Application to Debug Serial Port Communication

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Introduction

This is a very basic testing tool that I created to test my serial port handling code. I did Google for such a basic tool which you would think would exist, but...

A Few Things You Might Need

I bought a few cheap USB to serial port cables which are helpful for testing on one machine. You can also install emulated serial ports, but I'd rather go with a more real scenario for testing.

Basic Features

1. The application allows you to send / receive data over the serial port and save it.
2. It allows you to configure all options of the .NET SerialPort class with a propertyGrid.
3. It allows you to select a directory and randomly send a file from that directory at a random interval.
4. It enumerates the COM ports on your machine.

Using the Code

Almost all the functionality in the app is a one liner and completely self explanatory because .NET is such a well written high level language. The only tricky part of this app is that the serial port receives data on a separate thread. You cannot access visual controls from a separate thread, so you must invoke a delegate that will set the text and send a copy of the memory with (new object[] { text }).

It is important to notice that InvokeRequired will let you know if the thread ID is different.

What will happen when we receive data is, serialPort1_DataReceived handler will be fired when serial data is received and it will call SetText which is just a little wrapper that will in turn invoke the SetTextCallback delegate. The delegate is set to call SetText so SetText will be invoked again, but now it is on the UI thread. At this point, this.txtData.InvokeRequired will be false and we can set the text like we normally would.

// This delegate enables asynchronous calls for setting
// the text property on a TextBox control.
delegate void SetTextCallback(string text);
private void serialPort1_DataReceived
    (object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
{
    SetText(this.serialPort1.ReadExisting());
}

private void SetText(string text)
{
    // InvokeRequired required compares the thread ID of the
    // calling thread to the thread ID of the creating thread.
    // If these threads are different, it returns true.
    if (this.txtData.InvokeRequired)
    {
        SetTextCallback d = new SetTextCallback(SetText);     
        this.Invoke(d, new object[] { text });
    }
    else
    {
        this.txtData.Text = text;
    }
}

Limitations

The serial app I am testing deals with old data matrix printer drivers and so I'm dealing with strictly text data going through the port, which is probably not what most people are looking for. I realize it would be more generically useful if it had a binary editor built in.

History

• 14^th May, 2007: Initial post