GPIO Zero: Developing a friendly Python API for physical computing - campug

Talk on developing GPIO Zero at campug (Cambridge Python User Group)

Transcript

1. GPIO Zero:
   Developing a friendly Python API
   for physical computing
   Ben Nuttall
   Raspberry Pi Foundation
   UK Charity 1129409
   

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2. Ben Nuttall
   ●
   Education Developer Advocate at the
   Raspberry Pi Foundation
   – Runs www.raspberrypi.org
   – Software & project development
   – Learning resources & teacher
   training
   – Outreach
   ●
   Hobbyist turned employee
   ●
   @ben_nuttall on Twitter
   

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3. 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, True)
   sleep(1)
   GPIO.output(17, False)
   sleep(1)
   

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4. Current state of affairs with RPi.GPIO
   ●
   Broad use of RPi.GPIO
   – Used in Raspberry Pi learning resources
   – 132k code search results on github.com
   ●
   Lots of typing required for basic examples
   ●
   Lots of copy/paste code when using more complicated devices
   like sensors
   ●
   Requires fundamental understanding of electronics
   ●
   Lots of use of polling
   ●
   Implementation in C – exposes a non-Pythonic API
   

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5. sudo
   ●
   In Raspbian Wheezy, root access was needed to access the
   GPIO pins
   ●
   This meant running Python files with sudo
   ●
   This also meant opening IDLE from the menu did not allow
   GPIO access, must be opened with sudo idle &
   ●
   The pi user was given access to GPIO pins in Raspbian Jessie
   (released during development of GPIO Zero)
   

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6. Motivation
   ●
   CamJam talk 12/9/15 - How to build Python APIs for
   Raspberry Pi Hardware
   ●
   Teachers saying it's too hard to use Python
   ●
   Too much code to write to flash an LED (what is this, Java?)
   ●
   Too much boilerplate code needed to get started
   ●
   Too many electronics concepts required to understand (or
   ignore) e.g. pull-up vs. pull-down, and falling/rising edge
   ●
   Lots of bad code out there – all being copied
   

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7. Inspiration
   ●
   Python libraries for Pimoroni add-on boards
   ●
   Community users like Martin O'Hanlon commonly using LED
   class, etc.
   ●
   Picamera Python library
   ●
   Flotilla
   ●
   PyGame Zero – zero boilerplate wrapper for Pygame
   

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8. Intended audience
   ●
   Teachers
   ●
   Children
   ●
   Beginners
   ●
   Hobbyists
   

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9. GitHub
   

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10. GitHub Issues
    

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11. Google Doc
    

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12. 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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13. GPIO Zero
    from gpiozero import LED
    led = LED(17)
    led.blink()
    

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14. What do you think?
    

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15. A few minor observations...
    

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16. Hooked
    

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17. #4 Name?
    

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18. #4 Name?
    

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19. Eben, what do you think?
    

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20. Some initial comments
    ●
    “You're making it too easy”
    ●
    “Part of the fun is learning how it works”
    ●
    “It shouldn't be this easy to blink an LED”
    ●
    “You're dumbing down the flexibility of RPi.GPIO”
    ●
    “It's nice but I'll still use RPi.GPIO for the complex stuff”
    

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21. More initial comments
    ●
    “I'll have one of those. Can you get it ready for the next
    Raspbian release?” - Eben Upton
    ●
    “It's great! I never meant for RPi.GPIO to be an end-user library
    anyway!” - Ben Croston
    

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22. CamJam EduKit
    ●
    £5 starter kit (kit 1)
    ●
    £7 sensors kit (kit 2)
    ●
    £17 robotics kit (kit 3)
    ●
    Free worksheets
    ●
    Very reusable
    

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23. CamJam Kit 1 – starter kit
    ●
    Components:
    – LEDs
    – Buzzer
    – Button
    ●
    Recipes:
    – Flash LED
    – Traffic lights sequence
    ●
    + Button
    ●
    + Buzzer
    – Reaction game
    – Morse Code
    

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24. LED
    from gpiozero import LED
    from time import sleep
    led = LED(17)
    led.on() # on
    led.off() # off
    led.toggle() # on­>off or off­>on
    led.blink() # flash on/off continuously
    

