a noob want to use kitkat to build a project. (helping..!!!)

Mark_L · July 2015

Hi everyone,

I am doing a simple project with metawear, just want to get the data from accelerometer and do some calculation. So the procedure should be started from:

1: ask user to allow to open the Bluetooth of their smartphone,

2: scan the available devices surrounding.(I want it scanning automatically after allowed and list all devices in a "small window")

3: feedback to user "connected" after tapping the correct one.

4: start to read the data from accelerometer of metawear.

5: convert to be a real acceleration.

7: do some calculation.

Is it correct?

It is my first time to use android studio and I don't have any experience with Java or other computer language. I will appreciate if you can teach me how to write the android code to access it step by step, I am just a newbie so I may need more your patience.

Thanks you so much and have a good day

Eric · July 2015

Yes, your steps outlined are correct.

I'd first start with a Hello World app. In other words, start a new project in Android Studio, walk through the wizard to get simple app running on your phone. Once you feel confident, please read our Android Getting Started guide (http://docs.mbientlab.com/?page_id=40) to get up to speed on the MetaWear library. The section on the Accelerometer module (http://docs.mbientlab.com/?page_id=40#post-95) explain how to interact with the accelerometer.

After that, check out some of our code, specifically the Accelerometer panel from the sample app and the SOSTrigger project for full code samples to study.

Mark_L · July 2015

Hi Eric,

Thank you for your reply. So now I need to finish the Bluetooth part(open scan and connectd) for my project. and what I have known so far just is

1. Layout is for user interface(so coding is for display or show to user)

2. java.MainActivity is for implementation, do some calculations like how the app run and what the function is.

and my plan is inside the MainActivity, I want to create an infinite while loop for data collecting and calculating and showing the result in real time to my phone.

So now what confusing me is that do I need to create another new activity for BLEservice only? or just mix up inside the MainActivity? because I saw their app has something called BLEServiceFragment.

and if yes, how can I connect these two activities?

Forgive my stupid question.

and there are some coding I have done so far, and can you help me to check? thanks again:)

//Enable the Bluetooth

public class MainActivity extends Activity implements ServiceConnection{

    private BluetoothAdapter mBluetoothAdapter;
    private static final int REQUEST_ENABLE_BT= 1;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

// Initializes Bluetooth adapter.
        final BluetoothManager bluetoothManager =
                (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
        mBluetoothAdapter = bluetoothManager.getAdapter();

        if (!bluetoothManager.getAdapter().isEnabled()) {
            final Intent enableIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
            startActivityForResult(enableIntent, REQUEST_ENABLE_BT);
        }
        //bind with metawear
        getApplicationContext().bindService(new Intent(this,MetaWearBleService.class),
                this, Context.BIND_AUTO_CREATE);
    }

Eric · July 2015

The MetaWear library has a background service that manages the Bluetooth LE connection, you do not need to create your own service for that task. Your code looks good so what I would do next is add the MetaWear broadcast receiver to your activity and setup the Bluetooth LE scanner (or hardcode your board's MAC address) to get your app to find your board.

Mark_L · July 2015

Hi Eric

Thank you so much!

I have completed the code which is for board connecting so far, meaning I can access the board now, using your SOS trigger project as reference

and now my facing problem is

I can not display the data from accelerometer on my phone as

public static class PlaceholderFragment extends Fragment implements ServiceConnection can't use the findViewByid function.

