Automation in Amateur Radio: RS-232 for local and remote applications

 If you are a modern radio ham, you deal much with the RS-232 Serial standard.

High-Frequency ham gear has had a computer interface since at least the 1990s.    The common name for this interface is Computer-Aided Transceiver -- CAT -- a term coined by Yaesu I believe.      Using the CAT interface, one can read or change the frequency of the radio, change bands, and adjust the majority of controls found on the faceplate of the radio.

CAT is a "staple", and the minimum level of automation for both local and remote control of an amateur station.   Some modern radios use USB (The Universal Serial Bus) for CAT.   USB is bit harder to automate in remote situations, but not impossible.

Beyond CAT control of the radio, there is control of other auxiliary components in the station -- amplifiers, rotators, antenna switches, and keying mechanisms for CW/PTT.

RS-232 and the modern Windows computer

In order to interface your radio or other peripheral to your PC, be it a laptop or desktop, you need to have an RS-232 port.   Since the mid 2000s, most PCs do not have a built-in RS-232 port.   Typically, an RS-232 port is installed by either installing a PC card in a slot in the computer or by using something called a USB-to-RS-232 cable.

A Typical USB-to-RS232 cable

This is the most common type of RS-232 Interface.   The USB "becomes" a serial port because embedded in the cable is a conversion chip.   A software driver, either a default one provided by Windows or provided by the driver manufacturer, enables the port and it shows up in the Windows Device Manager, with a specific COM port number:


Typically, these USB-to-Serial cables come from a variety of manufactures, with a wide variance in quality.  Typically, chipsets made by FTDI are the most stable.   However, these one-off USB Serial cables can be fraught with trouble.

One problem that happens is that once the USB Serial cable has been installed, it's COM port number is attached to the physical USB connection where the cable is plugged in.  In fact, a "reservation" for this COM port number is held for the physical serial port, even if the cable is removed.   If by accident, you plug the cable into a different USB connector, a new COM port assignment will be made for the same physical cable, typically confusing the user, and tieing up two COM port numbers.   Over time, a computer will get polluted with many COM-port reservations, even if only one USB-to-serial exists.   This situation gets worse when more than one serial port cable is used.

Unfortunately, it's not simple to "clear" these COM port reservations.  Windows has no built-in mechanism to do this.   Luckily, however, a nice programmer named  Uwe Sieber out there in Internet land decided to write a utility to fix the problem easily.    You can download the tool here.      Note that if you are using Windows 7 or later, after downloading, you'll have to right-click on the file, choose Properties from the menu, and check the "Unblock" checkbox.   Otherwise, Windows may not allow you to run the files inside the ZIP file.

Inside the ZIP file, you'll find ComNameArbiterTool.exe in both 32-bit and 64-bit flavors.  Run the appropriate version for your PC.   If running the 64-bit version, it must be run with elevated execution privileges.   This is done by right-clicking on the EXE and choosing "Run as Administrator...".    Once you do this, you'll see the interface:

The ComNameArbiterTool.

Now, your PC will probably have many fewer entries than mine.     I recommend unplugging any USB COM ports before running this tool.  Then, run the tool and press both buttons.   This will remove all NON-present COM ports.   After this process, plug in the ports you have, and note the COM port numbers.   DO NOT MOVE USB Serial ports between different USB Slot positions on your PC, or you may end up in COM port hell again!

There must be a better way!

As our amateur stations become more and more complex, we have the need for more and more serial ports.  I can attest to many hours of futzing with all manner of USB Serial ports!   I wanted to find something better.

It turns out that RS-232 is BIG in the commercial world.   Many manufacturers have been producing rock-solid USB-to-RS232 interfaces for many years.   Are they plagued with the same issues we have as hams?  I should hope not.  I have been involved with a few of these companies in my work in software engineering.   One is Digi, the other, Lantronix.   These companies make USB-to-Serial products as well as what are called serial (or terminal) IP Servers.   The latter allows the creation of virtual serial ports over an IP network -- either in your shack or across the Internet.  I'll discuss those later on in this post.

It turns out that the Digi USB-to-Serial boxes are not cheap.   New prices, on a device that has four serial ports, are in the $300 range on Amazon!   Your typical ham is not going to spend that much on four RS-232 ports!

The good news is these products have been around for decades, and, with surplus outlets such as eBay, these devices are available to hams at very reasonable prices.

The Digi Edgeport Series

The Edgeport product line from Digi has been around for a long time.   It consists of 1, 2, 4, 8, or 16 RS-232 serial ports in the DB9 or DB25 connector form factor.    These are USB bus-powered devices, and typically come in an off-white plastic box:


The Digi Edgeport/4 4-port DB9 Device
The Digi EdgePort/4 DB-25 device


The Edgeport/16 is a 1U rack server, providing 16 DB9 serial ports
from an 

What makes the Edgeport products better than the rest?

Like many good hardware products, it's the software drivers that make all the difference.
Though the Edgeport boxes will be automatically be recognized by Windows, the Digi driver is highly recommended.   The driver is available here. (It is an EXE download.)   It is recommended you install the driver BEFORE connecting your Edgeport device.

After the driver is installed, run the EdgePort Configuration Utility:

The Edgeport Configuration Utility

When you plug in your EdgePort, it will automatically be detected by the utility.  COM port numbers will be automatically assigned, but these can be changed via the Configure button.

One of the most important settings available is the Advanced settings tab:


Advanced Settings tab for Edgeport Configuration

NOTE the "COM Port Assignment: Based on converter serial number" option. This option, when set, will make the COM port assignments STICKY to the box -- you can plug the box in anywhere, and the port numbers will remain the same.

More on Port Servers coming....




                                    

















 

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