Arduino Mega as panel interface

Yes, any sserial daughtercard is supported by LinuxCNC
(because sserial cards are self describing to LinuxCNC/HAL)

Nice!
Then I wonder what's the advantage of the 7i69 compared to the 7i90HD.
The 7i90 has more I/O and is cheaper...

I added the 7I90HD to the "Remote Serial Daughter Cards" section

Thanks!
Could also fit into this category: "Anything I/O Cards --> Remote Serial Daughter Cards"