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USB to RS232 adapter for PTT switching, help needed finding one.

Posted: 07 Jan 2017, 15:01
by ghost123uk
Hi all, I am intending to have a go at simple Packet Radio, likely using PSK31, on 11Mtrs (It's legal to do this now, on certain frequencies)

I have got it all set up and working on both RX and TX using a very nice bit of software called fldigi, which is easy to install via the Linux repositories (yes, I use Linux (Mint)). All it requires is suitable attenuation of the RX and more so, the TX audio so as to be able to use the computers sound card. I have done that and got the levels correct.

However, for now, I'm having to manually switch between RX and TX using a basic toggle switch :roll: because I cannot source a USB to serial port adapter, with a relay (or solid state switch) to operate the rigs PTT. The fldigi software toggles the RTS and DTR pins of an RS232 (Serial) port, so I need a board / adapter that simulates an RS232 and has a buffered output of the RTS and / or DTR pins (as the standard current capability of an RS232 is insufficient, I believe).

Now I have spent hours trying to find such a thing, with no success. This surprised me as I would have thought there would be quire a demand for such a thing, not just for radio, but for other applications.

Can anyone assist ?

Re: USB to RS232 adapter for PTT switching, help needed finding one.

Posted: 07 Jan 2017, 17:14
by ch25
DIY http://mixw.net/img/serialcon_t.gif and you can use current usb converter
Or http://sigma-shop.com/product/100/usb-r ... -chip.html should do the trick.

Re: USB to RS232 adapter for PTT switching, help needed finding one.

Posted: 08 Jan 2017, 08:58
by ghost123uk
ch25 wrote:DIY http://mixw.net/img/serialcon_t.gif and you can use current usb converter

The DIY bit looks simple enough, however, the unit I have now does not have physical 9 pin connections. It is a virtual com port and the relay(s) are driven by HEX commands, not simple RTS and DTR pins high/low inputs. This applies to the one you linked to below, making it unsuitable for use with fldigi type software.



I'm really surprised these are virtually impossible to find :?

It looks like I will have to order a USB to a "real" RS232 port, and make up that simple transistor switch. Thanks for the diagram :)