Setting up a Serial TNC with GPS on HSP cable

This interface type is for standard converse-mode TNCs that have only one serial port, but you have a Hardware Serial Port adapter that splits your serial port in two so you can attach a GPS to it as well as the TNC.

For interfaces of this type, Xastir will poll the serial port for GPS data by setting the DTR pin of the serial port. The HSP circuit will shunt the GPS data in and block the TNC data while DTR is asserted. Xastir will then unset the DTR pin and start receiving TNC data again.

You probably don't have this setup, as it's a very 90s solution to very 90s hardware. But if you do, press on.

• Except for one extra check box, this is exactly the same setup as a Serial TNC.
• Set System Clock from GPS Data?: This is that extra check box. If checked, allow Xastir to set the system time from the extremely accurate GPS clock. Xastir has to be running SUID root for this to work.