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Papilio DUO - Drag and Drop FPGA Circuit Lab for Makers's video poster

Simply draw circuits connected to an Arduino-Compatible chip. Supercharge your sketches and unleash your inner DaVinci! Read more

Westminster, CO Hardware
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This project was successfully funded on June 27, 2014.

Simply draw circuits connected to an Arduino-Compatible chip. Supercharge your sketches and unleash your inner DaVinci!

Westminster, CO Hardware
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About this project

Thank you for visiting the Papilio DUO Kickstarter page. Sadly the Kickstarter has ended, but don't worry the Kickstarter was a success and boards will be available soon! Visit the Papilio DUO information page to catch up with the latest news and get a Papilio DUO of your own.

We live in exciting times where we can create masterpieces with the Arduino and marvels with the Raspberry Pi. Where we can use technology as a canvas to create things that amaze and amuse our friends and family. Wouldn't it be great if we could take the same technology that has been the staple of rocket scientists and put it in our creative arsenal? Without the need to become a rocket scientist or the headache of learning a new programming language like VHDL/Verilog.

Why can't we just draw up the circuits that we want to use? With the right software and circuit libraries we can! Let's put a full circuit lab on a chip, pair it with an easy to use Arduino-Compatible chip, and sprinkle in a generous helping of debugging tools. 

FPGA and Arduino-Compatible Chip Together at Last

The Papilio DUO has an FPGA on the top and the same chip that is used in the Arduino Leonardo (ATmega32U4) on the bottom. It's like having an Arduino with a full circuit laboratory connected to it! For example, you can draw circuits to move pins, connect extra serial ports, or connect a bitcoin miner to the Arduino-Compatible chip. Just plug it into your computer using a USB cable, download our software and start drawing your own circuits.

FPGA Unleashed!

Our dream is to take the hardcore out of FPGA (Field Programmable Gate Array) and make it an amazing tool that anyone can use for creative technology projects. 

Just like the Arduino team simplified C++ programming, we simplify FPGA design by providing easy to use drag and drop circuit libraries. We believe that drawing circuits will result in an amazing outpouring of creative FPGA projects!

Use the Papilio DUO to unleash your inner DaVinci. Draw and debug circuits on a chip without any soldering, breadboarding, or weird programming languages. Set your imagination free and put an FPGA in your creative arsenal!

Software and Features

The Papilio DUO is much more then just a hardware project. In fact, the software is the secret sauce that sets the DUO apart from other FPGA boards. It lets you draw up circuits without investing time and energy in learning VHDL/Verilog.

We start with the Arduino IDE (Integrated Development Environment) and supercharge it by adding circuits into the mix. We bring all of the pieces needed to draw and debug your very own circuits in one place. It's an easy and seamless user experience that we call Papilio DesignLab for use with both Windows and Linux.

Papilio DesignLab

We start with the Arduino IDE but every sketch now has a circuit associated with it - editing and debugging circuits is just a click away!

Every Sketch has a Circuit with it!
Every Sketch has a Circuit with it!

Simply draw and debug your circuits!

Click on the "Edit Circuit" button and simply draw your circuits using the Xilinx ISE schematic editor and our Papilio Circuit Library.

Simply Draw Your Circuits with DesignLab! No VHDL/Verilog to learn!
Simply Draw Your Circuits with DesignLab! No VHDL/Verilog to learn!

Logic Analyzer

Drop a professional quality Logic Analyzer into any circuit and know instantly what it's doing. Up to 32 channels and 200Mhz speed handles any circuit you can throw at it. Use up to 75KB of internal memory or the external SRAM memory.

Wire in a Logic Analyzer without disrupting the existing circuits!
Wire in a Logic Analyzer without disrupting the existing circuits!

System on Chip - Draw Soft Processor Circuits!

Want to get into more complex circuits? DesignLab includes the ZPUino Soft Processor with a Wishbone bus, providing greater speed and flexibility than the Arduino-Compatible chip. A Soft Processor runs inside the FPGA and uses the Wishbone bus to make it easy to connect peripheral circuits, such as UARTs, PWMs or SPI masters. Making your own Soft Processor with just the right mix of peripheral circuits is known as a SOC (System On Chip) design. With DesignLab you can draw your SOC designs in minutes! 

