Here is some thoughts I had today on USB Serial ports. The question posed was what COM port number will be assigned to a USB  Serial Port Adapter?
Usually they will be enumerated in sequence. Some laptops & computers have COM port 3 or 4 reserved for a modem so that one will be bypassed.
Now for the unusual, if using Linux OS then once you have USB Hubs and serial adapters connected they probably will remain in the correct order /dev/STTY4.. Even if you change USB hubs it should still enumerate correctly.
NOTE: the side USB port (hub) on a Laptop is not the same USB hub as the rear ports usually.
Now in Windows if you change the placement (USB port) of the serial adapter it will enumerate on a different COM port most of the time, unless you happen to plug it in manually in a certain order and then that isn’t guaranteed to enumerate correctly.
In windows, pull up the START->CONTROL PANEL->SYSTEM->HARDWARE MANAGER and expand PORTS. As you plug in each adapter watch which one is enumerated in the COM port recognition sequence. Remember if you change the Adapter on to a different hub it will probably get a different COM port number, sometimes not but it can and at times will happen. Then you need to recognize that the port has changed and you’ll need to assign ports every once in awhile. Mine are usually stable on the Main computer, but I have to watch on the laptop.
Many times in windows, pull up the START->CONTROL PANEL->SYSTEM->HARDWARE MANAGER and expand PORTS you are able to actually manually change the COM port assignment by going to the Properties in the particular port.
Some additional information not particulary related to the above:
I use several different off brand of USB to serial adapters but no Belkins tried here as yet. Only USB problem I’ve had with drivers has been trying to use two of the same make of USB Cameras, computer gets confused once in awhile. I do not have 2 or more of the same USB to serial adaptors either.
I’m constantly switching USB to serial adaptors from main system to laptop. I really like the Signalink USB; although, I think it could be better on transmit I use on yet another computer that has my MagicJack on it (24/7). It receives far better than it seems to transmit; then again it could be my TM-D700a’s receive sensitivity in the car or my short height on my home antenna with the rolling hills of Georgia.
Currently using FT-470, FT-100D, TM-D700a, TH-D7ag, FT-2800 and finally a RS 10 meter transceiver with a pk-232. All rigs setup for digital operation of one type or another. Is D-Star next? Who knows what the next b-day will bring.
I usually have several serial cables hanging around here at the house and the major problem I had was the wrong connectors and having to use adapters for m/m or f/f. A standard USB to serial cable (USB-1200) seemed to work just fine on the TM-d700a with a sex change adapter. The adapter made things rather stick out a bit since it is mounted under the dash on the floor. Next installation, next car, will orientate the cables and antenna connections a different direction.
So if you have a USB Serial port Adapter and it won’t work for you, then just send it to me. I may be able to use it or at least use parts for a project around here.
73’s,
Ben –
w4qed
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