DigiRig and the TM-D710GA

What logic levels should I be using with Kenwood TM-D710GA.
RS-232 seems to work (but poorly) on 2 applications.
I do have the correct cables.

You got the correct cable and Digirig configuration. If either of those things were incorrect there would be zero chance that you would get any serial CAT control at any point.

Please describe what “poorly working” is like.

FLRIG can see and change the volume and squelch, on either VFO A or B
In the trace mode I see it polling volume and squelch settings also the frequency of the selected VFO. But nothing else like PTT.
WSJT-x can pass the “CAT test” and can toggle the PTT.
PUTTY can take the string “SQ 1 x0D” and will return “SQ nn” where nn is a number indicating the knob position. But there is no line feed or any normal text like operation.
Kenwood’s program MCP-6A shows no attempt at communications.

From this I deduce that the send and receive lines are in the right place, Also that some software is more tolerant of bad voltage levels or is more sensitive to low voltage.

It would be nice to see if anybody can communicate with this radio using DigiRig. I have heard that RT systems can program the radio with their cable and software. I have no idea what their voltage levels are.

I have this setup working with this radio.

MCP-6A won’t work because it expects a serial cable with hardware handshake lines RTS/CTS intact all the way to the radio. DigiRig reroutes RTS to the PTT circuit that grounds PTT in the Digirig’s Audio jack, so it never activates on the serial port. There is no way to disable hardware handshake in the MCP-6A software.

WSJT-X works because you’ve likely selected Default or None for Handshake.

In Flrig, you must have RTS/CTS unchecked in Configure > Xcvr. Also in Flrig Configure > PTT-Generic, select BOTH for RTS under “PTT on CAT Serial Port”. Then in Fldigi Configure > Rig Control > Hardware PTT, check “Use separate serial port for PTT”, select the same serial port that Flrig is using for CAT control, and check “Use RTS”. Also in Fldigi Configure > Rig Control, uncheck “Flrig PTT keys modem” (I assume that you are using Fldigi with Flrig and so already have “Enable flrig xcvr control with fldigi as client” checked on that screen). This setup for Flrig allows PTT to work on whatever side of the radio you have set as your data side, regardless of what side PTT-CTRL is set to.

Also, the current released version of Flrig (2.0.05) does not work well with the TM-D710G. Try the alpha version.

I find the CAT implementations for this radio, Flrig included, frustrating to use because they are dependent on which side of the radio PTT-CTRL is set to. Some time ago, I wrote my own program to control this radio that decouples PTT activation from being side dependent, and only activates PTT on whatever side you’ve designated as the Data side. It allows you to independently manipulate the settings on each side of the radio regardless of where PTT-CTRL is currently set. It also optionally intercepts CAT PTT commands and redirects them to control PTT on the radio’s data port.

Thank you Steve. The next step is for me to get a FTDI based programming cable. I guess I was a bit naive thinking that just because DigiRig sold me a cable for that radio that it would actually work with that radio. Maybe I should send it back for a refund.
Once I can reliably talk to the radio and am able to program it, I will try to use its built in TNC for packet Winlink (or APRS). Then if I decide to keep the radio, I will come back to you for more advice.

Apologies for the delay, I’m trying to get away from the screens on the weekend with various levels of success.

Thanks @AG7GN. I don’t have this radio so the insight from somebody more familiar with it is very helpful.

Re. handshake config:
If the software insists on hardware flow control (use of physical RTS/CTS lines for their original purpose) then indeed it will not work with Digirig’s serial port. These signals allowed to pause the serial communication to give the parties a chance to catch up with the processing. For all practical reasons (due to increased computing capabilities, UART buffers) these signals are obsolete for over 40 years. The only radio that I so far encountered that really needed those was Kenwood TS-570. The decision to not connect RTS/CTS in Digirig allowed for a much the smaller form factor, implementation of a well supported hardware PTT method and more affordable cost of the interface and cables.

Re. use of FlRig/FlDigi:
These are notorious for breaking changes between the versions. It is worth trying several different ones to see if that makes difference.

Re. Digirig configuration and cables:
There is no chance that any communication with any of the software can happen if the configuration of Digirig’s serial port voltages or cables are not matching. If any communication happens then the focus of the troubleshooting can be safely shifted to the software configuration and transceiver settings.

And as always, if you cannot implement what you envisioned you can send any part of all of your Digirig kit back for the refund.