How might I retrieve the port number of a USB device that is connected to a USB port?

问题

How might I retrieve the port number of a USB device that is connected to a USB port, using VB6? I can already get the USB Device name, let's say: \\?\USB#Vid_0801&Pid_2250#7&91e2848&0&1#{4d36e978-e325-11ce-bfc1-08002be10318}

How do I automatically detect what port number is assigned to it? I am making a program that will automatically determine the port number of a specific device attached to any of the USB port and start communicating on it automatically.

回答1:

to view the available comports you can use :

'1 form with :
'    1 combobox : name=Combo1
'    1 mscomm control : name=MSComm1

Option Explicit

Public Enum PortAttr
  PortFree = 0
  PortInUse = 1
  PortUnknown = 2
End Enum

Private Sub Form_Load()
  'show available ports
  ShowPorts
End Sub

Private Sub ShowPorts()
  Dim intIndex As Integer
  Dim intPort As Integer
  Dim intFree As Integer
  On Error GoTo ErrorFound
  With MSComm1
    If .PortOpen Then .PortOpen = False
    intPort = .CommPort
    Combo1.Clear
    Combo1.AddItem "--- Not Used ---"
    Combo1.ItemData(0) = -2 'not possible
    Combo1.AddItem "---- In Use ----"
    Combo1.ItemData(1) = -2 'not possible
    intFree = 0
    For intIndex = 1 To 10
      Select Case CheckPort(intIndex)
        Case PortFree
          intFree = intFree + 1
          Combo1.AddItem "Com" & CStr(intIndex), intFree
          Combo1.ItemData(intFree) = intIndex
        Case PortInUse
          Combo1.AddItem "Com" & CStr(intIndex)
      End Select
    Next intIndex
    If .PortOpen Then .PortOpen = False
    .CommPort = intPort
    If CheckPort(intPort) = PortFree Then
      If .PortOpen = False Then .PortOpen = True
    End If
  End With 'MSComm1
Exit Sub
ErrorFound:
  MsgBox Err.Description, vbCritical, "Error " & CStr(Err.Number)
  On Error GoTo 0
End Sub

Private Function CheckPort(intPort As Integer) As PortAttr
  On Error GoTo ErrorFound
  With MSComm1
    If .PortOpen Then .PortOpen = False
    .CommPort = intPort
    .PortOpen = True
    CheckPort = PortFree
    If .PortOpen = False Then .PortOpen = True
  End With 'MSComm1
Exit Function
ErrorFound:
  Select Case Err.Number
    Case 8002 'port doesnt exist
      CheckPort = PortUnknown
    Case 8005 'port already in use
      CheckPort = PortInUse
  End Select
  On Error GoTo 0
End Function

in that list you can mark the ports which you already know, so the others should be the port from the usb device

pay attention : when the usb device is connected through another usb port, the converted rs232 port might be a different one as well

回答2:

This guy has some useful scripts: http://todbot.com/blog/2012/03/02/listcomports-windows-command-line-tool-for-usb-to-serial/

来源：https://stackoverflow.com/questions/9661612/how-might-i-retrieve-the-port-number-of-a-usb-device-that-is-connected-to-a-usb

标签

vb6

usb