Programming paradigms for physical computing and IoT

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

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GPIO Pins – General Purpose Input/Output

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GPIO Zero – a friendly API for GPIO devices from gpiozero import LED led = LED(2) led.blink()

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GPIO Zero – a friendly API for GPIO devices ● Zero-boilerplate Pythonic library ● Intended for use in education ● Simple, guessable API with commonly used names and sensible default values ● Simple introduction, smooth learning curve ● Multi-paradigm ● Extendable

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GPIO Zero supports...

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GPIO Zero device hierarchy ValuesMixin SourceMixin SharedMixin EventsMixin HoldMixin Device GPIODevice SmoothedInputDevice InputDevice AnalogInputDevice SPIDevice MCP3xxx MCP33xx CompositeDevice CompositeOutputDevice LEDCollection InternalDevice DigitalInputDevice Button MotionSensor LightSensor LineSensor DistanceSensor OutputDevice DigitalOutputDevice LED Buzzer PWMOutputDevice PWMLED RGBLED MCP3004 MCP3008 MCP3204 MCP3208 MCP3301 MCP3302 MCP3304 LEDBoard LEDBarGraph PiLiter PiLiterBarGraph TrafficLights PiTraffic TrafficLightsBuzzer FishDish TrafficHat Robot Energenie RyanteckRobot CamJamKitRobot Motor TimeOfDay PingServer

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

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

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

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

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

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

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

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

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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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Source tools – single source conversions ● absoluted ● booleanized ● clamped ● inverted ● negated ● post_delayed ● post_periodic_fltered ● pre_delayed ● pre_periodic_fltered ● quantized ● queued ● smoothed ● scaled

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

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Source tools – combining sources ● all_values ● any_values ● averaged ● multiplied ● summed

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Artifcial values Output Device .value .values .source function

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Source tools – artifcial sources ● alternating_values ● cos_values ● ramping_values ● random_values ● sin_values

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Internal Devices ● TimeOfDay ● CPUTemperature ● PingServer ● More coming soon ● Make your own!

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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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CPU Temperature bar graph 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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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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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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Blue Dot

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

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GPIO Zero: cross-platform – distributed via apt/pip ● Raspberry Pi ● Raspbian, Debian, Ubuntu, etc ● PC & Mac ● Raspberry Pi Desktop x86 ● Linux ● Mac OS ● Windows

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Supporting multiple back-ends ● RPi.GPIO ● Low-level GPIO library, implemented in C (current default) ● RPIO ● Low-level GPIO library, implemented in C (only supports Pi 1) ● pigpio ● Low-level GPIO library, implemented in C ● Runs as a daemon on the Pi, can accept remote commands ● Native ● Pure Python, limited functionality, experimental (included in gpiozero) ● Mock ● Pure Python, used in test suite, useful for testing (included in gpiozero)

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

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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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pigpio - remote GPIO from Pi or PC from gpiozero import LED, Button from gpiozero.pins.pigpio import PiGPIOFactory remote = PiGPIOFactory('192.168.0.2') led = LED(22) btn = Button(22, pin_factory=remote) led.source = btn.values

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Raspberry Pi Desktop x86 OS

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Pi Zero GPIO Expander

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Pi Zero GPIO Expander from gpiozero import LED from gpiozero.pins.pigpio import PiGPIOFactory pizero = PiGPIOFactory('fe80::1%usb0') led = LED(22, pin_factory=pizero) led.blink()

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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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Z-Wave devices & asyncio

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GPIO Zero on GitHub & ReadTheDocs

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piwheels ● Python package repository providing Arm platform wheels for Raspberry Pi ● Builds automated from PyPI releases, plus manual builds e.g. opencv & tensorfoo ● Raspbian is pre-confgured to use piwheels.org as an additional index to PyPI ● Massively reduces pip install time for Raspberry Pi users ● Natively compiled on Raspberry Pi 3 hardoare (Mythic Beasts Pi cloud) ● Repo hosted on single Raspberry Pi serving 300-400k packages per month

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Raspberry Jam ● Independently organised community events around the world ● Family-friendly ● Mix of meetup / conference / workshop styles ● Makers, hackers, programmers & beginners come together ● Find one near you – or start your own! ● raspberrypi.org/jam

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CoderDojo ● Free coding clubs for young people ● Find one near you and volunteer as a mentor – or start a new Dojo in your area ● coderdojo.com

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Raspberry Pi & Python poster session today!

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