MicroBleMobile Design Tips

MicroBleMobile is an adapter interface tool for transfer from micro:bit to Unity on Android mobile phone using BLE (Bluetooth low energy). By connecting the sensor device (gyro, accelerometer, GPS, etc.) with micro:bit you can input various sense data to Unity. You can also output various data from Unity by connecting the display device (LED, LCD panel, etc.) with micro:bit. This design tip explains how to modify for transfer data between Unity and micro:bit based on the purchased Unity script example and the purchased micro:bit code. MicroBleMobile transfers array data up to 64 bytes from Unity to micro:bit and array data up to 64 bytes from micro:bit to Unity by changing the Unity script example and the micro:bit code.

1. How to transfer data from micro:bit to Unity
1.1 How to set up data to Unity in micro:bit
1.2 How to get data from micro:bit in Unity
2. How to transfer data from Unity to micro:bit
2.1 How to set up data to micro:bit in Unity
2.2 How to get data from Unity in micro:bit

1. How to transfer data from micro:bit to Unity

1.1 How to set up data to Unity in micro:bit

The micro:bit code ‘microble-v2.1.ino’ generates 3D Object ‘tumbler’ tilt data ‘x, y, z’ using the “SIN” function and convert it to strings using the “sprintf” function. The micro:bit code needs to change the strings to byte array data type using ‘saccel.getBytes’ function for sending data to Unity when micro:bit connects some sensors device.

   …

void setAccelCharacteristicValue() {
  sprintf(param, "degx:%d degy:%d", degx[value], degy[value]);
  Serial.println(param);

  x = sin(degx[value] / (180 / PI));
  y = sin(degy[value] / (180 / PI));
  sprintf(formatted_msg, "%4.2f,%4.2f,%4.2f,", x, y, z);
  Serial.println(formatted_msg);

  String saccel = String(formatted_msg);
  //Serial.println(saccel);
  byte sbyte[saccel.length()];
  saccel.getBytes(sbyte, saccel.length() + 1);
  accelCharacteristic.setValue(sbyte, saccel.length());

   …
}
   …

The micro:bit code ‘microble-v2.1.ino’ calls the ‘setValue’ function in the following format for sending data to Unity.

  
void setValue(byte[] sbyte, int length);

1.2 How to get data from micro:bit in Unity

Unity script example ‘MicroBleMobileSampleCode.cs’ receives BLE data from micro:bit as byte array data ‘str’ of return value of ‘obj.Call(“UpdateRead”)’ function. The byte array data ‘str’ encodes string code using ‘System.Text.Encoding.UTF8.GetString’ function and, using ‘text.Split’ function and ‘float.Parse’ function, the string code is converted to float position data.

       ...
// Update is called once per frame
void Update()
{
    float[] acceldata = new float[3];
    //byte[] indata = new byte[64];
    //int length = 0;

    byte[] str = obj.Call<byte[]>("UpdateRead");
    UnityEngine.Debug.LogWarning(TAG + " Update: " + str.Length);

    if (str.Length == 0)
    {
        UnityEngine.Debug.LogWarning(TAG + " Not connect ");
        return;
    }

    try
    {
        string text = System.Text.Encoding.UTF8.GetString(str);
        UnityEngine.Debug.LogWarning(TAG + " indata: " + text);

        string[] arr = text.Split(',');
        acceldata[0] = float.Parse(arr[0]);
        acceldata[1] = float.Parse(arr[1]);
        acceldata[2] = float.Parse(arr[2]);
        UnityEngine.Debug.LogWarning(TAG + " x: " + acceldata[0] + " y: " + acceldata[1] + " z: " + acceldata[2]);

        accelx = acceldata[0] * 100 + (-90);
        accely = acceldata[1] * 100;
        accelz = acceldata[2] * 100;

        transform.rotation = Quaternion.AngleAxis(accelx, Vector3.up) * Quaternion.AngleAxis(accely, Vector3.right);
    }
    catch (Exception e)
    {
        UnityEngine.Debug.LogWarning(TAG + e.ToString());
    }
    finally
    { }
}
       ...

Unity script example ‘MicroBleMobileSampleCode.cs’ calls the ‘Call(“UpdateRead”)’ function in the following format for reading data from micro:bit.

byte[] Call("UpdateRead");

2. How to transfer data from Unity to micro:bit

2.1 How to set up data to micro:bit in Unity

Unity script example ‘MicroBleMobileSampleCode.cs’ call back ‘ButtonClick’ function at button ‘On’ clicked. ‘ButtonClick’ function inputs data from ’inputFieldno0’ / ‘inputFieldno1’, then calls ‘obj.Call(“Command”, writedata)’ function with the parameter of ‘writedata’ byte array.

   …
public void ButtonClick()
{
    UnityEngine.Debug.LogWarning(TAG + " ButtonClick "); ;

    byte[] writedata = new byte[2] { byte.Parse(inputFieldno0.text), byte.Parse(inputFieldno1.text) };

    bool result = obj.Call<bool>("Command", writedata);
    if (!result)
    {
        UnityEngine.Debug.LogWarning(TAG + " Not connect ");
        return;
    }

    UnityEngine.Debug.LogWarning(TAG + writedata[0] + " " + writedata[1]);
}

Unity script example ‘MicroBleMobileSampleCode.cs’ calls the ‘Call(“Command”)’ function in the following format for sending byte array data to micro:bit.

 
bool Call("Command", byte[] data);

2.2 How to get data from Unity in micro:bit

The micro:bit code ‘microble-v2.1.ino’calls back ‘getContolCharacteristicValue’ function at received data from Unity. The ‘getContolCharacteristicValue’ function receives Inputfield ’No0’ / Inputfield ‘No1’ of Unity as 2 bytes of data using the ‘controlCharacteristic.value’ function.

   …

void getContolCharacteristicValue() {
  Serial.println("************** receive data! ******************");
  if (controlCharacteristic.value()) {
    byte row = controlCharacteristic.value()[0];
    byte col = controlCharacteristic.value()[1];
    Serial.println(row);
    Serial.println(col);

    led_pset(col, row, HIGH);
    delay(200);
    led_pset(col, row, LOW);
  }
}
   …

The micro:bit code ‘microble-v2.1.ino’ calls the ‘value’ function for receiving byte array data in the following format from Unity.

byte value()[x];

x: byte array index
return: byte