no connection to the serial port with windows

Getting Started
1

Hello,
I am new to Xojo and I wrote a small app that sends and receives data to/from an Arduino uno. I use the Portlistupdater as in the tutorial for the Barcodereader (code below).
The app works fine on my Mac in the debugger. Now I have tried the program on a Windows10 laptop in the Xojo debugger. According to system control, the Arduino is at COM port 3. But my SerialPortsPopupMenu shows COM4. Of course, a connection is impossible.
When I unplug the USB cable, it changes to COM5.
With the serial monitor of the Arduino-IDE I can easily send and receive data via COM3.
Does anyone know what’s wrong? I get more and more desperate if I can’t figure it out.

Code (PortListUpdater -> Run):

Dim count As Integer = SerialPortsPopupMenu.ListCount

If System.SerialPortCount <> count Then
// The number of serial devices has changed so update the menu
SerialPortsPopupMenu.DeleteAllRows
For i As Integer = 0 To System.SerialPortCount - 1
SerialPortsPopupMenu.AddRow(System.SerialPort(i).Name)
Next
If System.SerialPortCount < count Then // a device has been removed
SerialPortsPopupMenu.ListIndex = 0
Else // one has been added so select the new device
SerialPortsPopupMenu.ListIndex = System.SerialPortCount - 1
End If
End If

2

One recommendation it to make certain you .Close() the open serial port after you finish using it.

3

This is the code for the open/closed button event (also like in the tutorial):
If Me.Caption = “Disconnect” Then // Disconnect from the serial port
Serial1.Close
Me.Caption = “Connect”
SerialPortsPopupMenu.Enabled = True
PortListUpdater.Mode = Timer.ModeMultiple ’ turn it on
Else // Connect to the serial port
// Set the serial port to the index of the one chosen in the popup menu
Serial1.SerialPort = System.SerialPort(SerialPortsPopupMenu.ListIndex)
If Serial1.Open Then
Me.Caption = “Disconnect”
SerialPortsPopupMenu.Enabled = False
PortListUpdater.Mode = Timer.ModeOff
Else
Beep
MessageBox(“The selected serial port could not be opened.”)
End If
End If

But I can not connect to the port at all. It is not found if the app is startet with windows.

4

Windows, Linux, Mac all have their subtle differences in how their serial ports behave - but don’t worry, there are solutions.

You may want to code your serial interface to more dynamic, and less “hard coded”. Don’t rely on Windows to ever hand you a proper port# consistently.

Here’s what I do…

1.- Monitor the serial ports constantly and look for changes in the # of ports (just like the example code demonstrated).
2.- Create a list of objects that hold all the serial pointers.
3.- Iterate thru each of them, looking for ports that will open (not in use).
4.- Open each idle port, using the serial config appropriate for your Arduino (correct Baud rate, etc.).
5.- Interrogate the port by using a serial command that the Arduino will respond to, assuring you’ve landed on the right port.
6.- Use the port you allocated in step #5.

This method is a bit exotic, but it works across most every platform, and allows for some elegant “auto connect” plug-and-play behavior.

5

Thank you very much for your help. I think you gave me an idea.

When I do the following:
For i As Integer = 0 To System.SerialPortCount - 1
MsgBox(System.SerialPort(i).Name)
Next

… comes COM5 first, then COM3 and then after a break COM4. Com4 is always listed last.

But when one device is added (in my case COM3), the code from the tutorial sets:
SerialPortsPopupMenu.ListIndex = System.SerialPortCount - 1

and so I always try to connect to Port COM4.

Tomorrow I’ll report whether I succeed to solve the problem.