Re: Serial cable question

Benny Miller <bmiller@...>

Steve - K9DCI,

Usually they will be enumerated in sequence. Some laptops 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 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.

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.

I hope that this helps and clears up what you may see.


Ben ARS w4qed

Quod erat demonstrandum!
That which was to be demonstrated!

-----Original Message-----
From: TMD700A@... [mailto:TMD700A@...] On Behalf Of
Sent: Sunday, March 29, 2009 10:55 PM
To: TMD700A@...
Subject: [TMD700A] Re: Serial cable question


You've got to know the answer to this question.

I'm doing Serial I/O on a PC with a serial port, called COM1. I do memory
management and real time control of several radios, including the D700,
using Excel. (See the Files area).

I just got a new PC with 4 USBs. Aside from the USB<>Serial adapter
functionality issue (which is critical for me), How do I know which COM
numbers are assigned to the USB ports. Is it going to be 1, 2, 3, 4 or some
other numbers...?

73, Steve, K9DCI
It's critical because on two of the radios (706 & TH-F6A) I steal power from
the serial port for the level conversion circuitry.


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