Display text from serial port in TextBOX

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Dear all,

Happy new year!

I am currently working on programming a small serial port software in VC2008.

The aim of this software is to receive the GPS data from serial port and display the data (or text) in the TextBox in windows form interface. I had setting up the serial port and all is right. the problem is when I started to receive the data text, it can only display one line in TextBox.I pasted my key part of code here,

C++

port->Open();
 
// read a line of data from serial port
 
StreamWriter^ sw = gcnew StreamWriter("GPSdata.txt");
 
String^ txt = port->ReadLine();
 
TextBox1->Text = txt;
 
while (( txt = port->ReadLine())!= nullptr)
 
{
 
//sw->WriteLine(txt);
 
TextBox1->Text = txt;
 
sw->Flush();
 
}

I found that if I changed the StreamWriter to write the txt into a file but no need to display in TextBox, the program is right and data can be input in file, but if i need the the data saving in file and displaying on TextBox at the same time, it will break down...

Any helps could be very appreciated.

Many thanks.

Posted 8-Feb-11 2:12am

HAOYE850815

Updated 8-Feb-11 2:13am

Prerak Patel

v2

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Andrew Brock · Accepted Answer · 2011-02-08T02:45:00

Solution 1

You need to append to the text box, not change the text.

port->Open();
// read a line of data from serial port
StreamWriter^ sw = gcnew StreamWriter("GPSdata.txt");
String^ txt = port->ReadLine();
TextBox1->Text = txt;
while (( txt = port->ReadLine())!= nullptr) {
	//sw->WriteLine(txt);
	TextBox1->Text += txt;
	//You may also need a + "\r\n" if txt doesn't have a new line sequence
	//TextBox1->Text += txt + "\r\n";
	sw->Flush();
}

Also make sure the text box is multiline.

Posted 8-Feb-11 2:45am

Andrew Brock

Comments

Nish Nishant 8-Feb-11 9:11am

Voted 5, proposed as answer.

HAOYE850815 8-Feb-11 9:30am

Hello Andrew, thanks for your reply. I changed the code as what you said. But the situation is the program is stopped without any reaction. I am not sure, it still no data on the textBox?
// open the serial port
port->Open();
// create a file to write
String^ txt = port->ReadLine(); StreamWriter^ sw = gcnew StreamWriter("GPSdata.txt");
//TextBox1->Text += txt + "\r\n";
while (( txt = port->ReadLine())!= nullptr)
{
//String^ txt = port->ReadLine();
//sw->WriteLine(txt);
TextBox1->Text += txt + "\r\n";
sw->WriteLine(txt);
sw->Flush();
}
//sw->Close();

Andrew Brock 8-Feb-11 9:37am

Some things to look for:
1. Make sure code flow is making it over the line "String^ txt = port->ReadLine();"
2. Make sure the text is getting read correctly from the port.

You can find both of these by inserting a breakpoint on the lines "String^ txt = port->ReadLine();" and "TextBox1->Text = txt;" to make sure the code is getting executed, and that port->ReadLine() is not blocking execution waiting for data.