
Chapter 19: Wireless Wide-Area Networking
Virtual Serial Port
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Psion Mobile Devices Developers Guide
19.4.2.1 Using the Virtual Serial Port
The WWAN driver provides a virtual serial port so that other applications such as Windows CE dial-up
networking can access the WWAN modem concurrently with the WWAN user interface. The main purpose is
to support dial-up data connections in a more convenient manner. The virtual serial port offers a number
of advantages over direct access to the serial port:
• The WWAN driver does not need to be shut down in order to establish a dial-up data connection.
• The WWAN driver and user interface provide the PIN handling.
• For all GSM/GPRS modems the APN for the virtual port can be automatically configured through the
WWAN user interface.
• The WWAND/jointfilesconvert/334834/bg utility can be used to analyze the AT commands sent by legacy third-party applications.
19.4.2.2 Configuration
The virtual serial port is available as COM8: with the name Virtual WWAN port. The port is created dynam-
ically if a WWAN modem is present and the modem initialization was successful (including successful PIN
authentication, if required). The virtual port should be configured as follows:
• Any baud rate (this setting is ignored, the correct baud rate for the modem is chosen by the
WWAN driver).
• 8 data bits, no parity, 1 stop bit.
• No flow control (flow control for communication with the modem is handled by the WWAN driver).
19.4.2.3 AT Commands
The virtual serial port can be used by an application to send AT commands to the modems. Since AT
command sets differ between modems, a detailed knowledge of the modem in question is required. There-
fore, this use of the virtual port should be limited to legacy applications. New applications should use the
Mobile Devices SDK to access the network status, SMS functions, etc.
The Option Globetrotter (v1, v2, Combo) and Sierra AC775 do not forward unsolicited AT command
responses (e.g. “+CREG:” responses that were enabled with “AT+CREG=1”) to the virtual port.
For the Enfora ADT0110 and GSM0110, Siemens MC75, Option Globetrotter (v1, v2, Combo), as well as Sierra
AC775 it is possible to send AT commands to the modem while a packet data connection through the
WWAN driver is active; however, for the Option Globetrotter (v1, v2, Combo) a transition of the emulated
DTR signal on the virtual port closes that packet data connection.
When porting legacy applications, the virtual serial port together with WWAND/jointfilesconvert/334834/bg utility can be used to
analyze the AT commands sent by that application. With the debug level set to 6, all AT commands are
shown in the log.
19.4.2.4 Entering AT Commands in Windows CE
To enter modem AT commands on a Windows CE device, you first need to create and open a console
window, as described in the following steps:
1. Go to Start > Settings > Network...
2. Double-click on the Make New Connection icon.
3. Enter a name for the new console connection in the text box.
4. Click the Next button (leave the connection type as Dial-Up Connection.
5. In the Select a modem drop-down box, select Virtual WWAN port.
6. Click the Configure button.
7. S e t Flow Control to None, and leave the other Connection Preference settings at their
default values.
8. Check the Use terminal window before dialing check box.
9. Click OK to close the Device Properties window.
10. Click the Next button.
11. Enter an arbitrary value (e.g. 1) for the Phone number text box.
12. Click the Finish button to complete the connection configuration.
13. Back on the Network... screen, double-click the icon for your newly created connection.
14. Click the Connect button. The terminal window will open after a few seconds.
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