Exception thrown when connecting to MetaMotionR device

Comments

• Eric

  September 2019

  https://mbientlab.com/community/discussion/3167/how-to-report-an-issue#latest
• FloNas

  September 2019

  @Eric said:
  https://mbientlab.com/community/discussion/3167/how-to-report-an-issue#latest

  Hello,

  I'm sorry for my negligence.

  1. Board Information:
     Hardware revision: 0.4
     Firmware revision: 1.4.4
     Model number: 5

  2. Host Device Information: Laptop with Windows 10 x64, version 1809.

  3. SDK: I am using Visual Studio 2017, version 15.9.14

  Thank you,
  Florin
• Eric

  September 2019

  I don't see anything obviously wrong in your code snippets.

  The stack trace points to this function but I also don't see how it would be throwing an InvalidOperationException.

  Please provide a self contained piece of metawear SDK calls that replicates the issue We should able to copy/paste the code and run it ourselves with minimal effort.
• FloNas

  September 2019

  The code to reproduce the problem is the following. What you need is to add objects of type "BluetoothLEDevice" into the list "DeviceList" or to replace the list with a single element. I used the code from the BtleDeviceScanner project from the MetaWear tutorials to create BluetoothLEDevice objects.

  What you need to do to recreate the problem is to call the "Connect" method several times consecutively. I found that this exception does not occur in a regular manner.

  using MbientLab.MetaWear;
  using MbientLab.MetaWear.Core;
  using MbientLab.MetaWear.Data;
  using MbientLab.MetaWear.Sensor;
  using MbientLab.MetaWear.Win10;
  using System;
  using System.Collections.Generic;
  using System.Threading;
  using System.Threading.Tasks;
  using Windows.Devices.Bluetooth;
  
  private List<BluetoothLEDevice> DeviceList = new List<BluetoothLEDevice>();               
  public List<double> GetX { get; } = new List<double>();
  public List<double> GetY { get; } = new List<double>();
  public List<double> GetZ { get; } = new List<double>();
  IMetaWearBoard _metawearDevice = null;
  
  // MAC of the desired BLE device, format "xx:xx:xx:xx:xx:xx"
  public void Connect(string MAC, int retries = 1)
  {
      if (_metawearDevice != null)
      {
          StopAndDisconnectMotionSensor();
      }
      ConnectToSensor(MAC.Trim(), retries);
  }
  
  public void StopAndDisconnectMotionSensor()
  {
      StopAccelerometer(_metawearDevice);
      Task task = Task.Run(async () => await Disconnect(_metawearDevice));
  }
  
  public void StopAccelerometer(IMetaWearBoard _metawearDevice)
  {
      if (_metawearDevice == null)
      {
          throw new ArgumentNullException("The provided device is null!");
      }
  
      var acc = _metawearDevice.GetModule<IAccelerometer>();
      // Put accelerometer back into standby mode
      acc.Stop();
      // Stop accelerationi data
      acc.Acceleration.Stop();
  }
  
  public async virtual Task Disconnect(IMetaWearBoard _metawearDevice)
  {
      if (_metawearDevice == null)
      {
          throw new ArgumentNullException("The MetaWear device instance is null!");
      }
  
      _metawearDevice.TearDown();
      // Have the board terminate the BLE connection
      await _metawearDevice.GetModule<IDebug>().DisconnectAsync();
  }
  
  public void ConnectToSensor(string MAC, int retries = 3)
  {
      BluetoothLEDevice device = DeviceList.Find(x => ConvertToMAC(x.BluetoothAddress).Trim() == MAC.Trim());
      Task task = Task.Run(async () => await AttemptConnect(device, retries));
  }
  
  private async Task AttemptConnect(BluetoothLEDevice BLEDevice, int retries)
  {
      _metawearDevice = await ConnectToDevice(BLEDevice, retries);
  
      if (_metawearDevice != null)
      {
          Task task = Task.Run(async () => await Setup(_metawearDevice));
          SetAccSamplingRate(_metawearDevice, 100f, 16f);
          StartAcc(_metawearDevice);
      }
  }
  
  public async Task Setup(IMetaWearBoard device, float connInterval = 7.5f)
  {
      if (device == null)
      {
          throw new ArgumentNullException("The provided device is null!");
      }
  
      // Set the connection interval
      await SetBLEConnectionInterval(device, connInterval);
      var acc = device.GetModule<IAccelerometer>();
  
      // Use data route framework to tell the MetaMotion to stream accelerometer data to the host device
      await acc.Acceleration.AddRouteAsync(source => source.Stream(data =>
      {
          // Clear buffers if there is too much data inside them
          if (GetX.Count > 1000)
          {
              ClearSensorData();
          }
  
          // Buffer received data
          GetX.Add(data.Value<Acceleration>().X);
          GetY.Add(data.Value<Acceleration>().Y);
          GetZ.Add(data.Value<Acceleration>().Z);
      }));
  }
  
  public void ClearSensorData()
  {
      GetX.Clear();
      GetY.Clear();
      GetZ.Clear();
  }
  
  private async Task SetBLEConnectionInterval(IMetaWearBoard device, float maxConnInterval = 7.5f)
  {
      if (device == null)
      {
          throw new ArgumentNullException("The provided device is null!");
      }
  
      // Adjust the max connection interval
      device.GetModule<ISettings>()?.EditBleConnParams(maxConnInterval: maxConnInterval);
      await Task.Delay(1500);
  }
  
  public void SetAccSamplingRate(IMetaWearBoard device, float samplingRate = 100f, float dataRange = 16f)
  {
      if (device == null)
      {
          throw new ArgumentNullException("The provided device is null!");
      }
  
      var acc = device.GetModule<IAccelerometer>();
      // Set the data rate and data to the specified values or closest valid values
      acc.Configure(odr: samplingRate, range: dataRange);
  }
  
  public void StartAcc(IMetaWearBoard device)
  {
      if (device == null)
      {
          throw new ArgumentNullException("The provided device is null!");
      }
  
      var acc = device.GetModule<MbientLab.MetaWear.Sensor.IAccelerometer>();
      // Start the acceleration data
      acc.Acceleration.Start();
      // Put accelerometer in active mode
      acc.Start();
  }
  
  public async virtual Task<IMetaWearBoard> ConnectToDevice(BluetoothLEDevice device, int retries = 1)
  {
      _metawearDevice = Application.GetMetaWearBoard(device);
  
      if (_metawearDevice == null)
      {
          throw new ArgumentNullException("The MetaWear device is null!");
      }
  
      // How long the API should wait (in milliseconds) before a required response is received
      _metawearDevice.TimeForResponse = 5000;
      int x = retries;
  
      do
      {
          try
          {
              await _metawearDevice.InitializeAsync();
              retries = -1;
          }
          catch (Exception e)
          {
              retries--;
          }
      } while (retries > 0);
  
      if (retries == 0)
      {
          return null;
      }
      else
      {
          return _metawearDevice;
      }
  }
  

  Thank you,
  Florin
• Eric

  September 2019

  Well, there's your problem, you need to wait for async tasks to complete.
• FloNas

  September 2019

  @Eric said:
  Well, there's your problem, you need to wait for async tasks to complete.

  Can you please tell me where in the code above do I need to wait for async tasks to complete?

  Thank you,
  Florin