TextView activeCaloriesBurned = (TextView) findViewById(R.id.Condition);
activeCaloriesBurned.setText("" + X);

and where and how can I create a loop for calculating? thanks

public void setBtDevice(BluetoothDevice device) {

    mwController= mwService.getMetaWearController(device);
    mwController.setRetainState(false);
    mwController.addDeviceCallback(new MetaWearController.DeviceCallbacks() {
        @Override
        public void connected() {

            accelCtrllr= ((Accelerometer) mwController.getModuleController(Module.ACCELEROMETER));
            accelCtrllr.enableXYZSampling().withFullScaleRange(Accelerometer.SamplingConfig.FullScaleRange.FSR_2G)
                    .withOutputDataRate(Accelerometer.SamplingConfig.OutputDataRate.ODR_200_HZ);


            Toast.makeText(getActivity(), R.string.toast_connected, Toast.LENGTH_SHORT).show();
        }

        @Override
        public void disconnected() {
            Toast.makeText(getActivity(), R.string.toast_disconnected, Toast.LENGTH_SHORT).show();
        }
    }).addModuleCallback(new Accelerometer.Callbacks() {
        @Override
        public void receivedDataValue(short x, short y, short z) {
            Log.i("MainActivity", String.format(Locale.US, "(%.3f, %.3f, %.3f)",
                    x / 1000.0, y / 1000.0, z / 1000.0));
            accelCtrllr.startComponents();
        }

    });

    mwController.connect();
}

Mark_L · July 2015

Sorry, may my questions are not so clear.

what I am trying to say is

public void receivedDataValue(short x, short y, short z) {
            Log.i("MainActivity", String.format(Locale.US, "(%.3f, %.3f, %.3f)",
                    x / 1000.0, y / 1000.0, z / 1000.0));
            accelCtrllr.startComponents();
        }

this code is for data acquisition right? meaning the acceleration value is stored in the x, y, z, and I want to use them for calculating, so how can I achieve it? do I need to create a new class for it?

thanks again!

Mark_L · July 2015

and that is my whole code:

https://www.facebook.com/sharer/sharer.php?u=https://www.facebook.com/permalink.php?story_fbid=102550746759794&id=100010146061920&display=popup&ref=plugin (Can be seen?)

Thanks for your patience!

Eric · July 2015

The call to startComponents must be done in the connected callback function, after you've configured the acclerometer sampling. You have the startComponents call inside the receivedDataValue callback function.

Also, 200Hz is too high for streaming, you should lower it to 100Hz or 50Hz.

There are no loops needed to do your computation. The code inside receivedDataValue will be executed every time acclerometer sensor data has been received.

Mark_L · July 2015

Hi Eric:

What your meaning is I can do my calculation after the

            Log.i("MainActivity", String.format(Locale.US, "(%.3f, %.3f, %.3f)",
                    x / 1000.0, y / 1000.0, z / 1000.0));
            //start my calculation here?

inside the receivedDataValue function?

and what code can I use for display on the smartphone? because when I use

TextView activeCaloriesBurned = (TextView) findViewById(R.id.Condition);
activeCaloriesBurned.setText("" + X);

there is nothing to show even I assign a value short X=1;

thanks Eric

Eric · July 2015

Yes, you will do your calculation where your comment is.

Before we get to that though, is the receivedDataValue callback function being called at all? It doesn't seem like it is, otherwise you should be getting messages in Logcat. What does your code look like now? Also, I suggest posting your code in Pastebin (http://pastebin.com/) instead of a Facebook text wall.

Mark_L · July 2015

Hi Eric,

thanks, you help me a lot, and I have posted my code here http://pastebin.com/NEaDbfz3

could you just give me some direction?

next thing I need to do should calculating and display the result. but I don't know how to move on as it alway said the non-static can not be referenced from a static context.

thank you

Eric · July 2015

What line is this error occurring on?

Mark_L · July 2015

Hi Eric,

Can you access to the link? http://pastebin.com/NEaDbfz3 the is error is at line 187.

Eric · July 2015

Yes I can access the link. However, I don't see any issue with the code at line 187. What is the full error message? Also, if you comment out the TextView code, do log messages get printed to Logcat?

Mark_L · July 2015

Hi Eric,

the full error message said Non-static method 'findViewById(int)' cannot be referenced from a static context.

