[RSM] Serial Port Testing Question

[Jack Parker]

Hi, again, Jessy:

I was finally able to acquire the bits and pieces needed to build the 
loop-back plug and verify my USB/serial adapter is functioning. The 
adapter and extension cable are fine but when I attached the cable to 
the TS-570D serial port it did not respond as expected. In looking at 
the data sent to and received back from the TS-570D ("FA;" sent and 
should have received the '570s frequency back) I saw there is no reply 
to the query. That sure does point to a non-robust RS-232 port on the 
TS-570D! 🙂 I tried data rates set to 4800/8/N/2 and 9600/8/N/1 with 
both DTR and RTS set to "handshake" but that did not help.

There was one curious thing found when N1MM logger was configured for my 
rig. As expected, N1MM did not see the rig upon boot-up of the program. 
The frequency displayed was the default 14200.00 for 20-meter SSB. I 
decided to turn the rig off and back on while N1MM was running and, to 
my great surprise, I saw the correct rig frequency displayed even though 
N1MM still said it did not detect the rig. When the frequency of the rig 
was changed no update was sent to N1MM but the frequency was refreshed 
if the rig was turned off and back on. It appears I may have diagnosed 
the nature failure in the serial port. That would be the "FA;" command 
not being received by the rig while the rig automatically sends the 
frequency data string when powering up verifying the  data line from the 
rig to the computer is functioning when there is a command to send. That 
is not of much assistance because it's doubtful the serial port could be 
repaired in the field, especially by someone who no longer has the tools 
to do the job. At this point about the only thing I could hope to do is 
figure out a way to manually tell the '570 to send frequency data like 
it does on power-up.

That's where matter stand at present. Thanks for your assistance!

73,

On 1/26/2026 3:35 PM, Jessy Blanchette wrote:
> 100% correct on a straight through cable.  If you have a null modem 
> cable (crossover) it's for connecting PC's to each other (DTE data 
> terminal equipment).
>
> If you do have a null modem cable in the junk box you can test serial 
> ports between serial ports on a PC (like COM1 to COM2)  with putty on 
> each comm port.
>
> I would be very surprised if the serial port on the rig isn't working 
> -- rs232 is pretty robust.
>
> On Mon, 26 Jan 2026 at 14:20, Jack Parker <vhfplus at gmail.com> wrote:
>
>     Tried PuTTY and it did not work. I must find a DB9 connector and
>     build a loop-back test jig. AFIK the radio/PC cable should be a
>     straight-through. Lots of bad info on the "interweb". ;)
>
>     I'll keep plugging away at this and hope the TS-570D's serial port
>     is okay.
>
>     Thanks and 73,
>
>     On 1/25/2026 2:47 PM, Jessy Blanchette wrote:
>>     Your welcome!
>>
>>     Another quick tip,  on the rs232 adapter or physical serial port
>>     on the PC you can also do a "loopback test" jumping the TX and RX
>>     lines together.  When the rx / tx serial lines are looped
>>     ,whatever you type in Putty will echo back right away -- then you
>>     know the host/pc serial port working ;)   If it's a one wire
>>     test, make sure hardware flow control is disabled in Putty.
>>
>>     https://www.instructables.com/DB-9-RS-232-Loopback-Plug-Windows-and-OS-X/
>>      overkill tutorial, but explains this in more detail.
>>
>>     73 es GL!
>>
-- 
Jack, VA4JP/K0JP
Steinbach, MB
EN19pm