[Xastir] Setup with a Kenwood TM-D710A

[Liz]

I think I've got radio / computer communication, with some packets
logged on the TNC and some on the interface.
However, my GPS connection through the radio is a failure.
Can someone summarise for me 
1 how I should set the radio for GPS > Xastir
2 what the startup config should be for GPS > Xastir

I think I have tried multiple combinations so far without success.

The GPS attached to the radio works fine to the radio
If I put a GPS dongle on the computer I can connect to its port
(/dev/ttyACM0) and Xastir can use that data.