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Release status: working

PrintrboardRevB Front.jpg
Revision D
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CAD Models
External Link


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.


  • 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)
-- 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.


All preassembled Printrboards come pre-loaded with a bootloader and firmware. You may wish to use alternative (or newer) firmware, modify calibration data for use with another style of RepRap, or perhaps assemble your own board.

To use a Printrboard, you will need to load appropriate USB drivers, either get it from

Compatible Firmware

(Other firmwares are currently untested but any firmware for an arduino mega should work with proper pin setup.)


There is no native Arduino bootloader for the AT90USB series microcontrollers, however, there is excellent opensource support for the MCU and Arduino integration is easily achieved.

  • LUFA's CDC Bootloader: Allows direct uploading of firmware through Arduino/avrude via avr109 protocol. Requires no driver on Linux/Mac and free INF installer to use the built-in Windows driver, and Arduino 022 with modified Teensylu boards configuration. Avrdude within Arduino directory must also be upgraded to newest version. Limited to 64k flash space by the protocol.
  • LUFA's HID Bootloader: No Arduino integration. No drivers required. Allows firmware to be uploaded by command prompt.
  • Atmel's DFU Bootloader: Factory installed bootloader. No Arduino integration. Allows firmware to be uploaded by Atmel's free FLIP software (Windows only). See Teensylu#Sprinter for Mac/Linux equivalent "dfu-programmer".

Installing A Bootloader

If you wish to change to a different bootloader, you will need a USBtinyISP or equivalent ICSP or JTAG programmer. Note that USBTiny only officially supports MCU's with less <= 64K flash (the AT90USB1286 is a 128K chip!). Writing will work with a USBTiny, but read verification will always fail.

  1. Obtain a compiled bootloader (CDC, HID, or DFU). See Lincomatic's Bootloaders for AT90USB1286 article for pre-compiled copies of each bootloader.
  2. Remove the BOOT jumper from the Printrboard. Press the Reset button
  3. Connect the 6 pin programming cable to the Printrboard's ICSP header. Pin 1 (red wire) is closest to the SD card slot.
  4. Connect your programmer's USB cable.
  5. Run the following avrdude commands, where BootloaderNAME_HERE.hex is the name of the Bootloader file you wish to install
avrdude -c usbtiny -p at90usb1286 -U lfuse:w:0xDE:m -U hfuse:w:0x9B:m -U efuse:w:0xF0:m
avrdude -c usbtiny -p at90usb1286 -U flash:w:BootloaderNAME_HERE.hex:i
  1. Replace jumper on the Printrboard. Press Reset again.

WARNING: Triple check the fuse values! Setting incorrect values will brick the microcontroller! Fuse values above are for the CDC and HID bootloaders. Fuses for the factory DFU bootloader should be set as

avrdude -c usbtiny -p at90usb1286 -U lfuse:w:0x5E:m -U hfuse:w:0x99:m -U efuse:w:0xF3:m

Loading Firmware (Windows)

To load new firmware to your Printrboard, first determine which bootloader your board uses. CDC or DFU are most likely.

Printrboard with BOOT jumper removed
Printrboard RevB, BOOT jumper removed

Unlike older AVR microcontrollers, the AT90USB has a special HWB_ALU pin (Hardware Button) which must be tied to ground during a reset cycle in order to place the microcontroller into bootloader mode. This is accomplished by removing a jumper on the Printrboard called "BOOT". Firmware can only be loaded while the chip has booted into its bootloader. Note that on RevD the polarity was changed for the BOOT jumper.

