Setting Communication of Serial Port

- ComPort mean is Port interfacing RS-232 (Com1,Com2)
- Setting mean is Baud,Parity,Data(number of bits),Stop Ex. "1200,n,8,1 "
- HandShaking mean is we can define to 4 type 1.comNone 2.comXonXoff 3. comRTS 4.comTRSXonXoff

Using Buffer for receive and sent data

-InBuffersize mean is define buffer for receive data.
-OutBuffersize mean is define buffer for send data.
- Rthreshold mean is define to occur in Event-driven for send data
- Sthreshold mean is define to occur in Event-driven for receive data
- Inputlen mean is number of data to read in a buffer receive data
- EOFEnable mean is End-Of-File(EOF)

About Hardware

- ParityReplace mean is character value instead of occur Parity Error
- NullDiscard mean is define in receive or not "NULL CHARACTER"
- RTSEnablemean is define signal RTS (Request To Send)
- DTSEnablemean is define signal DTR(Data Terminal Ready)

Define MSComm Control properties to connect port

1. Property CommPort Select comm port that we are using it thus as source code below
Exemple MSComm1.CommPort=1
In this using is Com1

2. Property Settingsmean is setting value for receive /send data that will know baud rate of device which connect ,how much thus as detail below
MSComm1.Settings="Baud(rate for receive/send data),Parity(N,Number of bits,bits Stop"
Exemple  MSComm1.Settings="1200,N,8,1"

3.Property InputLenmean is define input buffer size when data incoming
Exemple  MSComm1.InputLen=1

4. Property PortOpen mean is open port to communucate Open =True ,Close =False
Exemple  MSComm1.PortOpen=True

5. Property Rthresholdmean is do activate occur with Event-driven when has data in receive buffer (comm port) that active the CommEvent in procedure OnComm Event
Exemple  MSComm1.Rthreshold =1

We can using the MSComm properties allow the setting of communication parameters including port selection and port enabling functions. or we will be write to your code
From detail above, we will programming in VB procedure at Sub Form_Load() or create new Sub in case call in the future

Private Sub Form_Load()
       MSComm1.Settings="1200,N,8,1"
       MSComm1.CommPort=1
       MSComm1.InputLen=1
       MSComm1.PortOpen=True
       MSComm1.Rthreshold =1
End Sub

How to communicate with Serial Port
       from progrmming above is define start value to comm port and open port to communicate with RS-232 So, we can get data and send data with Property Output and Input
       Output =send data to serial port
       Input =receive data from port but this will being command to write at Event Property OnComm that has in Sub MSComm_OnComm that read data from serial port or RS-232

Exemple
If we want print data to port while we are typing data to keyborad ,we use event the KeyPress of Control TextBox

Sub txtRXTX_KeyPress(KeyAscii As Integer)
       MSComm1.Output=Chr$(KeyAscii)
End Sub

For Prooerty Input goto Event OnComm

Private Sub MSComm1_OnComm()
Dim StrData As Variant 'define variable type as it is variant
       Str=MSComm1.Input
       Text1.Text=StrData
End Sub

first time i did programming receive data with Property Input if we get direct data from this ,we will get refuse data ,so we may be using a filter function name is DataShow as write thus as below

DataShow function

Public Static Sub DataShow(TextShow As Control, Data As String)
Const SpeedBaud = 16000
Dim LngSize As Long, X
LngSize = Len(TextShow.Text)
If TermSize > SpeedBaud Then
       TextShow.Text = Mid$(TextShow.Text, 4097)
       LngSize = Len(TextShow.Text)
End If
TextShow.SelStart = SpeedBaud
Do
       X = InStr(Data, Chr$(8))
       If X Then
              If X = 1 Then
              TextShow.SelStart = SpeedBaud - 1
              TextShow.SelLength = 1
              Data = Mid$(Data, X + 1)
              Else
       Data = Left$(Data, X - 2) & Mid$(Data, X + 1)
       End If
       End If
Loop While X
Do
       X = InStr(Data, Chr$(10))
       If X Then
       Data = Left$(Data, X - 1) & Mid$(Data, X + 1)
       End If
       Loop While X
       X = 1
       Do
       X = InStr(X, Data, Chr$(13))
       If X Then
       Data = Left$(Data, X) & Chr$(10) & Mid$(Data, X + 1)
       X = X + 1
       End If
Loop While X
TextShow.SelText = Data
TextShow.SelStart = Len(TextShow.Text)
End Sub

