Prime Hub / Inventor Hub

../_images/primeinventorhub.png
class InventorHub

This class is the same as the PrimeHub class, shown below. Both classes work on both hubs.

These hubs are completely identical. They use the same Pybricks firmware.

class PrimeHub(top_side=Axis.Z, front_side=Axis.X)

LEGO® SPIKE Prime Hub or LEGO® MINDSTORMS Inventor Hub.

Initializes the hub. Optionally, specify how the hub is placed in your design by saying in which direction the top side (with the buttons) and front side (with the USB port) are pointing.

Parameters
  • top_side (Axis) – The axis that passes through the top side of the hub.

  • front_side (Axis) – The axis that passes through the front side of the hub.

Using the hub status light

../_images/primehub_light_label.png
light.on(color)

Turns on the light at the specified color.

Parameters

color (Color) – Color of the light.

light.off()

Turns off the light.

Blinks the light at a given color by turning it on and off for given durations.

The light keeps blinking indefinitely while the rest of your program keeps running.

This method provides a simple way to make basic but useful patterns. For more generic and multi-color patterns, use animate() instead.

Parameters
  • color (Color) – Color of the light.

  • durations (list) – List of (time: ms) values of the form [on_1, off_1, on_2, off_2, ...].

light.animate(colors, interval)

Animates the light with a list of colors. The next color in the list is shown after the given interval.

The animation runs in the background while the rest of your program keeps running. When the animation completes, it repeats.

Parameters
  • colors (list) – List of Color values.

  • interval (time: ms) – Time between color updates.

Using the light matrix display

../_images/primehub_display_label.png
display.orientation(up)

Sets the orientation of the light matrix display.

Only new displayed images and pixels are affected. The existing display contents remain unchanged.

Parameters

top (Side) – Which side of the light matrix display is “up” in your design. Choose Side.TOP, Side.LEFT, Side.RIGHT, or Side.BOTTOM.

display.off()

Turns off all the pixels.

display.pixel(row, column, brightness=100)

Turns on one pixel at the specified brightness.

Parameters
  • row (int) – Vertical grid index, starting at 0 from the top.

  • column (int) – Horizontal grid index, starting at 0 from the left.

  • brightness (brightness: %) – Brightness of the pixel.

display.image(matrix)

Displays an image, represented by a matrix of brightness: % values.

Parameters

matrix (Matrix) – Matrix of intensities (brightness: %). A 2D list is also accepted.

display.animate(matrices, interval)

Displays an animation made using a list of images.

Each image has the same format as above. Each image is shown for the given interval. The animation repeats forever while the rest of your program keeps running.

Parameters
  • matrix (list) – List of Matrix of intensities.

  • interval (time: ms) – Time to display each image in the list.

display.number(number)

Displays a number in the range -99 to 99.

A minus sign (-) is shown as a faint dot in the center of the display. Numbers greater than 99 are shown as >. Numbers less than -99 are shown as <.

Parameters

number (int) – The number to be displayed.

display.char(char)

Displays a character or symbol on the light grid. This may be any letter (az), capital letter (AZ) or one of the following symbols: !"#$%&'()*+,-./:;<=>?@[\]^_`{|}.

Parameters

character (str) – The character or symbol to be displayed.

display.text(text, on=500, off=50)

Displays a text string, one character at a time, with a pause between each character. After the last character is shown, all lights turn off.

Parameters
  • text (str) – The text to be displayed.

  • on (time: ms) – For how long a character is shown.

  • off (time: ms) – For how long the display is off between characters.

Using the buttons

../_images/primehub_buttons_label.png
buttons.pressed()

Checks which buttons are currently pressed.

Returns

Tuple of pressed buttons.

Return type

Tuple of Button

Using the IMU

imu.up()

Checks which side of the hub currently faces upward.

Returns

Side.TOP, Side.BOTTOM, Side.LEFT, Side.RIGHT, Side.FRONT or Side.BACK.

Return type

Side

imu.tilt()

Gets the pitch and roll angles. This is relative to the user-specified neutral orientation.

The order of rotation is pitch-then-roll. This is equivalent to a positive rotation along the robot y-axis and then a positive rotation along the x-axis.

Returns

Pitch and roll angles.

Return type

(angle: deg, angle: deg)

imu.acceleration(axis=None)

Gets the acceleration of the device along a given axis in the robot reference frame.

Parameters

axis (Axis) – Axis along which the acceleration is measured.

Returns

Acceleration along the specified axis. If you specify no axis, this returns a vector of accelerations along all axes.

Return type

linear acceleration: m/s/s

imu.angular_velocity(axis=None)

Gets the angular velocity of the device along a given axis in the robot reference frame.