To get into bootloader mode and upload new firmware:

  1. Remove the BOOT jumper (for rev. d/e replace it)
  2. Press and release the Reset button. The AT90USB's bootloader will appear as a new USB device the first time you boot into the bootloader. Allow Windows to install the USB driver and note the new COM port number.
  3. Replace the BOOT jumper onto the board (for rev. d/e remove it)
    Printrboard Running, BOOT jumper in place
    Printrboard RevB Running, BOOT jumper in place
  4. Proceed to upload new firmware using the method relevant to your installed bootloader.
    1. CDC BOOTLOADER (Arduino Bootloader)
      1. In Arduino 022, open firmware
      2. Choose [BootloaderCDC]Teensylu/Printrboard from the Arduino Tools-->Board menu, and select the COM port associated with your Printrboard's bootloader. See Lincomatic's How to Program an AT90USB1286/Teensylu/Printrboard with Arduino article for help configuring Arduino.
      3. Click File --> Upload to Board.
      4. Arduino will compile and upload firmware. You should see an error a few seconds after the firmware compiles. This is because the AT90USB has successfully exited the bootloader.
      5. Press Reset. You may need to disconnect and reconnect the USB and power cables.
      1. Open a command prompt in the directory of the HID application.
      2. Compile firmware within Arduino. You will need to copy and paste the compiled .HEX file into the HID application directory. The HEX file is saved in the temp folder, C:\users\{currentuser}\appdata\temp\build1234567890\Firmware_Name_Here.cpp.hex
      3. Run the hid_bootloader_cli application, specifying your firmware and an mmcu of at90usb1286.
      4. Disconnect and reconnect the USB and power cables.
      1. Open Atmel's FLIP software.
      2. Select the target device: AT90USB1286. Select Communication medium as USB. Click Open.
      3. Compile firmware within Arduino. You will need to copy and paste the compiled .HEX file into the HID application directory. The HEX file is saved in the temp folder, C:\users\{currentuser}\appdata\temp\build1234567890\Firmware_Name_Here.cpp.hex
      4. Open compiled HEX file within the FLIP software.
      5. Make sure the Erase, Blank Check, Program, and Verify checkboxes are checked.
      6. Click the Run button
      7. When finished, disconnect and reconnect the USB and power cables.

Loading Firmware (Linux)


  1. install dfu-programmer (on ubuntu sudo apt-get install dfu-programmer)
  2. compile your firmware as usual with the arduino IDE. (only compile not upload)
  3. arduino will create a hex file within the tmp directory.
  4. power and connect printrboard
  5. set printrboard into boot mode (remove boot jumper, reps after rev.D add boot jumper)
  6. press the reset button
  7. lsusb (should say 'Atmel Corp. at90usb AVR DFU bootloader') if lsusb says 'VOTI' you're not in bootloader mode
  8. sudo dfu-programmer at90usb1286 erase
  9. sudo dfu-programmer at90usb1286 flash {path to the hex file in the /tmp} (e.g. sudo dfu-programmer at90usb1286 flash /tmp/build7750901060806024229.tmp/Repetier.cpp.hex)
  10. exit boot mode by add/removing (depends on rev.) the boot jumper and press the reset button
  11. lsusb should say 'VOTI'
  12. connect with your host software and test if the changes have been applied


Stepper Motors

Connect the X, Y, Z axis, and extruder motors to the matching headers at the top of the Printrboard (X-MOT, Y-MOT, Z-MOT, E-MOT). Headers are 4 wire Molex KK series, part# 0022013047) with 2759 series crimp terminals, part# 0008550101. Motor pinout is:

  1. A - Phase 1+
  2. B - Phase 1-
  3. C - Phase 2+
  4. D - Phase 2-

Note: The two coils in the stepper motor are usually called 1 and 2. The schematic below appears to show pins 1,2,3,4 on the board as 1B,1A,2A,2B. This seems to conflict with the "Motor pinout" description just above.


Usually, one connects a mechanical microswitche to each of the 3-pin Molex headers X-STOP, Y-STOP, Z-STOP at the bottom of the board. The E-STOP header is reserved for future use, but might be treated as an emergency stop by some firmware.

