The Teensy is a complete USB-based microcontoller development system, in a very small footprint, capable of implementing many types of projects. All programming is done via the USB port. No special programmer is needed, only a standard "Mini-B" USB cable. The Teensy Loader program communicates with your Teensy board when the HalfKay bootloader is running, so you can download new programs and run them. The Teensy Loader is available in a command line version to automate programming, typically using a Makefile. This contains only the cli version of the Teensy Loader. To run it type: teensy_loader_cli.