One of the requirements of my projects is to send data from my application to the Arduino robot.

I have windows 10, and my robot is Arduino Uno. The Bluetooth I'm using on my robot is HC-06.

The app side:

• I'm writing some script (With the format I've created)
• Then converting it into JsonString
• Opening the port and sending a start communication signal.
• Sending the JsonString, each represents another command and they're separated with a special character that can't be written in the script. Here's the problem, I tried sending string length of 256 bytes (not a JsonString) just to test the Bluetooth.

The test I did in my robot

• I read the data
• Turned the led on
• Waited (data.length() / 10) seconds
• Turned the led off

For my data of 256 bytes, the led was ON for 12.8 seconds, which is 128 bytes. And sometimes when I changed some stuff The time was 6.4 seconds.

C# (Application)

string data = @"0101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101";

protocolBT.BTcontroller.OpenPort();                   
protocolBT.BTcontroller.SendChar(ProtocolBT.COM_OpenChar);
protocolBT.BTcontroller.SendBigData(data);
protocolBT.BTcontroller.ClosePort();

The Bluetooth Class

public class BluetoothController
{
    private readonly SerialPort _serialPort;

    
    public BluetoothController(string portName, BaudRate baudRate)
    {
        _serialPort = new SerialPort(portName, (int)baudRate, Parity.None, 8, StopBits.One);
    }

    public static bool IsBluetoothSupported()
    {
        return BluetoothRadio.IsSupported;
    }

    public static void SetConnection()
    {
        if (IsBluetoothSupported())
        {
            if (BluetoothRadio.PrimaryRadio.Mode == RadioMode.PowerOff)
                BluetoothRadio.PrimaryRadio.Mode = RadioMode.Connectable;
        }
    }


    public void OpenPort()
    {
        try
        {
            _serialPort.Open();
        }
        catch(IOException IOex)
        {
            throw IOex;
        }
    }

    public void ClosePort()
    {
        _serialPort.Close();
    }

    public void SendData(string msg)
    {
        try
        {
            if (_serialPort.IsOpen)
            {
                byte[] data = Encoding.UTF8.GetBytes(msg);
                _serialPort.Write(data, 0, data.Length);
            }
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }


    public void SendBigData(string msg)
    {
        try
        {
            if (_serialPort.IsOpen)
            {
                foreach (char ch in msg)
                {
                    SendChar(ch);
                }
            }
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }

    public void SendChar(char ch)
    {
        try
        {
            if (_serialPort.IsOpen)
            {
                byte[] data = Encoding.UTF8.GetBytes(new char[]{ ch });
                _serialPort.Write(data, 0, data.Length);
            }
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }

}

And this is my Arduino test code

#include <SoftwareSerial.h>

#define RX 10
#define TX 11
SoftwareSerial BT = SoftwareSerial(RX, TX);


String startCom = "»";

String MessageStart = "";
bool isListen = false;
String data = "";

int yellow = 12;



void setup() 
{
  // Define LED
  pinMode(yellow, OUTPUT);

  // Test yellow led
  digitalWrite(yellow, HIGH);
  delay(1000);
  digitalWrite(yellow, LOW);
  
  // Define Bluetooth
  pinMode(RX, INPUT);
  pinMode(TX, OUTPUT);
  BT.begin(9600);
}


void loop() 
{
  if(isListen == false)
  {
    readStartCommand();
  }
  else if(isListen == true)
  {
    readAllData();
    
    int len = data.length();
    if(len > 0)
    {
      robotLedOn(0); // Turn on the yellow led
      for(int i = 0; i < len; i++) // Wait (len * 0.1) second
      {
        delay(100);
      }
      robotLedOff(0); // Turn off the yelloe led
    }
  }
}


void readStartCommand()
{
  if(BT.available() > 0)
  {
    char ch = BT.read();
    Message += ch;

    if(MessageStart == startCom)
    {
      // Blink the yellow led if the start communication command recieved
      robotLedOn(0);
      delay(1000);
      robotLedOff(0);
      delay(2000);

      MessageStart = "";
      isListen = true;
    }
  }
}

void readAllData()
{

  while(BT.available() > 0)
  {
    data += BT.read();
  }
  isListen = false;
}

I tried to put the 256 bytes data manually to string in the Arduino and the timer was on 25.6 seconds. So I think that there is a limit for the size of the data that Bluetooth can handle.