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

[M Langelaar]

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 ...