Parameters

axis (Axis) – Axis along which the angular velocity is measured.

Returns

Angular velocity along the specified axis. If you specify no axis, this returns a vector of accelerations along all axes.

Return type

rotational speed: deg/s

imu.heading()

Gets the heading angle relative to the starting orientation. It is a a positive rotation around the z-axis in the robot frame, prior to applying any tilt rotation.

For a vehicle viewed from the top, this means that a positive heading value corresponds to a counterclockwise rotation.

Note

This method is not yet implemented.

Returns

Heading angle relative to starting orientation.

Return type

angle: deg

imu.reset_heading(angle)

Resets the accumulated heading angle of the robot.

Note

This method is not yet implemented.

Parameters

angle (angle: deg) – Value to which the heading should be reset.

Using the speaker

speaker.beep(frequency=500, duration=100)

Play a beep/tone.

Parameters
  • frequency (frequency: Hz) – Frequency of the beep. Frequencies below 100 are treated as 100.

  • duration (time: ms) – Duration of the beep. If the duration is less than 0, then the method returns immediately and the frequency play continues to play indefinitely.

speaker.play_notes(notes, tempo=120)

Plays a sequence of musical notes. For example: ['C4/4', 'C4/4', 'G4/4', 'G4/4'].

Each note is a string with the following format:

  • The first character is the name of the note, A to G or R for a rest.

  • Note names can also include an accidental # (sharp) or b (flat). B#/Cb and E#/Fb are not allowed.

  • The note name is followed by the octave number 2 to 8. For example C4 is middle C. The octave changes to the next number at the note C, for example, B3 is the note below middle C (C4).

  • The octave is followed by / and a number that indicates the size of the note. For example /4 is a quarter note, /8 is an eighth note and so on.

  • This can optionally followed by a . to make a dotted note. Dotted notes are 1-1/2 times as long as notes without a dot.

  • The note can optionally end with a _ which is a tie or a slur. This causes there to be no pause between this note and the next note.

Parameters
  • notes (iter) – A sequence of notes to be played.

  • tempo (int) – Beats per minute. A quarter note is one beat.

Using the battery

battery.voltage()

Gets the voltage of the battery.

Returns

Battery voltage.

Return type

voltage: mV

battery.current()

Gets the current supplied by the battery.

Returns

Battery current.

Return type

current: mA

System control

system.set_stop_button(button)

Sets the button or button combination that stops a running script.

Normally, the center button is used to stop a running script. You can change or disable this behavior in order to use the button for other purposes.

Parameters

Button – A button such as Button.CENTER, or a tuple of multiple buttons. Choose None to disable the stop button altogether.

system.name()

Gets the hub name. This is the name you see when connecting via Bluetooth.

Returns

The hub name.

Return type

str

system.shutdown()

Stops your program and shuts the hub down.

system.reset_reason()

Finds out how and why the hub (re)booted. This can be useful to diagnose some problems.

Returns

Returns 0 if the hub was previously powered off normally. Returns 1 if the hub rebooted automatically, like after a firmware update. Returns 2 if the hub previously crashed due to a watchdog timeout, which indicates a firmware issue.

Return type

int

Note

The examples below use the PrimeHub class. The examples work fine on both hubs because they are the identical. If you prefer, you can change this to InventorHub.

Status light examples

Turning the light on and off

from pybricks.hubs import PrimeHub
from pybricks.parameters import Color
from pybricks.tools import wait

# Initialize the hub.
hub = PrimeHub()

# Turn the light on and off 5 times.
for i in range(5):

    hub.light.on(Color.RED)
    wait(1000)

    hub.light.off()
    wait(500)

Changing brightness and using custom colors

from pybricks.hubs import PrimeHub
from pybricks.parameters import Color
from pybricks.tools import wait

# Initialize the hub.
hub = PrimeHub()

# Show the color at 30% brightness.
hub.light.on(Color.RED * 0.3)

wait(2000)

# Use your own custom color.
hub.light.on(Color(h=30, s=100, v=50))

wait(2000)

# Go through all the colors.
for hue in range(360):
    hub.light.on(Color(hue))
    wait(10)

Creating light animations

from pybricks.hubs import PrimeHub
from pybricks.parameters import Color
from pybricks.tools import wait
from umath import sin, pi

# Initialize the hub.
hub = PrimeHub()

# Make an animation with multiple colors.
hub.light.animate([Color.RED, Color.GREEN, Color.NONE], interval=500)

wait(10000)

# Make the color RED grow faint and bright using a sine pattern.
hub.light.animate(
    [Color.RED * (0.5 * sin(i / 15 * pi) + 0.5) for i in range(30)], 40)

wait(10000)

