Physical Computing with Python and Raspberry Pi - campug

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

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

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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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Raspbian Jessie with PIXEL

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GPIO Pins – General Purpose Input/Output

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

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

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GPIO components

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Add-on boards / HATs

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

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

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GPIO Zero supports...

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GPIO Zero Device Hierarchy!

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

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

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

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

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

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

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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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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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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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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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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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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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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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Picamera image effects

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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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Sense HAT

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

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Astro Pi

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