Not receiving reply from syringe pump via rs232 using MSComm1.Input

Question

I am trying to communicate with the syringe pump from PC through rs232.

I want to send a string "02DC;50803" to the pump for establishing the communication and pump should reply "C".

I am using MSComm1.Output="02DC;50803" to send the command and Text1.Text=Text1.Text+MSComm1.Input for receiving. When MSComm1.Output executes I am able to see a LED blinking on the end device but there is no reply using MSComm1.input.

Please help me out with this problem and if I put these instruction under MSComm() control, it seems to be dead.

score 0 · Answer 1 · edited Nov 30 '14 at 02:28

There could be a number of problems here.

For example:

your cable could be broken
your serial port may not be functioning - I see that a lot
Your command is malformed
the pump simply doesn't expect to reply to the command you are sending

Those last 2 might be unlikely, the pump will probably reply to everything you fire at it - all the ones I have here sure answer back.

Really need a lot more information to help you.

What make/model pump?
Manual for the pump so that your commands can be checked.
Have you connected to the pump with an existing software package? - if there is one.

P.S. My software won't support your pump; I don't recognize those commands.

score 0 · Answer 2 · answered Dec 01 '14 at 07:55

To continue the list from timb:

Are you using the correct baudrate?
What are the settings of .RThreshold and .SThreshold?
Are the other comport settings correct (usually N,8,1 but there are exceptions)?
Did you try the command using hyperterminal and get the expected reply?
Where in your code do you read MSComm1.Input? in Which event?
Does the device have a led as well which blinks it is when sending data? does it blink?
Does the command need an end-char like vbCrLf or vbCr of anything else?

Please post the complete code of the function/sub where you send the command, and please post the complete code of the function/sub where you read MSCOmm1.Input

Have a look at the following testproject in which I send the "AT" command to my modem which is connected to commport 1 and with which I communicate at baudrate 9600:

'1 form with:
'  1 textbox control : name=Text1
'  1 command button  : name=Command1
'  1 MSComm control  : name=MSComm1
Option Explicit

Private Sub Command1_Click()
  MSComm1.Output = "at" & vbCrLf
End Sub

Private Sub Form_Load()
  With MSComm1
    If .PortOpen Then .PortOpen = False
    .Settings = "9600,n,8,1"
    .CommPort = 1
    .RThreshold = 1 'read data per char
    .SThreshold = 0 'send all data at once
    .PortOpen = True
  End With 'MSComm1
End Sub

Private Sub Form_Resize()
  Dim sngWidth As Single
  Dim sngCmdHeight As Single
  Dim sngTxtHeight As Single
  sngWidth = ScaleWidth
  sngCmdHeight = 315
  sngTxtHeight = ScaleHeight - sngCmdHeight
  Text1.Move 0, 0, sngWidth, sngTxtHeight
  Command1.Move 0, sngTxtHeight, sngWidth, sngCmdHeight
End Sub

Private Sub MSComm1_OnComm()
  Dim strData As String
  With MSComm1
    Select Case .CommEvent
      Case comEvReceive
        strData = .Input
        ShowData strData
    End Select
  End With 'MSComm1
End Sub

Private Sub ShowData(strData As String)
  With Text1
    .SelStart = Len(.Text)
    .SelText = strData
  End With 'Text1
End Sub

When I click on Command1 it will send "AT" & vbCrLf and the modem replies with "OK" which is shown in Text1.

Not receiving reply from syringe pump via rs232 using MSComm1.Input

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