Create SOCs with ten serial ports, or a PWM on every pin, or something exotic like classic Atari and Commodore audio chips connected at the same time. The sky is the limit, you can create things that don't exist anywhere else!

Example of making your own SOC design with ZPUino and a Commodore 64 SID audio chip. (This tutorial was written for an earlier version of our software. DesignLab integrates circuits and sketches together for a much easier and seamless user experience.)

(Take a look at the full tutorial on our learn website and see what all the Papilio DUO tutorials will look like.)

Papilio Circuit Library

Drawing circuits can only accomplish so much without a library of circuits (known as cores) to do the heavy lifting. Our goal is to provide the framework for anyone to write a core that can be wired into a circuit.

We want to seek out the best open source circuits on the interwebs and convert them to a dead simple schematic library. The internet is absolutely full of open source circuits; just take a look at sites like You will find everything from classic audio chips to stepper motor controllers. All of these amazing circuits are within our reach when converted to schematic form!

Take a look at what is already available in the beta version of DesignLab. (Cores colored in red are still in progress.)


The Papilio DUO is a third generation Papilio board. As such, it benefits from all of the tricks we've learned along the way as well as extensive feedback from the community. This past experience and community feedback drove the development of this board and puts the users needs first.

Extensible - The first thing that people always ask for is the ability to use their Arduino shields. We listened and started with an Arduino-Compatible footprint, retained support for six Papilio Wings, and even squeezed in support for one PMOD connector! Adding new hardware to your FPGA has never been easier, there is a huge selection of hardware out there just waiting for you to discover.

Add a Shield and Five Wings - No Need to Stack Shields...
Add a Shield and Five Wings - No Need to Stack Shields...


Six Wings - No pin conflicts, each pin is dedicated, just draw a circuit with what you want connected to it! UART, SPI, PWM, whatever...
Six Wings - No pin conflicts, each pin is dedicated, just draw a circuit with what you want connected to it! UART, SPI, PWM, whatever...

SRAM - Easy to use SRAM is a must. We've used SDRAM in the past and it was a big mistake! The strict timing requirements and interfacing caused fits for everyone. SRAM is asynchronous and dead easy to use, you will greatly appreciate the simplicity of SRAM in your projects. 

Tremendous value: We are working to make a brand new creative tool for technologists - so the hardware has to be something special. Just look at the tremendous value that has been packed into this board, if you bought all of this functionality separately it would cost over $500! The Papilio DUO does all of this for just $88!

Hardware Specifications

's video poster
Papilio DUO - Callouts
  • A) Spartan 6 LX9 FPGA (Datasheet)
  • B) High efficiency LTC3419 Switching Voltage Regulator (Datasheet)
  • C) Dual Channel FTDI FT2232H USB 2.0 Interface (Datasheet)
  • D) 512KB or 2MB ISSI IS61WV5128 SRAM (Datasheet)
  • E) 64Mbit Macronix MX25L6445 SPI Flash (Datasheet)
  • F) Atmel AVR ATmega32U4 - Arduino-Compatible Chip (Datasheet)
  • G) 54 I/O pins arranged in an Arduino-Compatible Mega Form Factor
  • H) Digital Pins 0-16 Connected to FPGA and ATmega32U4

Papilio DUO Images

Papilio DUO Front - FPGA Side
Papilio DUO Front - FPGA Side


Papilio DUO Back - Arduino Leonardo Compatible Side
Papilio DUO Back - Arduino Leonardo Compatible Side


Bonus Functionality

Full Debugger for the ATmega32U4

HappyJtag2 is software that emulates an Atmel JTAG ICE MKII debugger. It requires that the FT2232 USB chip be connected to the Arduino-Compatible chip in a special configuration. The unique ability of the Papilio DUO to implement any circuit allows us to make this special connection with ease. The creator of the HappyJtag2 software was kind enough to work with us on our prototype hardware and added support for the ATmega32U4 chip. The end result is that we can get full debugging support for sketches by simply loading the correct circuit. With debugging we can load hex files, set fuses, step through code, modify variables, view memory space, everything you would expect from an official MKII debugging board! (The only downside is the HappyJTAG2 and AVR Studio software only works in Windows, sorry Linux users.)

