How do I Read Serial Port

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1.00/5 (1 vote)

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Hi,
I am using the following Visual Bascic 2010 code to read a numeric sting value from a com port. My question is how can I adapt the code to read a second string from the same com port ? I can add a letter or number at the start of the string if required. Monitoring the code coming off a arduino Due board at the serial port shows the streams in the folowing way.

67.7 51.2
67.6 51.3

The code I am using to read the port is the following (see below)

Thank you for any assistance.
Regards
Nevjc

VB

Delegate Sub myMethodDelegate(ByVal [text] As String)
Dim myDelegate As New myMethodDelegate(AddressOf ProcessReading)

Private Sub SerialPort_DataReceived(ByVal sender As Object, ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) Handles sp.DataReceived
   Dim str As String = sp.ReadLine()
   Invoke(myDelegate, str)
End Sub

Sub ProcessReading(input As String)
   If IsNumeric(input) Then
      temperature = CDbl(input)
      picTherm.Refresh()
   End If
End Sub

Posted 26-Mar-14 7:46am

Member 10701701

Updated 27-Mar-14 2:36am

Rage

v3

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Comments

[no name] 26-Mar-14 14:53pm

What is a numeric string? It's a string. Why can't you sp.ReadLine() again to read a second string?

Member 10701701 27-Mar-14 5:55am

Hi,
Thanks for your comment. I have to admit I am a complete novice at this and do not know visual basic code. I would appreciate any help. The two streams of code come off an Arduino board to a USB port and are shown by the serial monitor in the following form
67.7 51.2
67.6 51.3
Thank you for your help
Nevjc

[no name] 27-Mar-14 7:41am

Okay.... and? Did you add another call to sp.ReadLine so you could read another line from the serial port yet? Did it work or didn't it?

Member 10701701 27-Mar-14 7:55am

Hi,
I added : sp.ReadLine() to the readline but it did not work continuosly it seems to read the second string occasionaly or otherwise blank.
Thanks for the help.

[no name] 27-Mar-14 8:55am

Well you are only going to get data out of the port if there is actually data in the port to read....

Sergey Alexandrovich Kryukov 26-Mar-14 15:06pm

It depends on what do you call "VB", exactly.
—SA

Member 10701701 27-Mar-14 5:57am

Hi,
Thanks for your comment. I have to admit I am a complete novice at this and I am using Visual Basic 2010 Express. I would appreciate any help. The two streams of code come off an Arduino board to a USB port and are shown by the serial monitor in the following form
67.7 51.2
67.6 51.3
Thank you for your help
Nevjc

Sergey Alexandrovich Kryukov 27-Mar-14 10:26am

You need to use System.IO.Ports.SerialPort. Where is that in your code?
—SA

Sergey Alexandrovich Kryukov 27-Mar-14 10:37am

Could you move all the code to the body of the question, to have it properly formatted?
And what, not a separate thread for the port communications?
—SA

Member 10701701 27-Mar-14 10:41am

It appears okay now
Nevjc

Member 10701701 27-Mar-14 14:32pm

Hi added 1 substring as per suggestion. Code works 20% of the time and displays number but comes up with the folowing error

A first chance exception of type 'System.ArgumentOutOfRangeException' occurred in mscorlib.dll

My altered code

Delegate Sub myMethodDelegate(ByVal text As String)
Dim myDelegate As New myMethodDelegate(AddressOf ProcessReading)

Private Sub SerialPort_DataReceived(ByVal sender As Object, ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) Handles sp.DataReceived
Dim onestr As String = sp.ReadLine()
Dim twostr As String
twostr = onestr.Substring(0, 4)
Invoke(myDelegate, onestr)
End Sub
Sub ProcessReading(ByVal input As String)
If IsNumeric(input) Then
temperature = CDbl(input)
picTherm.Refresh()
Label1.Text = CDbl(input)
Label2.Text = CDbl(input) * 2
End If
End Sub

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Rage · Accepted Answer · 2014-03-27T02:40:00

Solution 1

Assuming you have two values per String, you will have to parse each string for the two values:

Assuming:

Line 1: 67.7 51.2 
Line 2: 67.6 51.3 
etc..

Then:
a. Trim the white spaces
b. Separate the string into substrings by divding it at every blankspaces
c. Convert each substring into value as in the example.

Posted 27-Mar-14 2:40am

Rage

Updated 27-Mar-14 4:27am

v2

Comments

Member 10701701 27-Mar-14 10:26am

Thanks for that I will give it a go.

Thanks for the help Nevjc