Serial communication in second thread, asynchronously?

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C#

C#4.0

Hi,

I want to put the serial communication with an external device to a second thread, c#.

Here there is my first thread doing some stuff.
And there is the serial worker, the second thread:
- It opens the serial port
- It asks the external serial device regulary: Are you alive?
- It receives queries from the first thread with a string and an int like: "Command2", 33 and it should give this to the
external serial device.
- Sometimes there comes an answer from the external serial device back with a string and an int like: "Command4", 55 and the second thread should give this to the first thread and it should start a process there.
- The second thread also does own things like error detection which I want to keep free the first thread of.

Serial communication itself works fine but I have problems with threads, delegates, BeginInvokes, EventHandlers, etc.

My first thread:

Class MainProgramme
{
internal void StartSerialCommunication
{
  //Here I want the second thread to open the serial port and I want to start the regulary serial device check, all in the second thread.
}
internal bool SerialCommand(string s, int i)
{
  //Here I want to give the command s and i to the second thread asynchronously. That means this process does not wait for an answer from the second thread.
}
//The following process should be fired by the second thread because the second thread has received some important data from the external serial device.
internal void SerialAnswered
{
  //Here I want to get the string and the int from the second device back.
}
}

My second thread:

Class SerialCommunication
{
internal bool SerialDeviceIsAlive = true;
public bool SerialOpen
{	
SerialPortMsp.Open();
RegularyDeviceCheckTimer.Enabled = true;
return true;
}
private void RegularyDeviceCheckTimer_Tick(System.Object 
sender, System.EventArgs e)
{
if SerialDeviceIsAlive == true)
{ 
SerialDeviceIsAlive == false;
}
else
{
  //Here I want to inform the first thread that the answer from the external serial device is missing.
}
SerialSend("AreYouAlive");
}
public void SerialReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
{ 
IAmAlive = true;
int buff = SerialPortMsp.ReadExisting();
if (buff.IndexOf(new string('\n', 1)) > 0)
{
  //Here I want to inform the first thread that the answer was buff.
}
}
public bool SerialSend(string SerialCommand) 
{
SerialPortMsp.Write(SerialCommand.ToCharArray(), 0, 
SerialCommand.Length);
return true;	
}
}

I need help in calling processes and transferring data between the two threads.
Thank you,