Arduino + HC-05 + AndroidVR App (using Unity google cardboard)

Question

I have been trying this for a week now ...I just not getting what's going on. So here what I'm trying to achieve.

I want to send my MPU_6050 data to AndroidVR app via classic HC-05 Bluetooth module.so that I can rotate the cube.

First of all ,all by connection are good well connected and working coz I have used in Terminal App.

I have performed the same thing using Serial Port with Desktop it work like charm...I just need to print the data in series as

1.01,22.1,35.1,

using Serial.print();

and on unity side I can get the value in string Array and can split() function something like this

string[] output_array = sp.ReadLine().Split(',');

here is sp is serial class object . but I cant used Serial port in Android .Can I?

so I'm using this Bluetooth plugin : https://assetstore.unity.com/packages/tools/input-management/android-microcontrollers-bluetooth-16467

Now the problem I'm facing is first in Arduino ... as i'm using

Serial.write();

so I won't get the accurate result eg: 0.36 would be 0
second if the value is -14.3 i.e., negative so it would be 255-14 it wold send 241

Now in the Unity I don't know how do I split the data ... and get the value from the list . converting it to string in Unity would give ASCII value which I don't want.

Below is the simple code...please help me with this .

Arduino code :

#include <Wire.h>
#define SEPARATOR 255
void setup()
{      
  Serial.begin(115200);
  Wire.begin();

  calibrate_sensors();  
  set_last_read_angle_data(millis(), 0, 0, 0, 0, 0, 0);
}
 void loop()
{ 
  /* Every thing above work well and all calculation are Performed
  I'm using Complimentary Filter for MPU6050 */

  byte buf[]={angle_x ,angle_y, angle_z,SEPARATOR}; 
  //here first three values are x,y,z angle and a separator(255 as per ASCII) 

  Serial.write(buf,sizeof(buf));//sending the data(byte array) via HC-05. 
}

Unity C# code:

using UnityEngine;
using System.Collections;
using UnityEngine.UI;
using TechTweaking.Bluetooth;

public class JoystickHandler : MonoBehaviour
{
    private BluetoothDevice device;
    public Text statusText;
    public Text logsOnScreen;

    public Transform cube;


    public float speed = 1.0f;

    void Awake()
    {
        statusText.text = "Status : ...";

        BluetoothAdapter.enableBluetooth();
        device = new BluetoothDevice();
        device.Name = "HC-05";
        //device.MacAddress = "XX:XX:XX:XX:XX:XX";

        device.setEndByte(255);

        device.ReadingCoroutine = ManageConnection;


    }

    public void connect()
    {
        device.connect();
    }

    public void disconnect()
    {
        device.close();
    }

    IEnumerator ManageConnection(BluetoothDevice device)
    {
        statusText.text = "Status : Connected & Can read";
        while (device.IsConnected && device.IsReading)
        {
            byte[] packets = device.read();

            if (packets != null)
            {
                statusText.text = "so we got some data";
                int val1 = packets[0];
                int val2 = packets[1];
                int val3 = packets[2];

                logsOnScreen.text = val1+" , "+val2+","+val3;

                cube.Rotate(val1,val2,val3);
            }
            yield return null;
        }
        statusText.text = "Status : Done Reading";

    }
}

I know I know its not the prettiest code ...but just trying to achieve the goal and I know I should have used Vector3 and other but this is just for testing purpose ...so kept simple .Please let me know your thought.

score 0 · Answer 1 · answered Mar 15 '22 at 09:03

Way too late but the answer may be useful for strangers wandering by

The problem is that you're taking 3 floating point values and converting them into bytes to send them across the bluetooth serial stream. When you do this conversion you are getting signed 8-bit integers, which is why the decimal values are dropped and why negative values wrap around to high byte values (the sign bit in action).

There are 3 ways to fix this problem

Use Serial.print(...) to send the numbers as text, this is less efficient and forces you to do a parse at the other end, it is however pretty simple and works fine for small applications
Multiply the values by 100 to elminiate the decimal points, then divide them by the same value at the other end. In this case an 8-bit integer will not suffice so you will need to use 16-bit ints, which again involves some annoying conversions.
Take the 4 bytes making up your floating point numbers and send those across. On the Arduino end you can use something like C Function to Convert float to byte array On the c# you can very easily convert them back using BitConverter.

Arduino + HC-05 + AndroidVR App (using Unity google cardboard)

Arduino code :

Unity C# code:

1 Answers1