# Cycle through a rainbow of colors.
hub.light.animate([Color(h=i*8) for i in range(45)], interval=40)

wait(10000)

Matrix display examples

Displaying images

from pybricks.hubs import PrimeHub
from pybricks.tools import wait
from pybricks.parameters import Icon

# Initialize the hub.
hub = PrimeHub()

# Display a big arrow pointing up.
hub.display.image(Icon.UP)

# Wait so we can see what is displayed.
wait(2000)

# Display a heart at half brightness.
hub.display.image(Icon.HEART / 2)

# Wait so we can see what is displayed.
wait(2000)

Displaying numbers

from pybricks.hubs import PrimeHub
from pybricks.tools import wait

# Initialize the hub.
hub = PrimeHub()

# Count from 0 to 99.
for i in range(100):
    hub.display.number(i)
    wait(200)

Displaying text

from pybricks.hubs import PrimeHub
from pybricks.tools import wait

# Initialize the hub.
hub = PrimeHub()

# Display the letter A for two seconds.
hub.display.char('A')
wait(2000)

# Display text, one letter at a time.
hub.display.text('Hello, world!')

Displaying individual pixels

from pybricks.hubs import PrimeHub
from pybricks.tools import wait

# Initialize the hub.
hub = PrimeHub()

# Turn on the pixel at row 1, column 2.
hub.display.pixel(1, 2)
wait(2000)

# Turn on the pixel at row 2, column 4, at 50% brightness.
hub.display.pixel(2, 4, 50)
wait(2000)

# Turn off the pixel at row 1, column 2.
hub.display.pixel(1, 2, 0)
wait(2000)

Changing the display orientation

from pybricks.hubs import PrimeHub
from pybricks.tools import wait
from pybricks.parameters import Side

# Initialize the hub.
hub = PrimeHub()

# Rotate the display. Now right is up.
hub.display.orientation(up=Side.RIGHT)

# Display a number. This will be shown sideways.
hub.display.number(23)

# Wait so we can see what is displayed.
wait(10000)
from pybricks.hubs import PrimeHub
from pybricks.parameters import Icon
from pybricks.tools import wait

# Initialize the hub.
hub = PrimeHub()

while True:

    # Check which side of the hub is up.
    up_side = hub.imu.up()

    # Use this side to set the display orientation.
    hub.display.orientation(up_side)

    # Display something, like an arrow.
    hub.display.image(Icon.UP)

    wait(10)

Making your own images

from pybricks.hubs import PrimeHub
from pybricks.tools import wait
from pybricks.geometry import Matrix

# Initialize the hub.
hub = PrimeHub()

# Make a square that is bright on the outside and faint in the middle.
SQUARE = Matrix([
    [100, 100, 100, 100, 100],
    [100, 50,  50,  50,  100],
    [100, 50,  0,   50,  100],
    [100, 50,  50,  50,  100],
    [100, 100, 100, 100, 100],
])

# Display the square.
hub.display.image(SQUARE)
wait(3000)

# Make an image using a Python list comprehension. In this image, the
# brightness of each pixel is the sum of the row and column index. So the
# light is faint in the top left and bright in the bottom right.
GRADIENT = Matrix([[(r + c) for c in range(5)] for r in range(5)]) * 12.5

# Display the generated gradient.
hub.display.image(GRADIENT)
wait(3000)

Combining images to make expressions

from pybricks.hubs import PrimeHub
from pybricks.parameters import Icon, Side
from pybricks.tools import wait

from urandom import randint

# Initialize the hub.
hub = PrimeHub()
hub.display.orientation(up=Side.RIGHT)

while True:

    # Start with random left brow: up or down.
    if randint(0, 100) < 70:
        brows = Icon.EYE_LEFT_BROW*0.5
    else:
        brows = Icon.EYE_LEFT_BROW_UP*0.5

    # Add random right brow: up or down.
    if randint(0, 100) < 70:
        brows += Icon.EYE_RIGHT_BROW*0.5
    else:
        brows += Icon.EYE_RIGHT_BROW_UP*0.5

    for i in range(3):
        # Display eyes open plus the random brows.
        hub.display.image(Icon.EYE_LEFT + Icon.EYE_RIGHT + brows)
        wait(2000)

        # Display eyes blinked plus the random brows.
        hub.display.image(Icon.EYE_LEFT_BLINK*0.7 + Icon.EYE_RIGHT_BLINK*0.7 + brows)
        wait(200)

Displaying animations

from pybricks.hubs import PrimeHub
from pybricks.parameters import Icon
from pybricks.tools import wait

# Initialize the hub.
hub = PrimeHub()

# Turn the hub light off (optional).
hub.light.off()

# Create a list of intensities from 0 to 100 and back.
brightness = list(range(0, 100, 4)) + list(range(100, 0, -4))

# Create an animation of the heart icon with changing brightness.
hub.display.animate([Icon.HEART * i/100 for i in brightness], 30)

