www.dl2rum.de

I just upgraded the station computer to a new M4 iMac. The previous was an M1 MacBook Air.

I had been using using the FTDI serial cable available from Elecraft to connect to my KX3. It works fine, but is USB-A instead of USB-C as used on the more recent Apple, and I guess other, computers. So, I thought to change the serial adaptor to simplify things and make it all prettier instead of using the Elecraft FTDI serial cable adaptor and a short USB-C to USB-A cable.

So, I bought one of these:

Adafruit FTDI Serial TTL USB Type C cable

It doesn't work with either RUMlogNG or WSJT-X.

Yeah, the device shows up in the Settings panel on both. It shows up in the macOS System report. If I connect an oscilloscope to the transmit line and send messages through CoolTerm, I can see the levels toggling as they should. If I connect RXD to TXD anything I type into CoolTerm gets echoed back to the CoolTerm panel.

Anybody have any idea of what I might be doing wrong with this cable? Or, does anybody have a suggestion for a good alternative?

Maybe your Elecraft requires RS232 level, not just TTL?

That is a good thought, but according to N6KR:

"The input can accept the full RS232 range, +/- 25 V. But 0-5 V will
also work. In fact 0-3 V will work."

I'd think he would know, but he made that comment early on in KX3 production and things could have changed.

I'll keep looking.

Well, you were right, in a way.

It wasn't the levels. It's that RS-232 is inverted TTL, at least for Elecraft radios. I found a comment to that effect buried in a forum from years ago.

But, I learned that FTDI based USB to serial parts can be easily programmed. (And, bricked I'm told.) FTDI offers a free application to read the EEPROM and program them. Most of these USB to serial solutions are capable of a lot more than they usually are programmed for. Anyway, two check boxes and another push to program button had RXD and TXD inverted in seconds.

Seems to work now with the 3.3 V logic levels.

When I looked at the EEPROM values in the FTDI USB-A to RS-232 cable that I bought from Elecraft, I saw that neither TXD nor RXD are inverted. The RS-232 interface chip must do that function. So, it's a good thing that you sent me off to research the RS-232 part - thanks!

The only bad thing is the FTDI Programming app is only for Windows computers. Thankfully I have a late model Intel iMac on the workbench that runs Windows 10 in Boot Camp that I use with test gear.

I think an awful lot of hams have bought USB to serial cables that didn't work with their radios because the logic was inverted. Easy fix, if you know to look.