VB.net text file STX, ETX

[vishalkbhatt]

Hi friends, I am working on an application in which I have to send a data of a text file to a PLC machine. Now the convention is that
send start of file (0x02)
send data bytes (file data)
send end of file (0x03)

Now I dont have any idea that how to send the STX and ETX before and after the file data respectively. The PLC should receive them as 02 and 03 i.e. in their Hex values. If there is any ready function like vbCrLf for STX and ETX or any other way to achieve this then please reply . Thank you

[dbasnett]

        Dim buff() As Byte = New Byte() {2, 3} 'STX, ETX

        SerialPort1.Write(buff, 0, buff.Length)

[vishalkbhatt]

Thanks for ur reply.. but what I want is
<STX> file data <ETX>
Your following line :
SerialPort1.Write(buff, 0, buff.Length)
writes the entire buff array which is : Dim buff() As Byte = New Byte() {2, 3} 'STX, ETX on serial port. so what shud be the modification to send only STX first then file data and then ETX on the serial port??

Thanks again
Vishal ...

[dbasnett]

Something like this

        'test file data
        Dim ipsum As String = "Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum."

        Dim bytesAsList As New List(Of Byte)

        bytesAsList.Add(2) 'stx
        bytesAsList.AddRange(System.Text.ASCIIEncoding.ASCII.GetBytes(ipsum)) 'the data
        bytesAsList.Add(3) 'etx

        Dim buff() As Byte = bytesAsList.ToArray 'as byte array

[DickGrier]

The straight forward way is,

Dim Packet(datalength + 2) As Byte
Packet(0) = 2
Packet(1) = firstdatabyte
'continue adding data bytes through
Packet(datalength) = lastdatabyte
Packet(datalength + 1) = 3
SerialPort.Write(Packet, Packet.Length)

Generally, the data to the PLC might be binary, not ASCII text (though some PLCs do employ string commands). If your PLC is expecting ASCII data (text) commands, preceeded by STX and terminated by ETX, you can use dbasnett's suggestion. Simpler is just:

Dim myASCIIData As String
myASCIIData = somestringcommand
SerialPort.Write(Chr(2) & myASCIIData & Chr(3))

Dick

[dbasnett]

The straight forward way is,

Dim Packet(datalength + 2) As Byte
Packet(0) = 2
Packet(1) = firstdatabyte
'continue adding data bytes through
Packet(datalength) = lastdatabyte
Packet(datalength + 1) = 3
SerialPort.Write(Packet, Packet.Length)

Generally, the data to the PLC might be binary, not ASCII text (though some PLCs do employ string commands). If your PLC is expecting ASCII data (text) commands, preceeded by STX and terminated by ETX, you can use dbasnett's suggestion. Simpler is just:

Dim myASCIIData As String
myASCIIData = somestringcommand
SerialPort.Write(Chr(2) & myASCIIData & Chr(3))

Dick

Sorry for the confusion. I used the ascii data as an example of byte data.

        Dim PRNG As New Random

        Dim randData(PRNG.Next(32, 65)) As Byte 'create a random sized buffer as a TEST

        PRNG.NextBytes(randData) 'fill the TEST buffer with TEST data

        Dim someData As New List(Of Byte) 'construct output buffer

        someData.Add(2) 'add stx

        someData.AddRange(randData) 'add the random data

        someData.Add(3) 'add etx

        Debug.WriteLine(randData.Length.ToString)
        randData = someData.ToArray 'convert list to array
        Debug.WriteLine(randData.Length.ToString)

I think the method I would choose would depend on the format of the data, and if it were fixed length or not.