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Release status: working

20131116113208-IMG 6530.jpg
Creative-Commons 3.0 CC BY-SA
CAD Models
External Link


SAV MkI power connector detail
SAV MkI power connector detail

This 3D printer board electronics has been designed and developed using all the great contributions and feedback from the RepRap CloneWars group in Spain. All shortcomings from other similar boards have been addressed providing an affordable yet feature rich 3D printer electronics. The SAV MkI, improves upon the previous production-grade electronics set (Gen6, sanguinololu) by adding well dimensioned power MOSFETS, SD card support, on-board regulated 3.3V to connect to 3.3V level peripherals such us Bluetooth, as well as improving on USB link's reliability and reducing cost by eliminating the FTDI UART chip.

The SAV MkI is a derivative of Teensylu and the Printrboard, an AT90USB1286 development board originally based on Sanguinololu. The Atmel AT90USB1286 MCU has an on-chip USB, removing the need for the FTDI UART (USB-to-serial) IC. On-chip USB means that you will get faster firmware upload times, communications, g-code transfer and reduce the time file transfers take from the host to the on-board microSD card. The AT90USB connects at any baud rate regardless of firmware configuration, and operates virtually free of serial communication errors/pauses.

20131116113208-IMG 6530.jpg

In addition, the SAV MkI has broken out the second UART with its levels adjusted to 3.3V logic. You will be able to connect any HC-05 or HC-06 bluetooth dongle to wirelessly control your printer.


Feature rich yet affordable 3d printer electronics. The SAV MkI has been designed after taking feedback from the Clone Wars RepRapers out there. We have come through with an electronics that we believe will meet your expectations.

  • Hotend and heatbed well dimensioned FETs that can take up to 15A without heat-sinks.
  • High speed native USB interface connectivity going up to 12Mbps so that there is no lag on your prints.
  • 12V built-in fan controller for your layer fan or hot end cooling.
  • Micro SD reader for autonomous printing.
  • Bluetooth dongle (dongle not provided, tested with HC-05 and HC-06) interface adapted to its logic levels for wireless operation.
  • Expansion bus to connect a keyboard and LCD.
  • Support for 4 standard pololu compatible stepper motor drivers.

SAV MkI connections




Atmel AT90USB1286 Microcontroller @16 MHz

  • Native USB interface
  • Flash: 128KB
  • RAM: 16KB
  • EEPROM: 128KB

Supply: 4.2V to 5.5V

Voltage input


Internal regulated voltage

5V and 3.3V

Logic supplied by on-board voltage regulator through Vin Logic can also be supplied through USB (internal source selection).


  • Edge connectors enabling right-angle connections
  • 2 x 15A switching connectors with high power N-MOSFETs.
  • 1 x switching N-MOSFET for low power fan.
  • 2 x 12V outputs 1.5A max load.
  • 1 x on-board uSD connector
  • Bluetooth interface output levels adjusted for 3.3V logic (connected to UART1 - Rx and Tx).
  • 4 x Endstop connectors supplied @ 5V. Includes X, Y, Z and E
  • 2 x Thermistors
  • 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)

LCD support

The board supports any LCD designed for the printrboard, teensylu or sanguinololu.

We have also designed an LCD for it with rotary encoder, 2 push buttons and an extension backpack to allow you to connect a 5V device (for example, a servo for your bed auto level) with an IO pin and its own regulated 5V output.

Check it out.






SAV MkI housing
SAV MkI housing

SAV MkI box with integrated fan SAV MkI enclosure

SAV MkI dimensions
SAV MkI dimensions

SW, Firmware and SDK

All preassembled SAV-MkI come pre-loaded with a bootloader and Marlin firmware. You may also upgrade the firmware, modify calibration data for use with another style of RepRap, or perhaps assemble your own board.


