ofxMyoWebSockets

An openFrameworks addon for working with Myo armbands from Thalmic Labs over the built-in WebSocket interface that is part of the Myo Connect background application from Thalmic.

Example

See the included example project. In brief:

class ofApp : public ofBaseApp{
public:
    ofxMyoWebSockets::Connection myo;
};

void ofApp::setup(){
    // pass in a bool for auto-reconnect
    myo.connect(true);
}

void ofApp::update(){
    myo.update();
}

void ofApp::draw(){

    ofDrawBitmapStringHighlight("Connected bands: " + ofToString(myo.numConnectedArmbands()), 20, 20);

    float angle; ofVec3f axis;
    for (int i = 0; i < myo.numConnectedArmbands(); i++) {

        ofxMyoWebSockets::Armband* armband = myo.armbands[i];

        cam.begin();
        ofDrawGrid(250, 5);

        ofVec3f pos = armband->quat * ofVec3f(300, 0, 0);
        ofDrawArrow( ofVec3f(0, 0, 0), pos, 8 );

        cam.end();

    }
}

Features

Multiple Myo Armbands

This addon supports multiple armbands. The current limitation is the Myo Connect background application, which only supports two. If Myo Connect is updated, this addon should automatically support additional armbands.

You only need to create one instance of ofxMyoWebSockets::Connection. Each armband should be referenced by its ID assigned from Myo Connect, which can be accessed at ofxMyoWebSockets::Armband::id.

Event Notification

Data and events from the websocket stream are relayed using the openFrameworks notification system. Register for events you care about in your app's setup method:

ofAddListener(myo.connectedEvent, this, &ofApp::myoConnected);
ofAddListener(myo.poseConfirmedEvent, this, &ofApp::poseConfirmed);
ofAddListener(myo.orientationEvent, this, &ofApp::orientation);

Make sure to declare your callbacks in your app's header file:

void myoConnected(ofxMyoWebSockets::Armband& armband);
void poseConfirmed(ofxMyoWebSockets::Armband& armband);
void orientation(ofxMyoWebSockets::Armband& armband);

And handle them like so:

void ofApp::poseConfirmed(ofxMyoWebSockets::Armband& armband){
    if (armband.pose == "wave_out") {
        ofLogNotice() << "Hi!";
    }
}

See the WebSocket interface specification and look in the ofxMyoWebSockets.h header file for a full list of events.

Pinky-to-Thumb Unlock

Enable this if you'd like to require this hand pose to be performed before other hand poses are recognized.

myo.setRequiresUnlock(true);

Unlock Timeout

You can set how long the unlocked state will last by calling the following method. The current default is 3 seconds.

myo.setUnlockTimeout(5.0);

Lock After Pose

Armbands can be set back to being locked immediately following a recognized hand pose, requiring the pinky-to-thumb pose again in order to prevent accidental input.

myo.setLockAfterPose(true);

Pose Confirmatin/Minimum Gesture Duration

You can set a minimum time that a pose most be held before it is recognized. This is useful if you want to wave out for 1 second before triggering a pose to prevent accidental input. The current default is 0.5 seconds.

myo.setMinimumGestureDuration(1.0);

To disable, simply pass in a duration of 0:

myo.setMinimumGestureDuration(0.0);

Use Degrees or Radians

Roll, pitch, and yaw values are automatically calculated based on the stored quaternion value. By default, these values are represented in radians. If you'd prefer to work in degrees, just call the following method:

myo.setUseDegrees(true);

Dependencies

• ofxLibwebsockets from the LAB at Rockwell
• ofxJSON from Jeff Crouse