DOCUMENT:Q209077 16-NOV-2001 [vbwin] TITLE :PRB: CommCtl: No "OK" Received When Using Some Modems PRODUCT :Microsoft Visual Basic for Windows PROD/VER::3.0 OPER/SYS: KEYWORDS:kbToolkit kbVBp500 kbVBp600 kbOSWinCEsearch kbGrpDSVB kbGrpDSVBDB ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft eMbedded Visual Basic, version 3.0 - Microsoft Windows CE Toolkit for Visual Basic 6.0 ------------------------------------------------------------------------------- SYMPTOMS ======== Some modems may not respond with an OK in the Input string of the Communications control when an AT command has been sent. CAUSE ===== Modems may not respond if the Data Terminal Ready (DTR) signal is low. You may need to raise the DTR signal before opening the Communications port. Note that the Communication control only checks the DTREnable property when the port is being opened. If the DTREnable property is set to True after opening the port, the DTR signal does not change until the port is closed and reopened. RESOLUTION ========== To get the modem to respond with an OK, set the DTREnable property of the Communication control to True prior to opening the communications port. NOTE: This will not necessarily work for all modems. STATUS ====== This behavior is by design. MORE INFORMATION ================ Steps to Reproduce Behavior --------------------------- 1. Create a new Windows CE project in either Visual Basic or eMbedded Visual Basic. Form1 is created by default. 2. From the Project menu, choose Components. In the Components dialog box, click the Controls tab, then select the Microsoft CE Comm Control. 3. Place a command button (named Command1), a text box (named Text1) and a Comm control (named Comm1) on Form1. 4. Paste the following code into Form1: Option Explicit Dim InBuff Private Sub Comm1_OnComm() If Comm1.CommEvent = comEvReceive Then InBuff = InBuff & Comm1.Input Text1.Text = InBuff End If End Sub Private Sub Command1_Click() Comm1.RTSEnable = True Comm1.Settings = "9600,n,8,1" Comm1.RThreshold = 1 Comm1.SThreshold = 1 Comm1.CommPort = 2 Comm1.PortOpen = True Comm1.Output = "AT" & vbCrLf End Sub Private Sub Form_Unload(Cancel As Integer) Comm1.PortOpen = False End Sub 5. Run the project on the device. RESULTS: The OK does not come back from the modem. REFERENCES ========== Microsoft eMbedded Visual Basic 3.0 Online Help Microsoft Windows CE Toolkit for Visual Basic 6.0 Online Help Additional query words: kbdse vbce evb vbce6 ====================================================================== Keywords : kbToolkit kbVBp500 kbVBp600 kbOSWinCEsearch kbGrpDSVB kbGrpDSVBDB Technology : kbVBSearch kbAudDeveloper kbZNotKeyword2 kbVBeMbSearch kbWinCETKVBSearch kbWinCESearch kbVBeMb300 Version : :3.0 Issue type : kbprb ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. Copyright Microsoft Corporation 2001.