I use USB-RS-232 converters. Its cheap (9.95¤) and works great.

You can select from COM1 until COM256.

COM1..COM4 can also be used from old DOS programs under Windows-XP.

But the only difference to a direct COM, there is a long delay and a big buffer inside.

So for fast data transmission it is suggested to send large blocks.

E.g. for my bootloader I use blocks of 512 bytes.


Peter