Example bluetooth hub to hub communication without motors or external sensors

[BertLindeman]

Just wanted to try the BLE communication in firmware v3.3.0b6,
but did not want to attach motors or other peripherals to the hub(s).

Used a hub with an IMU (Internal Motion sensor) as sender to simply show what side of the hub is the up-side.
The receiving hub(s) can be any hub as far as I know.
They just receive the data and set the Color of the system-led or central button Color.

Best to disconnect the hubs from the computer and start the program by pressing the hub button.
First start the sending hub and after that the receiving hub(s).

Best disconnect the hub(s) from the computer to get a good signal.
First start the sender hub by pressing the (central) button.

It's fun to watch them working together.

Example.pybricks.hub.to.hub.communication_9MB.mp4

BLE_receive_hub_only.py

# Observing data from other hubs
# Best transfer if NO bluetooth connection is active to the computer

from pybricks.hubs import ThisHub
# from pybricks.pupdevices import Motor
from pybricks.parameters import Color
from pybricks.tools import wait

# Initialize the hub (any hub supports observe_channels)
hub = ThisHub(observe_channels=[1])

# Define colors for each side in a dictionary based upon the digits received.
SIDE_COLORS_FROM_BLE = {
    0: Color.RED,
    1: Color.WHITE,
    2: Color.GREEN,
    3: Color.YELLOW,
    4: Color.MAGENTA,
    5: Color.CYAN,
}


while True:
    # Receive broadcast from the other hub.
    data = hub.ble.observe(1)
    # print(data, end=" ")

    if data is None:
        # No data has been received in the last 1 second.
        hub.light.on(Color.ORANGE)
    else:
        # Data was received and is less that one second old. (How to know how long ago???)
        # print("data 0", data[0])

        # *data* contains the same values in the same order
        # that were passed to hub.ble.broadcast() on the
        # other hub.

        hub.light.on(SIDE_COLORS_FROM_BLE[data[0]])
        # print("data 0", data[0], "data 1", data[1])

    # Broadcasts are only sent every 100 milliseconds, so there is
    # no reason to call the observe() method more often than that.
    wait(100)

BLE_broadcast_hub_only.py

# Broadcasting data to other hubs
# Best transfer if NO bluetooth connection is active to the computer

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


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

# Define digits to transmit for the colors for each side in a dictionary.
SIDE_NUM = {
    Side.TOP: 0,
    Side.BOTTOM: 1,
    Side.LEFT: 2,
    Side.RIGHT: 3,
    Side.FRONT: 4,
    Side.BACK: 5,
}

# Initialize the hub.
hub = ThisHub(broadcast_channel=1)


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])

    # Set the broadcast data and start broadcasting if not already doing so.
    hub.ble.broadcast(SIDE_NUM[up_side])

    # Broadcasts are only sent every 100 milliseconds, so there is no reason
    # to call the broadcast() method more often than that.
    wait(100)

[laurensvalk]

Thanks for sharing this! The video is a great demo too. I've shared it online on our channels, hope that's OK!

[BertLindeman]

Laurens, you know that;s OK 😉