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25. Buzzer
    from gpiozero import Buzzer
    from time import sleep
    buzzer = Buzzer(18)
    buzzer.on() # on
    buzzer.off() # off
    buzzer.toggle() # on­>off or off­>on
    buzzer.beep() # beep on/off continuously
    

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26. Button polling (pull-up) – RPi.GPIO
    GPIO.setup(4, GPIO.IN, GPIO.PUD_UP)
    while True:
    if not GPIO.input(4):
    print(“Pressed”)
    

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27. Button polling (pull-down) – RPi.GPIO
    GPIO.setup(4, GPIO.IN, GPIO.PUD_DOWN)
    while True:
    if GPIO.input(4):
    print(“Pressed”)
    

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28. Button polling (pull-up) – GPIO Zero
    button = Button(4)
    while True:
    if button.is_pressed:
    print(“Pressed”)
    

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29. Button polling (pull-down) – GPIO Zero
    button = Button(4, pull_up=False)
    while True:
    if button.is_pressed:
    print(“Pressed”)
    

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30. Button wait_for_edge (pull-up) – RPi.GPIO
    GPIO.setup(4, GPIO.IN, GPIO.PUD_UP)
    while True:
    GPIO.wait_for_edge(4, GPIO.FALLING)
    print(“Pressed”)
    

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31. Button wait_for_edge (pull-down) – RPi.GPIO
    GPIO.setup(4, GPIO.IN, GPIO.PUD_DOWN)
    while True:
    GPIO.wait_for_edge(4, GPIO.RISING)
    print(“Pressed”)
    

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32. Button wait_for_press (pull-up) – GPIO Zero
    button = Button(4)
    while True:
    button.wait_for_press()
    print(“Pressed”)
    

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33. Button wait_for_press (pull-down) – GPIO Zero
    button = Button(4, pull_up=False)
    while True:
    button.wait_for_press()
    print(“Pressed”)
    

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34. Button callback – RPi.GPIO
    GPIO.setup(4, GPIO.IN, GPIO.PUD_UP)
    def pressed(pin):
    print(“Pressed”)
    GPIO.add_event_detect(4, GPIO.FALLING, pressed)
    

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35. Button callback – GPIO Zero
    button = Button(4)
    def pressed():
    print(“Pressed”)
    button.when_pressed = pressed
    

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36. Button callback – RPi.GPIO
    GPIO.setup(4, GPIO.IN, GPIO.PUD_UP)
    def pressed(pin):
    print(“Pin %s Pressed” % pin)
    GPIO.add_event_detect(4, GPIO.FALLING, pressed)
    

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37. Button callback – GPIO Zero
    button = Button(4)
    def pressed(button):
    print(“Pin %s pressed” % button.pin)
    button.when_pressed = pressed
    

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38. Button + LED
    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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39. GPIO Music Box
    from gpiozero import Button
    import pygame.mixer
    from pygame.mixer import Sound
    pygame.mixer.init()
    sound_pins = {
    2: Sound("samples/drum_tom_mid_hard.wav"),
    3: Sound("samples/drum_cymbal_open.wav"),
    }
    buttons = [Button(pin) for pin in sound_pins]
    for button in buttons:
    sound = sound_pins[button.pin]
    button.when_pressed = sound.play
    

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40. LED – PWM – RPi.GPIO
    GPIO.setup(17, GPIO.OUT) # pin 17
    p = GPIO.PWM(17, 100) # pin 17, frequency 100Hz
    p.start(0) # initial duty cycle
    for i in range(101):
    p.ChangeDutyCycle(i)
    sleep(0.01)
    

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41. LED – PWM – GPIO Zero
    from gpiozero import PWMLED
    led = PWMLED(17)
    led.on() # on
    led.off() # off
    led.value = 0.5 # half brightness
    

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42. Full colour LED
    from gpiozero import RGBLED
    led = RGBLED(red=2, green=3, blue=4)
    led.red.on() # full red
    led.color = (1, 0, 1) # purple
    led.blue = 0.3 # dim the blue value to 0.3
    # now (1, 0, 0.3)
    

