Serial port will not communicate

Third-Party Software Issues


Most often, serial port communication issues are caused by software that is installed on the Field PC. You may want to try uninstalling and re-installing the software. Or you can try resetting the Field PC, restoring the operating system to a previously saved state, or setting the operating system to factory defaults. For instructions, please visit our website starting at:


Reset System


Testing the Serial Port


If you feel the serial port on the Field PC is not communicating, the serial COM ports on newer Windows-based Field PCs can be tested using Microsoft ActiveSync. If you have a DOS-based Field PC, the serial port can be tested using the Lynx file transfer program. For more information about ActiveSync or Lynx, please refer to the Field PC user`s manual.


Terminal Software Testing


The most basic method for testing serial COM port communications is using a terminal application on the Field PC and desktop PC to communicate with each other. Make sure ActiveSync or any other program is disabled from using the serial port before continuing. To perform this test, follow these steps:


  1. Connect a 9-pin RS-232 null modem serial cable between COM1 on the Field PC and the 9-pin serial port on the desktop PC.
  2. On the Field PC, start the terminal application. If one is not already installed, you can download and install a third-party terminal software program onto the Field PC (such as Cambridge Software vxHPC).
  3. Every terminal program is different. Using the built-in Terminal program on older Windows CE Allegro models, tap on Start > Programs > Communications > Terminal, and then double-tap on the "Make New Session" icon.
  4. Enter any Session name as desired, select "Hayes Compatible on COM1" as the modem, set phone number to "1" or any number, and then tap on the Configure button.
  5. In the Device Properties (Configure) window, set the Port Settings to be similar to the COM port settings in Hyper-Terminal on the desktop PC, or record the current settings in Terminal so you can later set Hyper-Terminal to match these settings.
  6. Tap on the "Manual Dial (user supplies dial strings)" checkbox to select this setting, and then tap OK to close the Device Properties window.
  7. Tap OK on the Session Properties window. A white, blank terminal window will appear on the Field PC. Leave the Field PC in this state.
  8. On the desktop PC, click on Start > Programs or All Programs > Accessories > Communications > Hyper-Terminal.
  9. In the Connection Description window, enter any name for the session, and then click OK.
  10. In the Connect To window, select the COM port (usually COM1) that you will be using on the desktop PC. If you do not know the desktop PC`s COM port number, you can find it in the desktop PC`s Control Panel under Hardware > Device Manager. Once you have selected the COM port, click OK.
  11. In the Port Settings window, enter the settings to match exactly the Port Settings in Terminal on the Field PC, and then click OK.


You will be taken to a white, blank window similar to the one currently on the Field PC. Try typing any keyboard characters on the Field PC or desktop PC and the same characters should appear in the white screen on the other device. If this is the case, then the serial port hardware on the Field PC and desktop PC are functioning properly.


ActiveSync Issues


If you are having issues with communicating through the serial port using ActiveSync or a similar program, please visit our ActiveSync Connection issues FAQ website, or follow the step-by-step instructions provided on our ActiveSync COM port connection FAQ website. You may want to consider using an alternative connection method.


Power Off or Extended Power Removal


Performing a full Power Off (available on models running Microsoft Windows Mobile) and/or removing the battery pack and any external power source (wall charger) for 20 minutes or longer may reset hardware, causing the issue to no longer be produced.


Reseat or Replace Communication (I/O) Module


If the RS-232 serial port appears to be damaged or no other solution above seems to help, some Field PC models (such as the Mesa, TK6000, and Archer) have a Communication (I/O) Module Replacement Kit to allow ports to be replaced in the field. Please check with your local reseller or repair center about possibly purchasing one of these kits.


Request a Repair


If no replacement kit is available for your Field PC model, or the port is still not working after replacing the Communication (I/O) Module, you can submit a repair order to Request an RMA.