  • Marlin (pre-loaded) - Marlin's main branch already supports the SAV-MkI (MOTHERBOARD==83) or (#define MOTHERBOARD BOARD_SAV_MKI, on Marlin 1.1.x).
  • Bootloader: LUFA's CDC Bootloader
  • SDK: Arduino IDE with Teensy add-on.
  • Windows users only, will need to install USB Serial device (will be downloaded with the Teensy environment).

To use a SAV MkI, you will need to load appropriate USB drivers, you can get them from:

Compatible Firmware

  • Marlin Marlin: Official support, use (MOTHERBOARD==83) or (#define MOTHERBOARD BOARD_SAV_MKI, on Marlin 1.1.x).
    • Pre-configured version of Marlin for the SAV MkI. Use the released versions which have been tested, the main branch at times may contain experimental code.
  • Repetier List_of_Firmware#Repetier-Firmware: No support yet.

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

Setting-up the environment

The instructions here will help you setup the development environment using Arduino´s IDE version 1.0.6. Currently working in getting it going on Arduino 1.6.5.

Step 1: Download and install the Arduino IDE

Download the Arduino 1.0.6 development environment if you don't have it already. [Arduino]

Step 2: Download and install Teensyduino

Teensyduino was created by PJRC for their Teensy line of boards. Teensy is a great alternative to Arduino if you want an ultra compact board with built in USB. The Teensy++ happens to also use the AT90USB1286, so it’s compatible with the SAV MKI. Follow PJRC’s instructions for installation from the download link.

If you only plan to program for RepRap, you don’t need to install any of the libraries. On Windows, you will be prompted to install the serial driver. Select yes . You don’t have to worry when Windows complains that the driver is unsigned… it’s just an INF file to tell Windows to use one of its own built-in drivers.

Step 3: Setup the SAV MKI on Arduino's IDE

Download SAV MkI: SAV_MkI.

Navigate to where your Arduino files are located. On my computer (a Mac), I have them in Applications\Arduino. I will call this from now on <arduinofolder>. Now, find the subfolder where the Teensyduino library was installed:


or (on a Mac)


If you are in the correct folder, you should already see a boards.txt and a subfolder called core in there. Drop the files from SAV_MkI into that folder, overwriting the existing boards.txt.

If you don’t plan to develop with any of PJRC’s Teensy or Teensy++ boards, you can keep them from showing up in your Arduino menu by copying boards.nopjrc.txt over boards.txt.

Now, when you start Arduino, you should see some new configurations in the Tools->Board menu. The important ones are:


Select SAV-MkI_RevD.1 for SAV MkI RevD.1.

Select SAV-MkI_RevD for all SAV MkI till RevD.

To use a USBtinyISP programmer, select either [usbtinyisp]AT90USB1286 or [usbtinyisp]SAV-MkI.

At this point, you can plug in your USBtinyISP and into your AT90USB1286/SAV-MkI and start programming!

So what are the [BootloaderCDC] configurations for? They allow you to download sketches into your target board directly through a USB connection to your host, without the USBtinyISP programmer.

To use the CDC bootloader, you would just need to set the board in bootloader mode (see below) and program the board through the USB using the arduino IDE.

Downloading the firmware with Arduino IDE

SAV MkI with PRG jumper (remove to program) and RESET button
SAV with PRG jumper (remove to program) and RESET button

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 SAV MkI called "PRG". Firmware can only be loaded while the chip has booted into its bootloader.

Download the pre-configured version of Marlin for the SAV MkI and open it in in the Arduino IDE. Use the released versions which have been tested, the main branch at times may contain experimental code.

To get into bootloader mode and upload new firmware:

  1. Remove the PRG jumper
  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. On Windows only, the first time you connect the board it will install the USB driver (note the new COM port number).
  3. Proceed to upload new firmware using the method relevant to your installed bootloader.
    1. CDC BOOTLOADER (Arduino Bootloader)
      1. In Arduino 105, open firmware
      2. Choose [BootloaderCDC]SAV-MkI (RevD o RevD.1) from the Arduino Tools-->Board menu, and select the COM port associated with your SAV MkI bootloader.
      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. Replace the PRG jumper onto the board
      6. Press Reset. You may need to disconnect and reconnect the USB and power cables.