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43. Traffic Lights
    from gpiozero import TrafficLights
    lights = TrafficLights(9, 10, 11)
    lights.on() # all on
    lights.off() # all off
    lights.red.on() # red on
    lights.toggle() # swap state of all lights
    

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44. Traffic Lights sequence
    lights.green.on()
    lights.amber.off()
    lights.red.off()
    while True:
    sleep(10)
    lights.green.off()
    lights.amber.on()
    sleep(1)
    lights.amber.off()
    lights.red.on()
    sleep(10)
    lights.amber.on()
    sleep(1)
    lights.green.on()
    lights.amber.off()
    lights.red.off()
    

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45. TrafficHat
    from gpiozero import TrafficHat
    th = TrafficHat()
    th.lights.red.on()
    th.lights.amber.on()
    th.button.when_pressed = th.on
    th.button.when_released = th.off
    

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46. TrafficHat - PWM
    from gpiozero import TrafficHat
    th = TrafficHat(pwm=True)
    th.lights.red.value = 0.2
    th.lights.amber.value = 0.4
    th.lights.green.value = 0.8
    

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47. CamJam Kit 2 - sensors
    ●
    Components:
    – LEDs
    – Buzzer
    – Motion Sensor
    – Light Sensor
    – Temperature Sensor
    ●
    Recipes:
    – High/low temperature
    triggers LEDs
    – Light/dark triggers LEDs
    – Alarm – motion triggers
    buzzer
    

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48. Motion sensor
    from gpiozero import LED, MotionSensor
    led = LED(2)
    sensor = MotionSensor(3)
    sensor.when_motion = led.on
    sensor.when_no_motion = led.off
    

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49. Light sensor
    from gpiozero import LED, LightSensor
    led = LED(2)
    sensor = LightSensor(3)
    while True:
    sensor.wait_for_light()
    print("It's light!")
    sensor.wait_for_dark()
    print("It's dark")
    

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50. Temperature sensor
    ●
    w1thermsensor library exists
    ●
    Yet to be implemented in GPIO Zero compatible style
    

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51. CamJam Kit 3 - robot
    ●
    Components:
    – Motor Controller Board
    – Motors
    – Ultrasonic Sensor
    – Line Sensor
    ●
    Recipes:
    – Driving and turning
    – Line follower
    – Obstacle avoidance
    – Add a camera
    

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52. Motor
    from gpiozero import Motor
    from time import sleep
    motor = Motor(forward=17, backward=18)
    while True:
    motor.forward()
    sleep(5)
    motor.backward()
    sleep(5)
    

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53. Robot
    from gpiozero import Robot
    from time import sleep
    robot = Robot(left=(17, 18), right=(22, 23))
    while True:
    robot.forward()
    sleep(10)
    robot.left()
    sleep(1)
    

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54. Pre-configured robot interfaces
    robot = RyanteckRobot()
    robot = CamJamKitRobot()
    

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55. Button controlled Robot
    from gpiozero import RyanteckRobot, Button
    robot = RyanteckRobot()
    left = Button(26)
    right = Button(16)
    fw = Button(21)
    bw = Button(20)
    fw.when_pressed = robot.forward
    fw.when_released = robot.stop
    left.when_pressed = robot.left
    left.when_released = robot.stop
    right.when_pressed = robot.right
    right.when_released = robot.stop
    bw.when_pressed = robot.backward
    bw.when_released = robot.stop
    

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56. Push button stop motion
    from gpiozero import Button
    from picamera import PiCamera
    button = Button(4)
    with PiCamera() as camera:
    camera.start_preview()
    frame = 1
    while True:
    button.wait_for_press()
    camera.capture('/home/pi/frame%03d.jpg' % frame)
    frame += 1
    

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57. Analogue - potentiometers
    from gpiozero import MCP3008
    pot = MCP3008()
    while True:
    print(pot.value)
    

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58. Dial up the brightness!
    from gpiozero import PWMLED, MCP3008
    led = PWMLED(2)
    pot = MCP3008()
    while True:
    led.value = pot.value
    