Connect switches as follows:

  1. Switch NC (Normally Closed contact)
  2. No connection (this is +5v out, and not used in this configuration)
  3. Switch COMMON contact

For typical optos, connect:

  1. Signal Output (from the sensor, back to the Printrboard)
  2. +5V (provides power to the sensor)
  3. GND (Ground)


Connect the heating element of your hotend (resistor or nichrome wire) to the 4-pin EXTRUDER header, positioned next to MOSFET Q1. Connect your heatbed to the HOTBED header, next to MOSFET Q2. Polarity here is unimportant.

pinout is as follows:

  1. Positive
  2. Positive
  3. Negative
  4. Negative

Note: The above "pinout" description seems incorrect. Pin 1 is the square pin. Pins 3 and 4 are both +12v power. Pins 1 and 2 are the control to the Hotend and are pulled to ground by the MOSFET, closing the circuit (12v Power through Hotend to Ground), turning the Hotend ON. The pairs of pins (1 and 2 together, and 3 and 4 together) are used to better conduct the high currents required of these "Hot" devices. The Hotbed operates the same way, with the same pinout, from the connector closer to the corner of the Printrboard.


Thermistor headers are 2-pin Molex headers at the right side of the board, located above the reset button.

Connect the heatbed thermistor to the header directly above the reset button. The hotend thermistor connects above the heatbed header.

Lower Power Fan

A 2-pin Molex header labelled FAN is located on the right side of the board, above the thermistor headers. This optional header can be used to power a fan or other small motor. One pin is the +12v supply, and the other is the ON control, pulled to ground whenever the fan should be ON. Generally not used, but some firmware can control this "fan", I believe.

Board Power

Normally, all power is supplied through the 4-pin (2x2) ATX style header on the left edge, near the upper left corner of the Printrboard, labelled PWR. Connect this Power Input directly to any 12VDC power supply of sufficient amperage capability to run the intended devices. For example using a 120 watt hotbed would use 10 amps, all by itself, and more when it is first turned on. The two Ground terminals are closest to the edge of the board (left), and the two 12VDC+ terminals are away from the edge (at the right).

The USBPWR "solder-jumper" is located about half way between the large square micro-processor chip and the two 4-pin connectors for the Hotbed and "extruder". Normally open, it is only used (connected) when it is necessary to use the USB input to supply the Printrboard's Logic with +5v power (when the 12v power input is not being used). Usually, the +5v for the board's logic is supplied by a regulator that is powered by the 12v input, and the open jumper keeps the board's 5v from feeding back into the USB connection.


Connect a micro-USB cable to the USB jack at the bottom of the PCB. Note that a jumper should be installed on the "BOOT" pins for normal operation (see Printrboard#Bootloaders). In revision D, the behavior was inverted so that the jumper is only need when using the bootloader.


EAGLE files for the Printrboard are on Github: [[1]]

Printrboard RevB Schematic

Printrboard RevB Board Layout

Revision History

  • RevA [January 2012]: Internal pre-production design.
  • RevB [February 2012]: First release to manufacturing (RTM), built for first batch of Printrbots. Each stepper driver IC utilizes an SMT solder jumper, MS-X, MS-Y, MS-Z, MS-E to set the microstepping ratio. These jumpers are manually soldered in production and will be eliminated in future batches.
  • RevC [April 2012]: Fixed manufacturability of SMT solder jumpers, MS-X, MS-Y, MS-Z, MS-E. Fixed "printrbot" logo on bottom silkscreen.
  • RevD [June 2012]: Made some more fixes for manufacturability and usability. Also changed the polarity of the BOOT jumper so that the jumper is required only when going into bootloader mode.
  • RevE [July 2012]: (Unofficial release) MOSFET's changed to 70A smt version.

Where to get it

Warning: There is a modified version of the design in circulation that is made with a 2 layer PCB. This modified design is vastly inferior the proper 4-layer design.
Geeetech is one supplier selling the 2-layer boards. There may be others.