Eric · July 2015

Change "activeCaloriesBurned" to be a member variable of the PlaceholderFragment class
Assign it in onViewCreated
Remove the assignment on line 187

public class PlaceholderFragment {

private TextView activeCaloriesBurned;

@Override

public void onViewCreated(View view, Bundle savedInstanceState) {

activeCaloriesBurned= (TextView) view.findViewById(R.id.Condition);

super.onViewCreated(view, savedInstanceState);

}

Mark_L · July 2015

Thanks Eric, I can get the data and display it now.

next what I need to do is when the GPIO pin read the the signal as high, the timer and accelerometer will be start until become low for stopping. and display the how long the time it use and acceleration during the time.

can you guild me how to achieve it, thank you!!

Eric · July 2015

First, you should try to setup notifications for pin state changes using setPinChangeType and enablePinChangeNotification. This feature will let you receive notifications for when the input voltage changes.

Mark_L · July 2015

Hi Eric,

I have finished this part for notification. and now I have a question that :

how can I store all the accelerometer value inside a variable array like acc[] using a while loop when it is working? so that I can use it in another place.

I think should be inside the callback function.

addModuleCallback(new Accelerometer.Callbacks() {
    @Override
    public void receivedDataValue(short x, short y, short z) {
	//Here create a while loop for storing till it stop

    }

thanks

Mark

Mark_L · August 2015

double accX[],accY[],accZ[];
int i=0;

.addModuleCallback(new Accelerometer.Callbacks() {
    @Override
    public void receivedDataValue(short x, short y, short z) {
        
        do {
            accX[i] = x/1000.00;
            accY[i] = y/1000.00;
            accZ[i] = z/1000.00;

            i = i + 1;
        } while(//Condition start-logging and stop-exit);
    }

That is what I am trying to do it, but seem can't work, how can I fix it? and how to write the condition for logging when the accl start and exit when it stop. thank you.

Eric · August 2015

You should use a List to store the data, not an array. Arrays should only be used when you know what the array size will be. On the other hand, the List class is for storing an indeterminate amount of data.

Also, you do not need a while loop in the function. The only thing the function should do is add data to your list.

Mark_L · August 2015

Hi Eric,

Can I get more detail, as I never learn about it and don't know where to start, is it called the arraylist or linkedlist?

List listA = new ArrayList(); //like this?

and how about this tutorial?: http://tutorials.jenkov.com/java-collections/list.html something like this?

and do you have other some relative tutorials about the List function which may help me t understand? Thank you so much.

Eric · August 2015

Yes, that tutorial covers all the functionality you need for your task and I would use an ArrayList as the List of choice.

The Java website also provides good information about Lists.

https://docs.oracle.com/javase/tutorial/collections/interfaces/list.html

Mark_L · August 2015

Hi Eric,

My app will be exited automatically.

List AcceleLength;

.addModuleCallback(new Accelerometer.Callbacks() {
    @Override
    public void receivedDataValue(short x, short y, short z) {AcceleLength.add(z);// add data}

.addModuleCallback(new GPIO.Callbacks() {
    @Override
    public void pinChangeDetected ( byte pin, byte state) {
        if (state == 0) {
            accelCtrllr.startComponents();
        } else {
            accelCtrllr.stopComponents();

Iterator iterator = AcceleLength.iterator();//get data
while(iterator.hasNext()){
    length = (double) iterator.next();
    resultLength=resultLength+length;
}
lengthshow.setText(new DecimalFormat("##.##").format(resultLength));
AcceleLength.clear();}

there are no any problem indicating, just don't know why it will stop suddenly when I start the accelerometer.

Mark_L · August 2015

oh, I know why, because I forget the AcceleLength=new arrayList; thanks,

and now I am doing the last one which is multiple connection(connect two mtwear)

how can I do it? I know there is an sample app, but which part I should focus on? thanks

Laura · August 2015

Marc,

Check our Eric's post: http://projects.mbientlab.com/using-multiple-connected-metawears-with-android-api-v1-3/

a noob want to use kitkat to build a project. (helping..!!!)

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