Serialport question

[Eric]

Hi,

I'm trying to read data from a device connected by SerialPort van MS CF2.0

I connect to the device and the send an INIT command to it.
The device then responds with some data.

Each time the datarecieved event is handled, I get the following
(translated) error:

NotSupportedException
No error message can be shown because an optional source-assembly can not be
found at
Miscrosoft.AGL.Common.MISC.HandleAR() at
System.Windows.Forms.Control.get_Text() at
MyProgram.Form1.prt_DataRecieved() at
System.IO.Ports.SerialPort.CatchRecievedEvents() at
EventLoopRunner.CallRecieveEvents() at
WorkItem.doWork() at
System.Threading.Timer.ring()


Can anyone tell me what this means, please, and how can I solve this?

rg.
Eric

 

[Daniel Moth]

Are you trying to touch controls directly from the event handler of the data
received?

If so, you should use Control.Invoke:
http://www.danielmoth.com/Blog/2004/10/invoke-cf-and-full-fx.html

Cheers
Daniel

 

[Eric]

I don't know exactly what you mean, here is part of my code:

Public WithEvents prt As SerialPort

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles Button1.Click
SendInit()
End Sub

Private Sub SendInit()
If prt.IsOpen = False Then
prt.Open()
End If

Dim buffer(4) As Byte
Dim ac As Integer
buffer(0) = &H3F
buffer(1) = &H3
buffer(2) = &H7F
buffer(3) = &H9E
buffer(4) = CheckSum(buffer, 3)
prt.Write(buffer, 0, buffer.Length)
End Sub

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load
prt = New SerialPort("COM1", 9600, Parity.Even, 8, 1)
prt.WriteTimeout = 10000
prt.ReadTimeout = 50000
prt.ReceivedBytesThreshold = 3
End Sub

Private Sub prt_DataReceived(ByVal sender As Object, ByVal e As
SerialDataReceivedEventArgs) Handles prt.DataReceived
Dim ab, ac
ab = Me.TextBox1.Text
ab += "data recieved..." + vbCrLf
Me.TextBox1.Text = ab

For ac = 0 To prt.BytesToRead - 1
ab += Hex(prt.ReadByte) + " "
Next
Me.TextBox1.Text = ab
End Sub

Please help me some more?

rg,
Eric

 

[Daniel Moth]

Did you read the link I sent? Please go and read it. The only other piece I
can clarify is that your Data event handler is running on a worker thread.
It is in there where you must Control.Invoke (as my blog entry describes).

Cheers
Daniel

 

[Eric]

yes, I did read it, but I'm not an enough advanced programmer to understand
it, sorry.

Thanks, for your help, by the way.

rg,
Eric

 

[Daniel Moth]

Eric, spend more than 5 minutes looking at the code and you will work it
out. I cannot explain it further. All I (and others) can do here is actually
write the function for you. I prefer to let you work it out since you will
appreciate my help more like that in the long run.

Anyway, here is a skeleton starter

Sub OnUIThread(...)End Sub

Good luck!

Cheers
Daniel

 

[Eric]

Thanks again for you help, but since I don't understand the part about
"invoke", I'll go and take a look at OpenNetCF's version.

rg,
Eric

 

[Eric]

While retyping my little project to OpenNetCF's serialport, I found an
example:

I think what you wanted me to do was:

Private Sub prt_DataReceived(ByVal sender As Object, ByVal e As
SerialDataReceivedEventArgs) handles prt.DataReceived
Me.Invoke( new Eventhandler(addressof ShowData)
End Sub

Sub ShowData(ByVal sender as object, byVal e as EventArgs)
Dim ab, ac
ab = Me.TextBox1.Text
ab += "data recieved..." + vbCrLf
Me.TextBox1.Text = ab

For ac = 0 To prt.BytesToRead - 1
ab += Hex(prt.ReadByte) + " "
Next
Me.TextBox1.Text = ab
End Sub

So basicly, as I understand it, using Invoke will create a new thread and if
the DataRecieved event is hit several times after eachother, it will create
a new thread each time and they will be dealt with by the program in the
order they came?

Is this right?

rg,
Eric

 

[Guest]

OpenNETCF's won't help as the event handler also runs in a worker thread.
You'll still have to use Invoke. Trying to get past that is a disservice to
yourself. Learn how invoke works - this is not the only time you're going
to need it.

-Chris

 

[Guest]

No, Invoke does not create a thread at all. It marshals the call back to
the primary (UI) thread, which is the only process thread that can tough a
UI element. If you get multiple calls to Invoke while others are running,
they get serialized (and you should sync lock them if necessary).

-Chris

 

[Daniel Moth]

Chris covered your misinterpretation of what is going on. I'll repeat, go
read my blog entry *and* the links it points to.

As for your code, yes that should work for you and you could have also
created a different delegate (not eventhandler) so you can pass the e
argument to the method that runs on the UI thread.

Cheers
Daniel