Copy code in ListBox below.
Public Static Sub ShowData(TextShow As Control, Data As String) Const SpeedBaud = 16000 Dim LngSize As Long, X LngSize = Len(TextShow.Text) If TermSize > SpeedBaud Then TextShow.Text = Mid$(TextShow.Text, 4097) LngSize = Len(TextShow.Text) End If TextShow.SelStart = SpeedBaud Do X = InStr(Data, Chr$(8)) If X Then If X = 1 Then TextShow.SelStart = SpeedBaud - 1 TextShow.SelLength = 1 Data = Mid$(Data, X + 1) Else Data = Left$(Data, X - 2) & Mid$(Data, X + 1) End If End If Loop While X Do X = InStr(Data, Chr$(10)) If X Then Data = Left$(Data, X - 1) & Mid$(Data, X + 1) End If Loop While X X = 1 Do X = InStr(X, Data, Chr$(13)) If X Then Data = Left$(Data, X) & Chr$(10) & Mid$(Data, X + 1) X = X + 1 End If Loop While X TextShow.SelText = Data TextShow.SelStart = Len(TextShow.Text) End Sub

Call function DataShow :

Call DataShow Text1,(StrConv((StrData),vbUnicode))

      that has character show onTextBox ,about programming in communicate to devices that is receive/sent with Acsii by Serial RS-232 such as load cell ,temperature module we can setting value merely Com Port with its device protocol .

Using Even in OnComm() procedure

this link is table of MS Comm control we get Event in the table to programming in OnComm() procedure with Select case condition as thus code below

Private Sub MSComm1_OnComm()
Select Case MSComm1.CommEvent
       Case comEvReceive
       Dim Buffer As Variant
              Buffer = MSComm1.Input
              ShowData txtRXTX, (StrConv((Buffer), vbUnicode))
       Case comEvSend : 'here put your condition that you want
       Case comEvCTS   
       Case comEvDSR
       Case comEvCD
       Case comEvRing
       Case comEvEOF
       Case comBreak
       Case comCDTO
       Case comCTSTO
       Case comDCB
       Case comDSRTO
       Case comFrame
       Case comOverrun
       Case comRxOver
       Case comRxParity
       Case comTxFull
End Select
End Sub

    I have get exemple program which is control step motor with command Ascii communicate to Micro controller
       A99 ' accelerate setting
       V3 ' speed setting
       D5000 ' step setting
       H- 'direction setting
       G ' go ,it is start motor command
We are assume use a button in my porgram thus as below

    Private Sub Command1_Click()
          MSComm1.Settings="1200,N,8,1"
          MSComm1.CommPort=1
          MSComm1.InputLen=1
          MSComm1.PortOpen=True
          MSComm1.Rthreshold =1
          If MSComm1.PortOpen Then
              MSComm1.Output ="A99 V3 D5000 H- G "  ' character lastest will be press space bar 1 time before put symbo "
          End If
   End Sub

     and this exemple program about MODEM communicate with serial port.

        Private Sub Form_Load()
           Dim strValue As String ' define Buffer value from Modem
           MSComm1.CommPort = 1 ' select Com1
           MSComm1.Settings = "9600,n,8,1" ' setting parameter in communicate with com port
            MSComm1.InputLen = 0 'define size of Input buffer (comming with Modem)
           MSComm1.PortOpen = True ' command open port
           MSComm1.Output = "ATV1Q0" & Chr&(13) 'send AT command to Modem
            Do
             DoEvents
             strValue = strValue & MSComm1.Input    ' get input data of Com Port
              Loop Until InStr(strValue, "OK" & vbCrLf)
              MSComm1.PortOpen = False 'Close port
         End Sub