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
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
3. GPIO Pins – General Purpose Input/Output
4. GPIO Zero: a friendly API for GPIO devices from gpiozero import LED led = LED(17) led.on()
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()
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()
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
8. Multi-paradigm: declarative from gpiozero import LED, Button led = LED(17) button = Button(4) led.source = button.values
9. GPIO Zero supports...
10. GPIO Zero Device Hierarchy!
11. .value >>> led = PWMLED(17) >>> led.value 0.0 >>> led.on() >>> led.value 1.0 >>> led.value = 0
12. .value >>> led = PWMLED(17) >>> pot = MCP3008() >>> led.value 0.0 >>> pot.value 0.510145879738202 >>> led.value = pot.value
13. .value >>> while True: ... led.value = pot.value
14. Source / Values Output Device .value .values .source Input Device .value .values
15. Source / Values Output Device .value .values .source Input Device .value .values
16. Source / Values from gpiozero import LED, Button led = LED(17) button = Button(2) led.source = button.values
17. Processing values Output Device .value .values .source Input Device .value .values function
18. Source tools from gpiozero import Button, LED from gpiozero.tools import negated led = LED(4) btn = Button(17) led.source = negated(btn.values)
19. Combining values Output Device .value .values .source Input Device .value .values Source tool Input Device .value .values
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)
21. Cross-platform • Raspbian (Raspberry Pi) • Raspberry Pi Desktop x86 (PC) • Linux (PC) • Windows (PC) • Mac OS (Mac)
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
23. MockPin $ GPIOZERO_PIN_FACTORY=mock python3 >>> from gpiozero import LED >>> led = LED(22) >>> led.blink() >>> led.value True >>> led.value False
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
25. pigpio - remote GPIO from Pi or PC
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()
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()
28. Raspberry Pi Desktop x86
29. Raspberry Pi Desktop x86 – Remote GPIO
30. Raspberry Pi Desktop x86 – GPIO expander
31. Internal devices • TimeOfDay • PingServer • CPUTemperature • More coming soon • Make your own!
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
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)
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
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())
36. Blue Dot
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()
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()
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
40. Multi-paradigm: declarative from gpiozero import LED from bluedot import BlueDot led = LED(17) bd = BlueDot() led.source = bd.values
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)
42. guizero
43. GitHub
44. pinout command line tool
45. Read the docs!
46. The MagPi
47. Programming paradigms for physical computing and IoT Ben Nuttall Raspberry Pi Foundation UK Charity 1129409