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PC Has No RS232 Ports? What to Do?

The Short Answer:

Purchase a “RS232 to USB Adapter” at any office supply store or (typically under $10) and follow the instructions that come with it to install it. (Look for ones that use either a FTDI or Prolific chipset.) After you install it, look in the Windows Device Manager to see what COM Port number was assigned to the adapter (typically COM3, COM4, etc.) and then use it just like a built in RS232 serial port.

The Long Answer:

Although USB stands for “Universal Serial Bus,” the USB interface does not work like old school RS232 serial ports. Like RS232 serial ports, the USB ports on a PC are designed for interfacing external devices. However, any device that is designed to connect to a USB port must come with a Windows device driver that provides a software interface to the device. Practically any device can be designed to connect to a USB port as long as the device is supplied with an appropriate driver.

As a result of the USB interface design, there is no way for a software application to open up a USB port and communicate with any device the same way that you can with a RS232 serial port. Any software that communicates with a particular piece of USB hardware must do so through the driver that was designed to work with the hardware.

Many new laptop computers and some desktop models are now shipped without RS232 serial ports and are equipped with multiple USB ports instead. Fortunately, if you have a device that connects to a RS232 serial port, and you need to connect this device to a PC that does not have any RS232 serial ports, there are many solutions available that are both easy and inexpensive. A number of companies sell single port and multi-port USB to RS232 adapters that connect to a PC through a USB port.

All of these adapters are supplied with a Windows device driver that gets installed on your PC. The device driver software causes the PC to treat the USB to RS232 converter as if it were a built-in RS232 serial port installed on the motherboard of the computer. To accomplish this, the driver for the adapter creates a “Virtual COM port” in Windows that behaves exactly like a physical COM port built into the motherboard.

Single-port USB to RS232 adapters are available at most computer or office supply stores and on line at for under $10. Multi-port add-on adapters also are widely available at reasonable prices. All of these products will work just fine with any Windows-based serial communications software including our WinWedge, TCP-Com, COM-File and BC-Wedge software products.


All you need to do is to:

• Purchase the USB to RS232 adapter
• Install the driver that comes with it
• Plug the adapter into a USB port on your PC
• Determine the COM port number by looking in the Windows Device Manager
• And, finally, connect the RS232 device to the adapter.

The new serial port should be automatically recognized by Windows and assigned a COM port number (typically COM3 or COM4). Even though the new serial port is not built into the system, Windows will treat the port as if it were, and any standard serial communications software will be able to communicate through the port exactly the same way as if it were a built-in COM port.


Although a search on or the Internet for “USB to RS232 Adapter” will turn up dozens of different makes and models, there are two primary companies that make the chipsets and the driver software for the majority of adapters. One is FTDI and the other is Prolific. Both of these companies produce very high quality driver software for all versions of Windows. In addition, if your adapter uses a chipset from one of these companies, and your PC is connected to the Internet, Windows will automatically download and install the driver for the adapter the first time you connect the adapter to a USB port on your PC – literally “plug and play”. Chipsets from other companies may not be as reliable or as easy to install as those from FTDI or Prolific.


The following adapters on are good choices:



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