I fixed the serial port in nsvip/nsnova and Saitek OSA a few days ago, it's pretty fun to experiment with.

eg. mame.exe leonardo -rs232 terminal -numscreens 2
Set the screen views in video options, set the baudrate, disable the chesscomputer keyboard.

Yep, I saw this, but I guess that's one more feature not usable in my MAME 0.220.
I've compared the current drivers for rs232 with the old ones in 0.220, but they are so different, that I didn't even try to updated all the files from devices\bus\rs232 to my old version (when not even such a simple clock driver like msm5001n is working anymore).
I was even wondering that these engines nsvip/nsnova did compile and run at all with the old rs232 drivers after your latest changes ...

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