This is a project that is based on Sanguinololu. The ATmega644P has been replaced with an Atmel AT90USB1286 MCU. This Microcontroller has onboard USB, removing the need for the FTDI USB UART. Additionally all of the through hole resistors and capacitors have been replaced with 0805 SMT components, with the exception of 4 parts which are 0603 (as of REV 0.1) The board size is smaller to reduce cost, and overall part count is less than the Sanguinololu. Like the Sanguinololu the Teensylu has expansion headers supporting I2C, SPI, UART, as well as a 6 ADC pins.