    led = LED(17)
    bd = BlueDot()
    led.source = bd.values
    

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41. IoT devices?
    from somelib import GardenLight, LightSensor, MotionSensor
    from gpiozero.tools import all_values, negated
    garden = GardenLight()
    light = LightSensor()
    motion = MotionSensor()
    garden.source = all_values(negated(light.values), motion.values)
    

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42. guizero
    

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43. GitHub
    

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44. pinout command line tool
    

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45. Read the docs!
    

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46. The MagPi
    

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47. Programming paradigms for
    physical computing and IoT
    Ben Nuttall
    Raspberry Pi Foundation
    UK Charity 1129409
    

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