Classic Computing Shield

As a bonus for this Kickstarter we are offering a Classic Computing Shield which will provide all of the hardware needed to recreate classic computing systems on the Papilio DUO. Here are some existing retro computing projects that can be easily converted:

Classic Computing Shield V1.0
Classic Computing Shield V1.0
  • 4096 Color VGA
  • Audio Jack
  • Two PS/2 Jacks
  • Two Atari Style Joystick Ports
  • MicroSD Socket
  • Directional Control Buttons
Wing Pack
Add a collection of our most popular and useful Wings to the Papilio DUO. A $60 value for just $39.99!


RGB LED Panel Demo 

Alvaro put together this nice demo to show what is possible with the Papilio DUO. Visit the update for more information.

Someone asked, "Can you play video on the panels?". So Alvaro whipped up a quick demo of doing just that! Read more in the update.


Why Pledge Now?

  • We Need Your Help - It has taken everything we have to get to this point and all resources are now exhausted. Without your help and the funding from a successful Kickstarter the Papilio DUO will die on the vine...
  • Exclusive Kickstarter Edition - The first batch of Kickstarter Papilio DUO boards will have a special feature that will make them unique. We will present several ideas, such as a unique color scheme or silkscreen artwork, that you will be able to vote and collaborate on. Only Kickstarter backers will get in on this special edition.
  • Be a Collaborator - We treat backers as collaborators - your input and ideas are valued. We make all decisions regarding the Papilio DUO and stretch goals after asking for your input.
  • Prototype Boards - We intend to build 5-10 prototype boards to put into the hands of a few backers as early as possible. If you have a killer idea that just can't wait then, as a backer, you can plead your case for one of the early prototype boards. Only backers will be considered for the prototype boards and at least one will go to a randomly selected backer.
  • Be a Part of a Dream - The Papilio DUO could be the next creative tool on Makers desks around the world, right next to the Arduino and Raspberry Pi, and you can say you made that happen!

How the Papilio DUO Came About

Back Story - One of the challenges of using the Arduino-Compatible footprint is the analog inputs. FPGA's have no analog inputs so we need an external means of including analog. While chatting with Mark Cooper (of Smoothieboard fame) he recommended using a cheap AVR chip. I thought that was a great idea, but as I thought about it more it hit me like a ton of bricks! If I'm going to add an AVR chip, why not go all the way and use the chip from the Arduino Leonardo! We would then have an Arduino-Compatible chip and FPGA together for the first time. The FPGA can act as a circuit lab for the Arduino-Compatible chip!

I quickly downloaded the Arduino Leonardo design and flipped it upside down onto the bottom of a circuit board. I placed the FPGA design on the top and quickly hit a brick wall. There was no way to route both designs on a two layer board... I expanded to a four layer board and with careful hand routing and re-ordering of the pins everything came together and the Papilio DUO was born.

Stretch Goals

Stretch goals will allow us to give something back to the Open Source community and bring in the help of some talented developers who have helped us in the past. 

Surprise Stretch Goal! Free RGB LED Panel Wing if we reach $75K!

We are coming down to the last few days of the Kickstarter campaign and after being inspired by the awesome RGB LED Panel Demos that Alvaro made I decided to make a special stretch goal to end with a bang. :) If we can reach $75K in funding then everyone who backed us for an assembled Papilio DUO will get a free RGB LED Panel Wing. Visit the update to learn more and see how you can help reach $75K!

Arduino-Compatible chip to Wishbone bridge - Alvaro Lopes - $40K

Achieving $40K of funding will allow us to enlist the help of the amazing Alvaro Lopes to create a high speed bridge between the Arduino-Compatible chip and Wishbone cores running on the FPGA. This will most likely be SPI based and run around 20Mhz... Alvaro is a rock star when it comes to these types of projects and it will be a real win for the community if he can work on this important functionality. 