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59. Analogue - potentiometers
    from gpiozero import RGBLED, MCP3008
    led = RGBLED(red=2, green=3, blue=4)
    red_pot = MCP3008(channel=0)
    green_pot = MCP3008(channel=1)
    blue_pot = MCP3008(channel=2)
    while True:
    led.red = red_pot.value
    led.green = green_pot.value
    led.blue = blue_pot.value
    

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60. #76 while True: led.red = pot.value
    

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61. #76 while True: led.red = pot.value
    

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62. #76 while True: led.red = pot.value
    

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63. #76 while True: led.red = pot.value
    

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

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65. Analogue - potentiometers
    from gpiozero import RGBLED, MCP3008
    led = RGBLED(red=2, green=3, blue=4)
    red_pot = MCP3008(channel=0)
    green_pot = MCP3008(channel=1)
    blue_pot = MCP3008(channel=2)
    led.red.source = red_pot.values
    led.green.source = green_pot.values
    led.blue.source = blue_pot.values
    

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66. Custom value generators
    blue = PWMLED(16)
    blue.source = [i / 10000.0 for i in range(10000)]
    red = PWMLED(12)
    red.source = blue.values
    blue.source = [i / 10000.0 for i in range(10000)]
    sensor = LightSensor(18)
    blue.source = sensor.values
    

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67. Custom value generators
    def read_slowly(iterable):
    for i in iterable:
    yield i
    sleep(0.1)
    red.source = read_slowly(blue.values)
    blue.source = read_slowly(sensor.values)
    

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68. Custom value generators
    button.when_pressed = led.on
    button.when_released = led.off
    led.source = button.values
    

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69. GPIO Zero Timeline
    ●
    12 Sept – CamJam talk sparked idea
    ●
    14 Sept – Initial commit on GitHub
    ●
    15 Sept – Named GPIO Zero, first PR, first alpha released on PyPi
    ●
    23 Sept – Mentioned in talk at PyConUK
    ●
    28 Sept – v0.6 public beta 1
    ●
    09 Oct – v0.7 public beta 2
    ●
    16 Oct – v0.8 public beta 3
    ●
    25 Oct – v0.9 public beta 4
    ●
    29 Oct – Featured in The MagPi
    ●
    16 Nov – v1.0 released
    ●
    21 Nov – Released in Raspbian Jessie
    

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70. v1.0
    ●
    ~200 commits
    ●
    2 contributors (+4 minor contributions)
    ●
    103 GitHub issues (53 issues, 50 PRs)
    ●
    4 alpha releases
    ●
    4 beta releases
    ●
    68 days between initial commit and major release
    

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71. Future development
    ●
    Add more components
    ●
    Integrate more add-ons
    ●
    Add test suite
    ●
    Replace RPi.GPIO dependency
    ●
    Promote use of “gpiozero standard” to allow other modules to
    provide objects which plug-in to gpiozero objects easily (e.g.
    source/values)
    

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72. What have I learned?
    ●
    Issue-driven development works really well
    ●
    Dave Jones is awesome (ok I already knew that)
    ●
    User-focused API design is important
    ●
    Getting feedback from teachers is hard
    ●
    Getting code contributions is hard
    ●
    Getting documentation contributions is easier
    

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73. Install GPIO Zero
    ●
    Pre-installed in Raspbian Jessie since November
    ●
    Update with:
    sudo apt­get update
    ●
    Install with:
    sudo apt­get install python3­gpiozero
    or:
    sudo apt­get install python­gpiozero
    

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74. GPIO Zero
    ●
    www.pythonhosted.org/gpiozero
    – Installation instructions
    – Documentation
    – Examples
    ●
    GitHub Issues
    – Suggestions
    – Feedback
    ●
    Contact me
    – ben@raspberrypi.org
    – @ben_nuttall on Twitter
    ●
    #gpiozero on Twitter
    

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75. Zero all the things!
    ●
    Raspberry Pi Zero
    ●
    PyGame Zero
    ●
    GPIO Zero
    

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76. GPIO Zero:
    Developing a friendly Python API
    for physical computing
    Ben Nuttall
    Raspberry Pi Foundation
    UK Charity 1129409
    

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