Hi all
I'm building a radio in a box (self contained) and want to implement a PTT from a real microphone. I'm currently using a Udoo pcb and a mini Lime.

Reading the release notes from 3.0.10 https://www.sdr-radio.com/Blog/cid/15?Category=release-notes  it appears I can do this via a USB-serial adapter. If I use a TTL/CMOS level adapter rather than true RS232 levels, I think this will avoid the "what voltage level does the dongle want?" problem.  Such adapters are plentiful on ebay.

I can easily make a small circuit to provide a weak pullup to the mic ptt line and provide some isolation so the TTL/CMOS levels aren't directly exposed to the outside world.

What are other people doing for bringing inn external PTT? 

Thanks
Barry WØIY