See the DigiUSB→Echo example and the applications in the “Digispark - Example Programs” folder for an example of how to use the DigiUSB library.

On the computer side you can use the included command line tools in the DigiUSB Programs folder:

• If you're on windows make sure to install the DigiUSB driver in that folder (different from the main Digispark driver)

• digiusb - this program is like the Arduino serial monitor, allowing you to send and receive messages to/from a Digispark running DigiUSB
• send - this allows you to send data/text to a Digispark with DigiUSB - run with –help to see all options
• receive- this allows you to receive data/text from a Digispark with DigiUSB - run with –help to see all options

Also check out the ruby gem: http://rubygems.org/gems/digiusb