AutomationDirect Logo USB to RS-232C serial adapter Frequently Asked Questions



Product Selected: USB to RS-232C serial adapter
Category Selected: Communications

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Question: Is there a USB port for programming on the PLC?
Answer: No, only serial ports or an optional ethernet port.
FAQ ID: 1032
Question: How do I connect to the PLC when I have no serial port?
Answer: Use a USB-to-serial adapter for a PC that has no built-in serial port.
FAQ ID: 1033
Question: Why can't I connect to the PLC with the USB-to-serial adapter?
Answer: 1) A USB-to-serial adapter generally requires a driver to be installed, either available from disk or download. Once that is done, the adapter should be seen with an assigned COM port in Windows Device Manager.

2) Assuming that the driver assigned the USB-to-serial converter a PC COM port number other than 1 or 2, as an example, we'll assume that most of the time COM4 is assigned. (You can check this assignment in Device Manager under Ports, COM and LPT.)

In DSLaunch, under Utilities, the last selection is DS500.INI. (In older versions, DS400.INI or DS300.INI may be used. Any of these files would be located in the main C:/WINDOWS or C:/WINNT directory.)

Double click on that, and when it opens in a text editor, drag the scroll bar about half-way down to the section where you'll see:

COM1ENABLE = 1
COM2ENABLE = 1
COM3ENABLE = 0
COM4ENABLE = 0
.....

Change the setting to equal 1 for any port you want to use, (COM4ENABLE, in this case,) and save the file. Close DSLaunch and Directsoft (both), (and LookoutDirect and DSData, should you have them open,) and re-open so they can read the changed INI file.

COM 4 should now be available for creating a link.

Do this accordingly for COM 3 through 8. If the assigned number is higher, it usually means that the system is not really using that COM port number, and it can be re-assigned in the port Properties to a lower number, such as 4. (2 and 3 are often assigned as the default for a modem, and should be checked before being used as the re-assignment number.)

3) Some USB adapters are known to have problems with our software, specifically Targus or Quatech. (See application note AN-DS-002.pdf, page 4.)
FAQ ID: 1034