# The animation repeats in the background. Here we just wait.
while True:
    wait(100)

Button examples

Detecting button presses

from pybricks.hubs import PrimeHub
from pybricks.parameters import Button, Icon
from pybricks.tools import wait

# Initialize the hub.
hub = PrimeHub()

# Wait for any button to be pressed, and save the result.
pressed = []
while not any(pressed):
    pressed = hub.buttons.pressed()
    wait(10)

# Display a circle.
hub.display.image(Icon.CIRCLE)

# Wait for all buttons to be released.
while any(hub.buttons.pressed()):
    wait(10)

# Display an arrow to indicate which button was pressed.
if Button.LEFT in pressed:
    hub.display.image(Icon.ARROW_LEFT_DOWN)
elif Button.RIGHT in pressed:
    hub.display.image(Icon.ARROW_RIGHT_DOWN)
elif Button.BLUETOOTH in pressed:
    hub.display.image(Icon.ARROW_RIGHT_UP)

wait(3000)

IMU examples

Testing which way is up

from pybricks.hubs import PrimeHub
from pybricks.parameters import Color, Side
from pybricks.tools import wait

# Initialize the hub.
hub = PrimeHub()

# Define colors for each side in a dictionary.
SIDE_COLORS = {
    Side.TOP: Color.RED,
    Side.BOTTOM: Color.BLUE,
    Side.LEFT: Color.GREEN,
    Side.RIGHT: Color.YELLOW,
    Side.FRONT: Color.MAGENTA,
    Side.BACK: Color.BLACK,
}

# Keep updating the color based on detected up side.
while True:

    # Check which side of the hub is up.
    up_side = hub.imu.up()

    # Change the color based on the side.
    hub.light.on(SIDE_COLORS[up_side])

    # Also print the result.
    print(up_side)
    wait(50)

Reading the tilt value

from pybricks.hubs import PrimeHub
from pybricks.tools import wait

# Initialize the hub.
hub = PrimeHub()

while True:
    # Read the tilt values.
    pitch, roll = hub.imu.tilt()

    # Print the result.
    print(pitch, roll)
    wait(200)

Using a custom hub orientation

from pybricks.hubs import PrimeHub
from pybricks.tools import wait
from pybricks.geometry import Axis

# Initialize the hub. In this case, specify that the hub is mounted with the
# top side facing forward and the front side facing to the right.
# For example, this is how the hub is mounted in BLAST in the 51515 set.
hub = PrimeHub(top_side=Axis.X, front_side=-Axis.Y)

while True:
    # Read the tilt values. Now, the values are 0 when BLAST stands upright.
    # Leaning forward gives positive pitch. Leaning right gives positive roll.
    pitch, roll = hub.imu.tilt()

    # Print the result.
    print(pitch, roll)
    wait(200)

Reading acceleration and angular velocity vectors

from pybricks.hubs import PrimeHub
from pybricks.tools import wait

# Initialize the hub.
hub = PrimeHub()

# Get the acceleration vector.
print(hub.imu.acceleration())

# Get the angular velocity vector.
print(hub.imu.angular_velocity())

# Wait so we can see what we printed
wait(5000)

Reading acceleration and angular velocity on one axis

from pybricks.hubs import PrimeHub
from pybricks.tools import wait
from pybricks.geometry import Axis

# Initialize the hub.
hub = PrimeHub()

# Get the acceleration or angular_velocity along a single axis.
# If you need only one value, this is more memory efficient.
while True:

    # Read the forward acceleration.
    forward_acceleration = hub.imu.acceleration(Axis.X)

    # Read the yaw rate.
    yaw_rate = hub.imu.angular_velocity(Axis.Z)

    # Print the yaw rate.
    print(yaw_rate)
    wait(100)

System examples

Changing the stop button combination

from pybricks.hubs import PrimeHub
from pybricks.parameters import Button

# Initialize the hub.
hub = PrimeHub()

# Configure the stop button combination. Now, your program stops
# if you press the center and Bluetooth buttons simultaneously.
hub.system.set_stop_button((Button.CENTER, Button.BLUETOOTH))

# Now we can use the center button as a normal button.
while True:

    # Play a sound if the center button is pressed.
    if Button.CENTER in hub.buttons.pressed():
        hub.speaker.beep()

Turning the hub off

from pybricks.hubs import PrimeHub
from pybricks.tools import wait

# Initialize the hub.
hub = PrimeHub()

# Say goodbye and give some time to send it.
print("Goodbye!")
wait(100)

# Shut the hub down.
hub.system.shutdown()