You can get USB->Serial converters which work well on the Mac.
If you write your code in such a way that allows you to compile it for the three platforms, it should work fine.
I've got a working cross-platform serial module (tested on Mac, Linux and Win32) using the same high-level API, so it's perfectly doable.
The tricky bit is accessing the various system APIs/ports, but once you have the line opened, it's all pretty much the same everywhere.
Good luck! :-)
If you write your code in such a way that allows you to compile it for the three platforms, it should work fine.
I've got a working cross-platform serial module (tested on Mac, Linux and Win32) using the same high-level API, so it's perfectly doable.
The tricky bit is accessing the various system APIs/ports, but once you have the line opened, it's all pretty much the same everywhere.
Good luck! :-)