Streaming accelerometer values from multiple MetaMotionR sensors with C++ API

vishwanathkr

Hello,

I extended the existing Sample UWP App - Freefall detector to stream acc values onto the console from two MetaMotionR sensors. I manage to get it working once in a while but briefly, after which it throws one of the following exceptions inconsistently.

//System.Runtime.InteropServices.SEHException

mbl_mw_acc_set_odr();

//System.AccessViolationException

mbl_mw_connection_notify_char_changed()

My pipeline is something like this:

        public DetectorSetup()

            this.InitializeComponent();

            btleconn = new List<BtleConnection>();

            for (id=0:numDevices)

                // Create two BtleConnection structs 

// Assign read, write characteristics to both.

            initDelegate = new Fn_IntPtr_Int(initialized);

        private void initialized(IntPtr board, int status)

            // Set Response time as 500 ms and ODR: 25 Hz. Write config.

            // Define dataHandlerDelegates for Acc

            // Subscribe to delegates

        private async void writecharacteristic(...)

            // Unchanged...

        private async void readCharacteristic(...)

            // Unchanged...

        protected async override void OnNavigatedTo(NavigationEventArgs e)

            // Get selectedDevices as a list. Tested and works!

            for (id=0:numDevices)

                selectedDevice = selectedDevices[id];

                // Code to register value changed notification on each device

                var tempBTLEConn = btleconn[id];

                board = mbl_mw_metawearboard_create(ref tempBTLEConn);

                boards.Add(board);

                mbl_mw_metawearboard_initialize(board, initDelegate);

        private void start_Click(object sender, RoutedEventArgs e)

            for (id=0:numDevices)

                    // Code to start Streaming acc

        private void stop_Click(object sender, RoutedEventArgs e)

            for (id=0:numDevices)

                // Code to stop Streaming acc

I intend to stream acc & gyr simultaneously over 2 MetaMotionR sensors. Any advice would be appreciated.

Eric

Please post the full code.  Also, can your Windows device stream from 2 boards using the MetaBase app?

https://www.microsoft.com/en-us/store/p/metabase/9nblggh4txj3

vishwanathkr

EDIT:

I am able to stream both sensors through the Metabase App I meant, which is very snappy.

My issues still unresolved. Find my code here:

Detector Setup: https://codeshare.io/21qmOX

MainPage: https://codeshare.io/5RB31V

Eric

The FreeFall app wasn't designed to work with multiple metawears.  The read and write characteristic functions are hardcoded to only interact with one device for one so it's unlikely your second device was ever initialized.  You should base your app off of the UWP template project instead of the ree fall tutorial

https://github.com/mbientlab/MetaWear-UwpStarter

vishwanathkr

Thanks Eric. It works like a charm now.