Features

• Atmel AT90USB1286 Microcontroller (or AT90USB1287 drop-in compatible for 20mhz support)
• Native USB interface. No FTDI serial-to-USB chip!-- 128kb Flash
• Four integrated Allegro A4982 Stepper Drivers (no Pololus needed)

• On-board 4-channel DAC to control stepper set current (Rev F)
• Thermistor Connectivity: 2
• 2 N-MOSFETs for Extruder and Heatbed control
• 1 N-MOSFET for low power Fan or motor
• Onboard SD card slot
• Four Endstop connectors supplied @ 5V. Includes X, Y, Z, and fourth endstop called E-Stop to be used as an emergency stop, or extruder stop (to be added in firmware).
• Supports multiple power configurations (Carried from Sanguinololu)
• Logic & Motors supplied by ATX or laptop power supply (12-20V 120W minimum)-- Logic supplied by USB bus (if enabled by solder jumper)-- Logic supplied by on-board voltage regulator-- on-board USB connectivity
• Edge connectors enabling right-angle connections

• Dedicated I2C connector (Rev F)
• FET-based buffer for Z-endstop to support 12V inductive bed sensors (Rev F4)
• 14 Extra pins available for expansion and development, with the following capabilities
• UART1 (RX and TX)-- SPI (MOSI, MISO, SCK)-- PWM pin (1)-- Analog I/O (6)-- JTAG (uses some of the ADC pins)

• Additional 14 pin header with remaining I/O for prototyping
• SMT Components sized at 0805, and no QFNs for easier soldering.
• 4-Layer PCB with proper ground plane and power distribution networks
• Small design - board is 100mm x 60mm (4" x 2.4")