Hi Jonathan, Thanks for the tip Kernel::require 'serialport' does indeed help, very nice! I was calling the program with ruby -rselrialport miniterm.rb , which is not as clean. Unfortunately this does not address the original problem i still get the same error message: C:>ruby miniterm.rb COM9 9600 8 1 (eval):3:in `create': No such file or directory (Errno::ENOENT) from (eval):3:in `new' from miniterm.rb:11 Do you not get this error? Have you modified the source code? Do you think you could send me your .so ? any pointers on how to get this to work would be greatly appreciated! I use both linux and windows and would love to be able to use the same serialport extension for both. Thanks again Eduardo -- Posted via http://www.ruby-forum.com/.