Hardware recommendations for VMC retrofit:

The odroid to 7i92 is a cat5 connection.

7i92 connects to 7i77 a number of ways depending on the middle you get; direct 25pin connection or db25 cable or db25 ribbon cable.

The 7i77 connects to the 7i84 or 73 via modified cat5.

I would keep the 7i92 and 7i77 in the cabinet. There will be a lot of wiring to connect to them. You also want to have a short distance between the two as possible. I think the recommended is less than 3m. The 7i92 can connect to two daughter cards via 25pin or 26 pin. So technically you could run a 7i77 and a 7i76 (not a great combo for most machines but this would give you 6 analog axis, 5 step, a spindle and dozens of io). Each daughter card could also run a serial card 7i84 or 7i73 etc. With it being in the cabinet this leaves you a ton of options for io that will be needed for actual machine function.

The odroid at the console will save you running connections back from it to the monitor and keyboard. And you can run a cat 5 from the odroid to the 7i92 in the 5m distance with little issues but I would keep this as short as you can also.

For a card in the console their are a lot of options. Tommy may be more correct with a 7i73 but it all depends on setup and what you want to do. Literally a dozen mesa serial cards that could work. The 7i84 has input and output. You most likely don't need outputs in the console. Either way the serial card in the console saves on wiring back to the 7i77 in the cabinet as it would just need a single cat5.

Here are some serial card options:
store.mesanet.com/index.php?route=product/category&path=69_70

Can I ditch the 7i92 completely and just plug the 7i77 into the Odroid like you would with a 7i76E?

The 7i77 has enough inputs and outputs for the cabinet, and the 7i84 or 7i73 would have plenty for the console

I need more io than what the 7i97 has. Can i plug a generic breakout board into the 7i97 for more io, as well as 7i84 for the console.

I will only need 4 analog servo drives + spindle. Will this free up more io ports?

Or am I best just to accpt that I'm going to need 3 mesa cards?

The only reason I'm going for the 7i84 over 7i73 is it has the terminal blocks instead of just a header

I would suggest a 7I92H +7I77+7I84 because its older and supported by pncconf

Thanks PCW.

What cable is required to go from 7i92H to 7i77?

Mesa DB25M-HDR26 or similar