Accelerometer Data

maryfertg · April 2016

Hi I need to work with 3 accelerometer axes of metawear. Now I am using only x axes but dont fix. Someone can help me please. I attach the code.

Adding, Can I compare, plus, sustract the values of the axes for example (x axes value - y axes value) or something like that? How have I manage the adquisition of data?

Code:

        findViewById(R.id.start_accel).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                accelModule.enableAxisSampling();
                accelModule.start();
            }
        });
    @Override
    public void onServiceConnected(ComponentName name, IBinder service) {
        serviceBinder = (MetaWearBleService.LocalBinder) service;
        String mwMacAddress="C3:DA:B6:74:FF:05";
        BluetoothManager btManager=(BluetoothManager)getSystemService(BLUETOOTH_SERVICE);
        BluetoothDevice btDevice=btManager.getAdapter().getRemoteDevice(mwMacAddress);

        mwBoard=serviceBinder.getMetaWearBoard(btDevice);
        mwBoard.setConnectionStateHandler(new MetaWearBoard.ConnectionStateHandler() {
            @Override
            public void disconnected() {
                Log.i(LOG_TAG,"Disconnected");
            }

            @Override
            public void connected() {
                Log.i(LOG_TAG, "Connected");
                try {

                    accelModule=mwBoard.getModule(Accelerometer.class);
                    accelModule.setOutputDataRate(50f);
                    accelModule.setAxisSamplingRange((float) 2);
                    accelModule.routeData().fromXAxis()
                            .process(new Sample(sampleSize))
                            .process(X_DATA,new Passthrough(Passthrough.Mode.COUNT,(short) 0))
                            .stream(X_DATA)
                            .process(new Time(Time.OutputMode.ABSOLUTE,2))
                            .commit().onComplete(new AsyncOperation.CompletionHandler<RouteManager>() {
                        @Override
                        public void success(RouteManager result) {
                            result.subscribe(X_DATA, new RouteManager.MessageHandler() {
                                @Override
                                public void process(Message message) {
                                    Log.i("X Axis", " " + message.getData(Float.class));
                                }
                            });
                        }
                    });

                    debugModule=mwBoard.getModule(Debug.class);

                } catch (UnsupportedModuleException e) {
                    Log.e(LOG_TAG,"Cannot find module",e);
                }


            }

        });
        mwBoard.connect();
    }

    @Override
    public void onServiceDisconnected(ComponentName name) {

    }
}

Eric · April 2016

1) The passthrough filter you are using, as presently configured, is blocking all incoming data.

2) You should be able to manipulate accelerometer data in that fashion (math ops, comp, etc.) using feedback loops. What specifically are you trying to compute?

3) Depends on how you want to use the data. You can use an ArrayList to temporarily store data, an SQLlite database for persistance, or use an CSV file / cloud solution for exporting data to other machines.

maryfertg · April 2016

Thanks Eric,

You are very helpfully. For my project I want to implement this code,where (x,y,z) are accelerometer data (x,y,z) and analice 50 data each time

suma=0;

muestras=50;

est_ant=1;

r=y-z;

vu=-0.1;

%%This process have to repeat all the time

while muestras~=0

if r<=vu

suma=suma-1;

else

suma=suma+1;

end

muestra=muestra-1;

end

if muestra==0

if suma==49||
suma==50

disp('message 1')

est_ant=1;

else

if
suma==-49|| suma==-50

disp ('message
2')

est_ant=-1;

else

if
est_ant==-1

disp('message
2')

else

if
est_ant==1

disp('message 1')

end

muestras=50;

suma=0;

After I want to reemplace the disp('message 1') for some
action like a sound, a message... In addition I need to save how many time appear the message 1 and message
2 result in a day or during a period of time the app was used. I can save this
information in a document to send or only show before close the app.

Eric · May 2016

I'm not sure if you can build a data processing chain that can accomplish the same thing as your code. The biggest roadblock is the accumulator variable (suma) that is either incremented or decremented based on some condition; there is direct equivalent of this in the data processor. Furthermore, there is no boolean logic in the data processor. In your case, an OR operation should be ok if you have 2 separate signals that trigger the same action.

I played around with the API a bit and came up with this way to compute "y-x" using solely the data processing.

final Accelerometer accModule= mwBoard.getModule(Accelerometer.class);
accModule.routeData().fromYAxis().process(new Sample((byte) 1)).process("y-axis", new Maths(Maths.Operation.SUBTRACT, 0)).stream("difference")
        .commit().onComplete(new CompletionHandler<RouteManager>() {
            @Override
            public void success(RouteManager result) {
                result.subscribe("difference", new RouteManager.MessageHandler() {
                    @Override
                    public void process(Message msg) {
                        Bmi160SingleAxisMessage bmi160Msg= (Bmi160SingleAxisMessage) msg;
                        short unscaled= (short) (bmi160Msg.getData()[0] | (bmi160Msg.getData()[1] << 8));
                        Log.i("test", "Difference= " + (unscaled / bmi160Msg.getScale()));
                    }
                });
            }
        });
accModule.routeData().fromXAxis().monitor(new ActivityHandler() {
    @Override
    public void onSignalActive(Map<String, DataProcessor> processors, DataToken token) {
        processors.get("y-axis").modifyConfiguration(new Maths(Maths.Operation.SUBTRACT, token));
    }
}).commit();

Accelerometer Data

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