save into a txtfile realtime c++ - c++

Question

I have a problem, I have to save into a txt file a lot of data, the problem is that I receive them every 100ns from a serial port.
How can i do? I tried to put data on a RichTextBox but I receive a thread error.
Sorry for my English.
I'm using Windows 7 64bit
private: void FindPorts(void)
{
array<Object^>^ ListaPorte = SerialPort::GetPortNames();
this->cmbPort->Items->AddRange(ListaPorte);
}
private: System::Void btnOpenPort_Click(System::Object^ sender, System::EventArgs^ e)
{
if(this->cmbPort->Text==String::Empty || this->cmbBaudRate->Text==String::Empty)
this->rtbLog->Text="cmbError";
else
{
try{
if(!this->serialPort->IsOpen)
{
this->serialPort->PortName = this->cmbPort->Text;
this->serialPort->BaudRate = Int32::Parse(this->cmbBaudRate->Text);
this->serialPort->Open();
this->rtbLog->Text+="Porta aperta\r\n";
this->btnOpenPort->Text="Close Port";
}
else
{
this->serialPort->Close();
this->rtbLog->Text+="Porta chiusa\r\n";
this->btnOpenPort->Text="Open Port";
}
}
catch(UnauthorizedAccessException^)
{
this->rtbLog->Text+="UnauthorizedAccessException\r\n";
}
}
}
private: System::Void button1_Click(System::Object^ sender, System::EventArgs^ e)
{
if(!lettura)
{
lettura = true;
this->button1->Text="sto leggendo";
}
else
if(lettura)
{
lettura=false;
//rtbLog->Text += letturaBuffer;
this->button1->Text="sono ferma";
}
//serialPort->
}
private: System::Void serialPort_DataReceived(System::Object^ sender, System::IO::Ports::SerialDataReceivedEventArgs^ e)
{
if(lettura){
//letturaBuffer += serialPort->ReadExisting() + "\r\n";
rtbLog->Text += serialPort->ReadExisting() + "\r\n";
}
}

Answer 1

With a normal OS you wont be able to hold the pace if the data always comes at 100ns interval. 100ns interval is 10MHz so you should look for a realtime OS's that can deal with that speed. To display it in realtime you need lightweight components, so actually you should benchmark that RichTextBox and check if it can handle 10MHz.
Another problem you might have is the interrupt latency, if it takes 1us to get it, you already missed 10 data transfers.

Answer 2

It's unlikely you're getting data every 100 ns: The maximum speed for a standard serial port is 115,200 bits per second, which is 11,520 bytes per second, maximum. Even if your event is getting signaled for every byte received (also unlikely), that's every 87 microseconds, not every 100 nanoseconds.
The reason you're getting a thread error is because the serialPort_DataReceived method is being called on a threadpool thread, and UI components can only be accessed from the UI thread. Let's fix that, then worry about how often you want to do this, and whether it's possible in a non-RTOS.
It looks from your code like you're using WinForms, not WPF. Give this a try:
void AddAString(String^ s)
{
this->rtbLog->Text += (s + Environment::NewLine);
}
void serialPort_DataReceived(Object^ sender, SerialDataReceivedEventArgs^ e)
{
if(lettura)
{
this->BeginInvoke(
gcnew Action<String^>(this, MyClass::AddAString),
serialPort->ReadExisting());
}
}