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 or 1.0 with modified Teensylu boards configuration.

Installing A Bootloader


  1. Obtain a compiled CDC bootloader See also Lincomatic's Bootloaders for AT90USB1286 article where you can get the pre-compiled version of the CDC bootloader too.
  2. Connect the 6 pin programming cable to the SAV MkI ICSP header.
  3. Connect your programmer's USB cable.
  4. 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:0x5E:m -U hfuse:w:0xD3:m -U efuse:w:0xF0:m
avrdude -c usbtiny -p at90usb1286 -U flash:w:BootloaderNAME_HERE.hex:i
  1. Press Reset again.

WARNING: Triple check the fuse values! Setting incorrect values will brick the microcontroller! Fuse values above are for the CDC bootloader.

WARNING: These fuse settings disallow JTAG, in order to use those pins for a display. If you want to enable JTAG, hfuse value should be 0x93.

Using Atmel Studio 6

You can also upload the bootloader using Atmel Studio 6.

Simply select the AT90USB1286 processor as your target and open the board programming window. Flash the bootloader and then program the fuses:

low fuses: 0x5E
high fuses: 0xD3
extended fuses: 0xF0

WARNING: Triple check the fuse values! Setting incorrect values will brick the microcontroller!

How to wire your SAV MkI

SAV MkI Connection diagram.png

Step by step connection of the SAV MkI video (in Spanish): SAV MkI first time setup

In the video the hotend and heatbed are interchanged. Always follow the indications on your board's serigraphy.

REMARK: follow the wiring diagram in this page (the video has a few typos). The board's serigraphy always prevails to whatever is published on this page.

You can connect an inductive sensor directly to the SAV MkI RevD without the need of external componentes as indicated in the connection diagram above. The inductive sensor is connected to the auxiliary end-stop connector marked on the board's serigraphy as Z-12V. Make sure that you follow the wiring instructions for your particular sensor and connect V+ to 12V, GND or 0V to the GND pin of the connector and "signal" to the Sig pin on the end-stop pin of the board. In the wiring schematic above, you can see the most common color coding for the inductive sensor. However, ensure that you get the right polarity before connecting it to the board.

To get the inductive sensor working as the Z axis end-stop, you will need to modify the pin configuration on Marlin.

Change the file pins_SAV_MKI.h in Marlin as follows:

// #define Z_STOP_PIN         15
#define Z_STOP_PIN         36  // For inductive sensor.

Where to get one

If you missed the crowd funding campaign you can always get one from here, there are a few links to people that have them in stock:

Source files

Rev E - not produced


Rev B

SAV MkI RevB.png

Rev E

SAV MkI RevE.jpg
SAV MkI RevE render.jpg


The story behind the SAV MkI: The making of...

External links

Crowdfunding campaign: Indiegogo

electroFUN electrofun LTD

SAV MkI shootout: SAV MkI vs Sanguinololu shootout

SAV MkI box with integrated fan SAV MkI enclosure

SAV Mk1 holder for the M Prime One


The author would like to thank all these supporters and collaborators for making this project possible and backing it up during during the early stages of its crowdfunding campaign:

Clone Wars RepRap community, RepRap Zaragoza, Lluís Vilarrubies, Jose Antonio Perez , Pascual Alagon, Carlos Garcia, Javier Pajares, Jose M. Martin, Francisco Javier Sánchez, Antonio Javier Lopez, Manuel Palacios, Juan Manuel Amuedo - (oLE -, Adri, Chema Muñoz, Luis Macías, Ignacio Giniunas, Santiago Lopez, Valentín Cancelas, Antonio Javier Lucas, Clínica Veterinaria Noso Can, Arturo Pueyo, Shuttl3D, jgalaron, Ark, Fib and jgalaron.

The author would like to give a special thanks to these project supporters:

Andrew, ghosthawk


Proyecto Clone Wars