Background

MioConnect is a MyoConnect alternative for the Myo Armband, connects to the device(s) and transmits EMG/IMU via OSC.

This software was developed for the Emovere Project (http://www.emovere.cl/). They needed to avoid MyoConnect, because they only required raw EMG/IMU data during a contemporary dance performance, and could not re-sync the armband after sudden arm movements.

The code provides a comprehensible framework for a direct connection to the Myo Armband, using the Bluegiga BLE Bluetooth library and the Myo Bluetooth Protocol released by Thalmic Labs on March 26, 2015. Hopefully this helps a lot of people developing their own direct connections and understanding the bluetooth protocol.

Requirements

This project runs on Python 3. Requirements are inside requirements.txt file.

• pyserial
• python-osc

You can easily install them via pip install -r requirements.txt.

How to run

The file mio_connect.py contains the main loop for the application. Which instantiates a MyoDriver object and starts the main procedure.

Run mio_connect.py -h to get help on the software usage. You can add the following commands:

• -h or --help to see this list
• -s or --shutdown to turn off (deep sleep) the expected amount of myos
• -n <amount> or --nmyo <amount> to set the amount of devices to expect
• -a <address> or --address <address> to set OSC address
• -p <port_number> or --port <port_number> to set OSC port
• -v or --verbose for verbose output

Default configuration is written in a single file: src/config.py. These settings include:

• MYO_AMOUNT: Default amount of myos to detect
• EMG_MODE: EMG mode (send data, raw data, disabled, ...)
• IMU_MODE: IMU mode (send data, send events, disabled, ...)
• CLASSIFIER_MODE: Classifier mode (enabled, disabled)
• DEEP_SLEEP_AT_KEYBOARD_INTERRUPT: Turn off (deep sleep) at KeyboardInterrupt
• PRINT_EMG: Print EMG/IMU through console
• PRINT_IMU: Verbose output
• GET_MYO_INFO: Store and notify Myo Info after connections are made
• MESSAGE_DELAY: Added delay between messages sent to the armband
• RETRY_CONNECTION_AFTER: Time to wait before retrying the connection after unexpected disconnect
• MAX_RETRIES: Maximum amount of retries before giving up

What it does

The code is thoroughly documented and should be easy to follow, but a high-level description will be given:

• Sends a disconnect message in case some connections have persisted a previous connection
• Add handlers for every expected bluetooth event
• Starts a connection procedure for every expected armband
  • Discover devices
  • Find Myos
  • Establish a direct connection
  • Await answer for every critical event
  • Disable sleep
  • Start EMG/IMU/Classifier according to config file
  • Subscribe to EMG/IMU/Classifier events
• set_handlers method shows how every received message is handled. handle_imu and handle_emg are critical parts, in which the OSC protocol is implemented
• An infinite loop lets the application listen for events
• A keyboard interrupt (Ctrl+C) will trigger disconnect messages and end the program

If a myo disconnects, an event is received and a reconnection routine will start with provided configuration.

Project files

mio_connect.py

This file contains the main loop for the application.

src

Each file contains a single python class with its own responsibility:

• bluetooth.py / Bluetooth(msg_delay): Serial communication and command encapsulation. Every command sent to the armband should pass through this class. New commands can be added at the end of the command section, following the structure of the other commands and reading the myohw file (the .py or the official one).

• config.py / Config(): Settings for the application. Details under "How to run" section.

• data_handler.py / DataHandler(config_obj): Handles EMG/IMU data and sends it through OSC. Here lies encapsulated the OSC message structure and no other file should change when adjusting it.

• myo.py / Myo(address): Class for a myo, handles device info and prints it nicely. It's instantiated after the address is received, and it's used inside handlers in order to properly connect/reconnect. It also keeps the data obtained through MyoDriver's method get_info() (i.e. device name, battery level and firmware version), printing a Myo object will display all the info.

• myodriver.py / MyoDriver(config_obj): Driver for myo connection and data handling. Implements main procedures for global functionality, such as connection and reconnection protocols and data/event handling.

src/public

Contains files that are taken from another project following their respective licenses.

• bglib.py: BGLib implementations for Bluegiga BLE112 Bluetooth Smart module.

• myohw.py: A partial transcription of myohw.h file released by Thalmic Labs Inc.

Turn off Myo

The protocol provides the deep_sleep command (see myohw), according to the release notes, the armband will go into a state with basically everything off and can stay in that state for months. The only way to turn it back on is plugging it via USB (as MyoConnect would).

You can start a procedure for finding devices and the turning them all off with the -s (--shutdown) command. Using it with -n <amount> will find and turn off given amount of myos.

Issues

• Not tested on Linux or OS X, but should work the same way.
• There's currently no way to enter Dongle name manually, if anything goes wrong, you should hardcode it at serial initialization.
• No user interface.
• Does not subscribe to Classifier events.

Thalmic Labs rebrand

Thalmic Labs is no longer selling Myo Armbands and has their website (https://www.myo.com/) is now unreachable. The developer forums (https://developer.thalmic.com/forums/) are also down and we should not expect any future support from Thalmic, but the community may gather in another website (maybe https://www.reddit.com/r/thalmic/)

This is actually a rebrand, they have become "North" and released Smart Glasses powered by Alexa (website: https://www.bynorth.com/).

Details here https://venturebeat.com/2018/10/23/thalmic-labs-rebrands-as-north-launches-999-alexa-powered-holographic-glasses/.

References

• Myo Bluetooth Protocol Release https://developerblog.myo.com/myo-bluetooth-spec-released/ Released by Thalmic Labs (2015).

• MyoStream https://github.com/hcilab/MyoStream Its README.md file has an excellent explanation of the bluetooth protocol.

• MyOSC https://github.com/benkuper/MyOSC OSC bridge for Myo.

• BGLib https://github.com/jrowberg/bglib BGLib implementations for Bluegiga BLE112 Bluetooth Smart module.

• About Thalmic Labs rebrand https://venturebeat.com/2018/10/23/thalmic-labs-rebrands-as-north-launches-999-alexa-powered-holographic-glasses/