SerialPort.ReadChar() takes hex returns decimal

[nx2ms]

Hi there,

I am working on a simple vb project to read data from a PC serial port and write that data to a file.

The data is ascii sent in Hex format. I used MySerialPort.ReadChar() to read data and MyStreamWriter.Write(MySerialPort.ReadChar()) to write it to a file.

I copied my code below, sorry about the format.

The trouble is: MySerialPort.ReadChar() acts the same as MySerialPort.ReadByte() , both takes the Hex data input and returns data in decimal format.
I tried to use Convert.ToChar(MySerialPort.ReadChar()) to covert decimal to char, but it's too slow.
I tried decimal.ToChar(MySerialPort.ReadChar()), but VB doesn't recognize decimal.ToChar, even after I installed .NET4.

Did I do something wrong? how to make MySerialPort.ReadChar() to read Hex data and return char?

Please help..

nx2ms


Entire code is here: sorry about the format.
******************************************************

Imports System
Imports System.IO
Imports System.IO.Ports
Imports System.Text


Public Class Form2

Dim WithEvents ComPort As SerialPort =
New SerialPort("COM3", 9600, Parity.Even, 8, StopBits.One)


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

If ComPort.IsOpen = False Then ComPort.Open()
MessageBox.Show(ComPort.BaudRate & ComPort.PortName & ComPort.Parity & ComPort.StopBits)
End Sub

Private Sub ComPort_DataReceived(ByVal sender As Object, ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) Handles ComPort.DataReceived


Dim path As String = "C:\Users\blu\My Documents\work\Projects\VB_Uart\Uart_Test\test8.txt"

Dim objWriter As New System.IO.StreamWriter(path, True)

'objWriter.WriteLine(Hex(ComPort.ReadByte()))
objWriter.WriteLine(ComPort.ReadChar())
'objWriter.WriteLine(ComPort.ReadByte())
'objWriter.Write(Convert.ToChar(ComPort.ReadByte()))
objWriter.Close()


End Sub


End Class

[dbasnett]

"The data is ascii sent in Hex format." means what exactly? Hex is an Ascii interpretation of ones and zeros stored in memory. The data is actually stored and sent in binary, how we interpret the binary is up to us.

        Dim c As Char = "Z"c
        Dim a As Byte = Convert.ToByte(c) 'get c as it is stored numerically
        Debug.WriteLine(c)
        Debug.WriteLine(a.ToString) 'show the decimal value
        Debug.WriteLine(a.ToString("X").PadLeft(2, "0"c)) 'how c looks in memory as hex
        Debug.WriteLine(Convert.ToString(a, 2).PadLeft(8, "0"c)) 'how c looks in memory as binary

[nx2ms]

You are right Hex part is not that critical.

The data is made of 0's and 1's, is intended to be interpreted as Ascii.

Do you have any suggestions as why MySerialPort.ReadChar() behaves same as MySerialPort.ReadByte(), both return data in decimal format?

Thanks.

[dbasnett]

You are right Hex part is not that critical.

The data is made of 0's and 1's, is intended to be interpreted as Ascii.

Do you have any suggestions as why MySerialPort.ReadChar() behaves same as MySerialPort.ReadByte(), both return data in decimal format?

Thanks.

Then interpret the data as ascii. I'd use .Read.

        Dim foobar() As Byte = New Byte() {90} 'what you received from the rs232 port
        Dim c As String = System.Text.ASCIIEncoding.ASCII.GetChars(foobar, 0, foobar.Length)

'or

        Dim foobar As Integer = 90  'what you received from the rs232 port
        Dim c As Char = Chr(foobar)

[Shaggy Hiker]

A character IS a byte fundamentally. Technically, we now have two byte characters in some encodings, but not for serial purposes. A byte is always binary. It's up to you whether you want to see it as decimal, hex, or interpret it into an ASCII character. All three of those are different visual representations of the same eight bits. The bits aren't any different just because you choose to interpret them as a decimal number or a string character. Having said that, I should also add that you want to keep them as numbers as long as possible, because once you put them into a string or character datatype, they are slower to work with.

[nx2ms]

Thanks for the reply. I understand what you guys try to say. I tried Chr() in my code, it works well.

My issue here is the speed. When I used putty to receive data, it can take 8x more data than using VB SerialPort.ReadChar(), with Chr(dec), or Convert.ToChar(dec), those two are about same speed. I originally thought the decimal to char conversion slows down the data transmission. Then I realized MySerialPort.ReadByte() runs about same speed as well.

So maybe batch processing i.e. reading from a buffer would improve more? Any suggestions?

Thanks for your help, I really appreciate.

[nx2ms]

Thanks guys, I used SerialPort.ReadLine(), it's now cooking with gas... great!!

[Shaggy Hiker]

Yeah, reading into a buffer should boost your speed. ReadByte is going to have to get each byte sequentially, which is ok, but when you fill a buffer, the compiler can use some memory copying techniques that should greatly boost your performance. Fill a buffer whenever that option appears viable, and don't convert things into strings until the last possible moment. If you get a byte array buffer, leave it as a byte array, and work with it as a byte array, as long as you possibly can. Manipulating strings is slower than working with bytes, as a general rule.

[nx2ms]

I see, in data format is easier to process. Now I just use StreamWriter.WriteLine(SerialPort.ReadLine()) everything is ASCII, VB may treat it as a string. Anyway to read a buffer as data?

Thanks for your help.