[nos-bbs] More on these RTS based PTT circuits everywhere

M Langelaar maiko at pcsinternet.ca
Mon Feb 1 05:10:48 EST 2021

I did some searching Bob and it would appear that some PC manufacturers
and some USB to RS232 controllers actually invert the logic of their serial
ports for the default rest state. I am using a Dell Optiplex with Windows 7,
and quite honestly it's usually a Dell even on my linux systems. That's how
I burned out my Tekk Data Radio a few years ago. JNOS crashed and I had
not had the watchdog component of my circuit built at the time (I did after
the incident).

I even read a post where a guy has requested a 'invert RTS' option. I often
wonder why nobody else has said anything about these posts. I'm not making
this stuff up, it's very consistent, and that's why I'm going through 
all this trouble.

I mean who needs to come home and find their radio smoked cause a program
crashed. In my case anyways, and it would appear also for the guy who came
up with the circuit in the link I provided where he put in the BS170 


On 01/02/2021 3:41 a.m., M Langelaar wrote:
> Well there in lies the problem. my rest RTS is always high, interesting.
> What computer model do you have, and version of O/S.
> On 31/01/2021 10:07 p.m., Boudewijn (Bob) Tenty wrote:
>> I have the RTS line connected via an resistor to the anode of the 
>> diode inside the Optocoupler, with the cathode in there
>> connected to ground. In rest RTS is negative.  When I activate PTT in 
>> FLdigi, WSJTX, etc. RTS goes positive and Optocoupler
>> pulls PTT to ground and operates TX as you said. If I quite my 
>> programs like the above, RTS just remains negative, no tx is 
>> triggered here
>> after that.  No problem here.
>>> converts negative logic to positive ...
>> That is the only thing I shouldn't  have said as RTS is using NRZ.
>> Bob VE3TOK
>> On 2021-01-31 21:25, M Langelaar wrote:
>>> Hey Bob,
>>>> In those other 100s of circuits the Optocoupler already
>>>> converts negative logic to positive ...
>>> How ? why then when I quite most of my programs like winmor,
>>> or WinRPR, optocoupler is energized and PTT is taken to ground
>>> and TX is triggered, unless I'm missing something really obvious :(
>>> Maiko

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