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Programming paradigms for physical computing an...
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Ben Nuttall
April 24, 2018
Programming
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Programming paradigms for physical computing and IoT
Talk given at London Raspberry Pint April 2018 meetup
Ben Nuttall
April 24, 2018
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Transcript
Programming paradigms for physical computing and IoT Ben Nuttall Raspberry
Pi Foundation UK Charity 1129409
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 •
[email protected]
GPIO Pins – General Purpose Input/Output
GPIO Zero: a friendly API for GPIO devices from gpiozero
import LED led = LED(17) led.on()
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()
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()
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
Multi-paradigm: declarative from gpiozero import LED, Button led = LED(17)
button = Button(4) led.source = button.values
GPIO Zero supports...
GPIO Zero Device Hierarchy!
.value >>> led = PWMLED(17) >>> led.value 0.0 >>> led.on()
>>> led.value 1.0 >>> led.value = 0
.value >>> led = PWMLED(17) >>> pot = MCP3008() >>>
led.value 0.0 >>> pot.value 0.510145879738202 >>> led.value = pot.value
.value >>> while True: ... led.value = pot.value
Source / Values Output Device .value .values .source Input Device
.value .values
Source / Values Output Device .value .values .source Input Device
.value .values
Source / Values from gpiozero import LED, Button led =
LED(17) button = Button(2) led.source = button.values
Processing values Output Device .value .values .source Input Device .value
.values function
Source tools from gpiozero import Button, LED from gpiozero.tools import
negated led = LED(4) btn = Button(17) led.source = negated(btn.values)
Combining values Output Device .value .values .source Input Device .value
.values Source tool Input Device .value .values
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)
Cross-platform • Raspbian (Raspberry Pi) • Raspberry Pi Desktop x86
(PC) • Linux (PC) • Windows (PC) • Mac OS (Mac)
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
MockPin $ GPIOZERO_PIN_FACTORY=mock python3 >>> from gpiozero import LED >>>
led = LED(22) >>> led.blink() >>> led.value True >>> led.value False
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
pigpio - remote GPIO from Pi or PC
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()
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()
Raspberry Pi Desktop x86
Raspberry Pi Desktop x86 – Remote GPIO
Raspberry Pi Desktop x86 – GPIO expander
Internal devices • TimeOfDay • PingServer • CPUTemperature • More
coming soon • Make your own!
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
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)
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
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())
Blue Dot
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()
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()
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
Multi-paradigm: declarative from gpiozero import LED from bluedot import BlueDot
led = LED(17) bd = BlueDot() led.source = bd.values
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)
guizero
GitHub
pinout command line tool
Read the docs!
The MagPi
Programming paradigms for physical computing and IoT Ben Nuttall Raspberry
Pi Foundation UK Charity 1129409