Printrboard

Overview

The Printrboard electronic set was designed by members of the Printrbot team in order to eliminate the production and functionality shortcomings of older RepRap electronics sets. Printrboard improves upon the previous production-grade electronics set (Gen6) by adding heatbed and SD card support, reverting to 1/16 microstepping Allegro stepper drivers, and improving connectivity reliability and reducing cost by elimination of the FTDI UART chip. Printrboard also has expansion headers supporting I2C, SPI, UART, and ADC pins. All extra I/O ports of the AT90USB have been broken out to headers for prototyping and expansion. Printrboard is a derivative of Teensylu, an AT90USB1286 development board originally based on Sanguinololu. The Atmel AT90USB1286 MCU has on-chip USB, removing the need for the FTDI UART (USB-to-serial) IC. On-chip USB means dramatically faster firmware upload times and communication. The AT90USB connects at any baud rate regardless of firmware configuration, and operates virtually free of serial communication errors/pauses.

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) 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 14 Extra pins available for expansion and development, with the following capabilities -- UART1 (RX and TX) -- I2C (SDA and SCL) -- 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")

Benefits of this Design

Utilizes integrated Allegro 1/16 micro-stepping drivers for smooth operation. Integrated USB controller provides 12MBps bandwidth, instead of usual 38400-115200 baud via FTDI. Result: Virtually no serial communication errors (common with Sanguinololu and Generation_6_Electronics). Integrated micro-SD Card slot Uses small standard Molex connectors for motors, heater, and endstops. Lowest cost and greatest performance of all RepRap motherboards at time of release, March 2012.