Question/ Answers and References:-

1. MultiWii is a software to control a RC multi copter: MultiWii is an open source software project aiming to provide the brain of a RC controlled multi rotor flying platform. It is compatible with several hardware boards and sensors.
   1. MultiWii: Historic Home Page
   2. MultiWii: Wiki
   3. MultiWii: Download MultiWii_2.4
   4. MultiWii, some circuits and Question Answers: Berkely blog on RCgroups.com
   
   
   
2. Using MultiWii with nRF24L01+
   YouTube Video: Data telemetry with MultiWii integrated nRF24L01
   also view (optional)
   YouTube Video: IMU telemetry via nRF24L01 ack payload (arduino) by the same author
   Code:
   • MultiWii_RF24.zip (Data telemetry with MultiWii integrated nRF24L01 )
   • Android app that shows telemetry stuff (Android Studio project, plz don't ask for help with this!)
   • Sketch for transmitter to go with above Android app. (Data telemetry with MultiWii integrated nRF24L01 )
   
   Cloud Rocket
   Adding nRF24L01based RX to MultiWii
   
   
3. Question: How to calibrate Accelerometer?
   Ans
   1. DisARM the copter. (The MultiWii GUI will show if it is armed). There would be some mechanism to DisARM it; It may be a Joystick combination OR Special button on remote to ARM/ DisARM the copter, this function acts as described in the MultiWii Arduino code.
      
   2. Calibrate the Accelerometer: YouTube 00:17:00 to end of video (1_7) CRIUS MultiWii SE V2.5 Board - Initial setup and configuration
   
   
4. Question: How to use AUX switches?
   Ans
   View the YouTube Video: Start Time: 00:04:00 to end of video
   (4_7) MultiWii modes - radio, connection and software setup
   
5. Question: How to orient MPU6050
   Ans: Example: What you think is X-axis in MultiWii GUI, is actually Y-axis on the GY-521 / MPU 6050. Here are some hints:
   1. From MPU6050 datasheet, refer this image. This image shows the manufacturer’s specifications of X, Y, Z axis w.r.t. MPU6050 silicon chip:
      
   2. Also check the physical orientation of MPU on the Quadcopter:
      
   3. Establish some relation between Quadcopter's (Roll, Pitch, Yaw) with X, Y, Z axis.
      Example: Something like:
      
   4. HINT: In the MultiWii code, find the lines like:
      
      and modify at the correct instance. These lines may be at multiple places in code, you need to figure out which onces will be complied for your quadcopter model.
   5. After above modifications, connect Quadcopter with MultiWii GUI and see real-time data again. You might need to repeat the process, while it is done correctly.
   
   
   
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