12.1. Setting Communication Port

  1. First and foremost is to check for serial port availability, engineer who's using Ethernet connection could skip to next step. Nowadays most laptops and PCs do not equipped with COM port and USB to Serial converter is needed to emulate COM port. COM port only allows single application to be occupied at any one time. To test if the COM port driver is successfully installed, open up Hyper Terminal from Windows Start menu \ Acccesorries \ Communications. Check that the desired COM port is available as one of the option for connection.

    COM 1 is available for connection


    Bottom left corner showing 'Connected' status. Note that this only means the port has been successfully open but doesn't mean Hyper Terminal has started communicating with any external devices.


    [Important] Important

    Ensure Hyper Terminal is disconnected or closed after confirming the availability of port. Otherwise it may occuppied the port and obstruct other programs.

  2. Ensure physical connectivity is the most essential step. Try to use device supplied programming software or third party software to establish the communication between targeted PC and device. For instance, third party OPC server could be used for polling to confirm that the physical link is properly connected.

    Serial link requires communication parameters to be exactly matched between SCADA and devices. Engineer must confirm the parameter settings in the devices and configure exactly the same for server, i.e. Baud Rate, Data Size, Parity & Stop Bit. e.g. 9600 8 none 1.

    TCP/IP link would be very much easier to setup as compare to serial link. Anyhow both of them still need to configure the node address and eventually a list of data address. Engineer must know the configured node address for the device and the available list of data address and its data type, and again they must be exactly matched. Before the communication is established, only one integer data address should be entered in order to avoid confusion.

    [Important] Important

    Ensure all tools and programs that opened for testing are closed before proceeding to the next step.

  3. Always try to narrow down the scope of the troubleshooting. Avoid having any converter in between, unless it's inevitable.

  4. If the programming tool or third party software managed to establish the communication, it's pretty clear that the problem is within the configuration. Firstly, open up the server GUI, click on the IO Task, and check out its status log. If there's any problem in the communication, an exclamation mark shall appear next to the IO icon in the Task Window. And red text describing the error shall be logged. If too many messages are logged, click on Clear Task Status to remove old messages, then click on Restart Task to start up IO again. And latest IO status shall appear in the status log.

    IO task must be checked during communication troubleshooting