Python library to interact with Move Hub

Move Hub is central controller block of LEGO® Boost Robotics Set.

In fact, Move Hub is just Bluetooth hardware, all manipulations are done with commands passed through Bluetooth Low Energy (BLE) wireless protocol. One of ways to issue these commands is to write Python program using this library.

Best way to start is to look into demo.py file, and run it (assuming you have installed library).

If you have Vernie assembled, you might run scripts from examples/vernie directory.

Demonstrational Videos

Features

• auto-detect and connect to Move Hub device
• auto-detects peripheral devices connected to Hub
• constant, angled and timed movement for motors, rotation sensor subscription
• vision sensor: several modes to measure distance, color and luminosity
• tilt sensor subscription: 2 axis, 3 axis, bump detect modes
• RGB LED color change
• push button status subscription
• battery voltage and current subscription available
• permanent Bluetooth connection server for faster debugging

Usage

Please note that this library requires one of Bluetooth backend libraries to be installed, please read section here for details.

Install library like this:

pip install https://github.com/undera/pylgbst/archive/1.1.0.tar.gz

Then instantiate MoveHub object and start invoking its methods. Following is example to just print peripherals detected on Hub:

from pylgbst.hub import MoveHub

hub = MoveHub()

for device in hub.peripherals:
    print(device)

Each peripheral kind has own methods to do actions and/or get sensor data. See features list for individual doc pages.

Bluetooth Backend Prerequisites

You have following options to install as Bluetooth backend:

• pip install pygatt - pygatt lib, works on both Windows and Linux
• pip install gatt - gatt lib, supports Linux, does not work on Windows
• pip install gattlib - gattlib - supports Linux, does not work on Windows, requires sudo
• pip install bluepy - bluepy lib, supports Linux, including Raspbian, which allows connection to the hub from the Raspberry PI

Running on Windows requires Bluegiga BLED112 Bluetooth Smart Dongle hardware piece, because no other hardware currently works on Windows with Python+BLE.

Please let author know if you have discovered any compatibility/preprequisite details, so we will update this section to help future users

Depending on backend type, you might need Linux sudo to be used when running Python.

Bluetooth Connection Options

There is optional parameter for MoveHub class constructor, accepting instance of Connection object. By default, it will try to use whatever get_connection_auto() returns. You have several options to manually control that:

• use pylgbst.get_connection_auto() to attempt backend auto-choice, autodetect uses
• use BlueGigaConnection() - if you use BlueGiga Adapter (pygatt library prerequisite)
• use GattConnection() - if you use Gatt Backend on Linux (gatt library prerequisite)
• use GattoolConnection() - if you use GattTool Backend on Linux (pygatt library prerequisite)
• use GattLibConnection() - if you use GattLib Backend on Linux (gattlib library prerequisite)
• use BluepyConnection() - if you use Bluepy backend on Linux/Raspbian (bluepy library prerequisite)
• pass instance of DebugServerConnection if you are using Debug Server (more details below).

All the functions above have optional arguments to specify adapter name and MoveHub mac address. Please look function source code for details.

If you want to specify name for Bluetooth interface to use on local computer, you can pass that to class or function of getting a connection. Then pass connection object to MoveHub constructor. Like this:

from pylgbst.hub import MoveHub
from pylgbst.comms.cgatt import GattConnection

conn = GattConnection("hci1")
conn.connect()  # you can pass Hub mac address as parameter here, like 'AA:BB:CC:DD:EE:FF'

hub = MoveHub(conn)

Debug Server

Running debug server opens permanent BLE connection to Hub and listening on TCP port for communications. This avoids the need to re-start Hub all the time.

There is DebugServerConnection class that you can use with it, instead of BLEConnection.

Starting debug server is done like this (you may need to run it with sudo, depending on your BLE backend):

python -c "import logging; logging.basicConfig(level=logging.DEBUG); \
                import pylgbst; pylgbst.start_debug_server()"

Then push green button on MoveHub, so permanent BLE connection will be established.

Roadmap & TODO

• validate operations with other Hub types (train, PUP etc)
• make connections to detect hub by UUID instead of name
• document all API methods
• make debug server to re-establish BLE connection on loss

Links

• https://github.com/LEGO/lego-ble-wireless-protocol-docs - true docs for LEGO BLE protocol
• https://github.com/JorgePe/BOOSTreveng - initial source of protocol knowledge
• https://github.com/nathankellenicki/node-poweredup - JavaScript version of library
• https://github.com/spezifisch/sphero-python/blob/master/BB8joyDrive.py - example with another approach to bluetooth libs