Hi Jonathan,
Welcome on board!
The basic answer is that CAT is an integral component of the RemoteRig system. All you need to do is to
connect the rig's CAT to the RRC's COM2 and configure COM2 in both RRC's. I have never done this for an
857, but this is how I think you need to go about it:
1) Make up and install a cable between the 857's CAT port and the standard DB9 connector used for COM2 on the radio RRC
2) Change the CAT rate on the 857 to the rate desired by your software (menu 19). I recommend keeping it as low as possible,
i.e. 4800 or 9600 baud to keep traffic over the internet to a minimum and faster is not necessary for CAT.
3) Change the COM2 serial settings of the radio-RRC to mode-4, using the baud rate set in the 857, then submit/apply changes.
4) Install the Microbit Setup Manager if you already haven't. This installs the correct drivers on your PC.
5) Change the COM2 serial settings of the control-RRC to mode-4, using the same baud rate set in the 857 and radio-RRC,
then also set "use USB Com Port as COM2" to "Yes" and submit/apply changes.
6) Plug in a USB cable between your PC and control-RRC. Make sure you do NOT do his before step 4 above!
7) Find out the correct port in your Windows Device Manager to use by looking for the "Microbit RRC Virtual COM Port (COM2)"
Set your CAT control software to use the this COM port on your PC using the baud rate set in the 857 and both RRC's
73,
Mitch DJ0QN / K7DX