Packing data of multiple sensors

Comments

• Laura

  February 2021 edited February 2021

  Sensor fusion is just a kalman filter. It will take the output of the acc, gyro, and mag and turn it into euler or quaternions.
  It doesn't sound like that's what you want thought. It looks like you want raw data.

  The issue is that Bluetooth isn't very fast so 100Hz acc + 100Hz gyro is outside the limits of BLE.

  We do have two things you should try out:

  1) We have a mode that allows you to pack 3 data points into 1 ble packet for one sensor (this would be for acc OR gyro, this doesn't combine them). It's called the packed mode.
  You could do a packed mode acc and a packed mode gyro and see if you get all your data that way.

  2) We have a fuser mode that allows you to put 1 acc data point and 1 gyro data point into a single ble packet.
• mehdieji

  February 2021

  Thanks for your response, Laura.
  Yes, I need raw data for further analysis is an activity recognition system.
  About the 1st option that you mentioned, I am already doing so. Meaning that I get the packed data of acc and the packed data of gyro. the problem is that the received packets are not necessarily gyro/acc on every other packet and I sometimes get 2 (or even 3) packets of packed acc consecutively. That makes things complicated when trying to rebuild a real-time set of acc and gyro data.
  About your second suggestion, that sounds exactly like what I'm looking for, Yet I have not been able to find anything yet... So how can I access this fuser mode that you mentioned? That seems like something different from sensor fusion of the API because there is no mode of sensor fusion alike our topic as far as I know.
  Thanks again for the great support.
• Laura

  February 2021

  Just look at the fuser in our dataprocessor tutorials
  Also sensor fusion might work better for you, it's how we made MetaRom.
• mehdieji

  February 2021

  I tried to implement fuser exactly as mentioned in the doc for SDK 3.7
  I defined a function as follows and I made sure to call it after I have configured and started sensors. But it seems that there is something wrong with the buffer method because I don't get any of the logs inside my onSuccessTask. I have configured both sensors at 100 Hz.

  // Inside onServiceConnected I have configured the modules accelerometer and gyroscope ...
  
  /* Inside onCreate I am enabling the modules. Also I am calling
   the fuseImuData function inside onCreate to make sure that modules
   are already active. After I press a start button, the following code runs */
  
  
  accelerometer.acceleration().start();
  gyroscope.angularVelocity().start();
  accelerometer.start();
  gyroscope.start();
  fuseImuData(accelerometer, gyroscope);
  
  
  public void fuseImuData(Accelerometer accelerometer, GyroBmi160 gyroscope){
          gyroscope.angularVelocity().addRouteAsync(source -> {
              source.buffer().name("gyro-buffer");
              Log.i(TAG,"Gyro buffered");
          }).onSuccessTask(ignored -> accelerometer.acceleration().addRouteAsync(source ->
              source.fuse("gyro-buffer").limit(10).stream((data, env) -> {
          Data[] values = data.value(Data[].class);
          // accelerometer is the source input, index 0
          // gyro name is first input, index 1
          Log.i(TAG,"Fusing completed");
          Log.i(TAG,"IMU Data: "+values[0].value(Acceleration.class).toString()+" "+
                  values[1].value(AngularVelocity.class).toString());
  })));}
  

  I don't get the "Fusing completed" Log so the buffering has not been successful. Can you please help me with this?