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

[Boudewijn (Bob) Tenty]

Maiko,

In those other 100s of circuits the Optocoupler already converts negative logic to positive, so I don't think the extra expense of a Mosfet is needed.
You also need a +5V line..I just use a simple, cheap RCA connector at that side of my interface.  :-)

Bob VE3TOK

On 2021-01-30 09:57, M Langelaar wrote:
> Last post about this, sorry everyone, but it's been very educational though.
>
> I have a good friend who knows SERIAL I/O as if he has a PhD on it, he
> really knows his stuff, having engineered and had an alarm company for
> decades with serial and gpio style annunciators and communications.
>
> I didn't really give this much thought, but actually - if you think about it,
> when a program terminates in Windows, the com ports are 'given back'
> to windows and put into their 'default state'. The signals from the UART
> go through inventors, so really the RTS 'high' should be expected.
>
> One solution perhaps is put a BS170 small signal MOSFET  inverter
> between the RTS pin (really RTS negative) and change the logic of
> the program software so that rts_active(Yes) actually means OFF,
> and rts_active(No) actually means ON, easy enough for the perl
> script.
>
> I actually did find ONE drawing online that matches this method, so all of
> these RTS PTT circuits (100s of them) online are really not the way to do
> it, in our opinion anyways, just my 2 cents worth ...
>
>    circuit can be found here -> http://ganymedeham.blogspot.com/2017/12
>
> The CM108 (Jose sent me a link, you can search it up), pretty cool, and not
> as expensive as I originally realized, is an option I will look into. BUT I actually
> do use RTS quite a lot for my other projects, so that is really why I came up
> with the solution.
>
> Maiko / VE4KLM
>
> On 28/01/2021 11:39 p.m., VE4KLM wrote:
>
>> One disclaimer of sorts.
>>
>> RTS line for PTT can be 'dangerous' to your RIG, you need to be paying
>> attention when the PERL script has terminated. I have observed this even
>> with WinRPR and other software based modems. RTS will go high when
>> any of those programs exit, resulting in your PTT staying on !!!!
>>
>> So what I do is disconnect my PTT before terminating any programs,
>> yeah I know, it's like back to the future, or city on the edge of forever.
>>
>> I'm sure there is circuit mod I can do to solve this ...
>
>
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