Case for Papilio DUO - Os1r1s - $50K

A Papilio user called Os1r1s made an amazingly elegant case for the Papilio Pro. If we reach this funding level we will enlist the help of Os1r1s to make an equally amazing case for the Papilio DUO. (To be sold separately.)

Hamster's free Learning VHDL eBook - Hamster - $60K

While we are going out of our way to ensure you don't have to learn VHDL, the Papilio DUO is still a great board to learn VHDL with if you are so inclined. In fact, Hamster wrote a great VHDL eBook for the Papilio One and the LogicStart MegaWing to help with just that thing. If we reach a funding level of $60K then we will work with Hamster to create an updated version of the LogicStart Shield for the Papilio DUO (to be sold separately) and he will update his eBook to cover the Papilio DUO!

Gameduino 1.0 - Alvaro Lopes - $70K

We already have the Gameduino 1.0 Verilog code converted to schematic form, but we lost steam when it came to converting the Gameduino libraries to the ZPUino. If we reach this level of funding then we will be able to enlist the help of the ZPUino creator, Alvaro Lopes, to convert the Gameduino libraries to the ZPUino. How cool will it be to use the Gameduino core for video and then drop in a Commodore 64 core for audio! Its never been done before and if we reach this stretch goal you can easily draw this SOC.

Stepper Motor Wing - Mark Cooper (Logxen - Smoothieboard) - $80K

Mark Cooper, of Smoothieboard fame, has agreed to make a stepper motor wing for the Papilio DUO if we reach this funding level (to be sold separately). The board will be perfect to make robots and autonomous vehicles with. Drag and drop the existing stepper motor core into a circuit and control this stepper motor wing without using any resources in your sketch!

Sound Puddle Mini Wing - John English - $90K

Sound Puddle is an amazing art project that drives over 10,000 RGB LED's to create an immersive and interactive space of visual-acoustic synesthesia. It is a great example of the type of project that a Papilio FPGA can handle with ease. With 10 SPI masters plugged into the ZPUino Soft Processor it is a custom System on Chip design never seen before. If we reach this stretch goal we will convert the Sound Puddle design to schematic form and work with John English to make a mini Sound Puddle Shield (to be sold separately).

HDMI Wing and Core to drive it. - Alvaro Lopes - $100K

We will create a special HDMI Wing for the Papilio DUO (to be sold separately). Alvaro Lopes, the creator of the ZPUino, will make a wishbone core that can be dropped into your circuit and a library to drive it from your sketches. Due to the limited SRAM memory on the Papilio DUO it will not be possible to achieve HD resolutions, but it will still be extremely useful. Old games like PacMan can be enjoyed on an HDMI monitor or television. User interfaces and displays at 480p resolutions should be possible from user sketches.

Open Source License

The Papilio DUO is completely Open Source and uses a OSHW approved Creative Commons Attribution-ShareAlike 4.0 International License

This means you can make a Papilio DUO for yourself or an army of Papilio DUO's for your hackerspace!

The Papilio DUO EAGLE files can be downloaded from our Github repository.


The bottom side of the Papilio DUO was derived from the Arduino Leonardo reference design which is licensed under the Creative Commons Attribution Share-Alike 2.5 license. The Arduino Leonardo design was modified and can no longer be considered an Arduino Leonardo. Instead the product is a combination of an FPGA and the Arduino derived design and is called the Papilio DUO. The Papilio DUO is not endorsed by Arduino nor is it an Arduino product. It is compatible with the Arduino software and we hope it plugs into and adds to the Arduino universe in a way that is useful and helpful. We are extremely grateful for the wonderful work that the Arduino team has done and the Arduino Leonardo reference design that made the Papilio DUO possible. Without the power of Open Source the Papilio DUO would not exist.

The Papilio DesignLab software is a fork of the Arduino software that has a different name and a different look and feel. It was necessary to create a new fork since the new circuit functionality we are adding is not compatible with existing Arduino boards. 

The music used in the video is called, "The Owl Named Orion" from and is licensed under a Creative Commons Attribution 3.0 United States License.


Previous projects successfully completed:

  • OpenBench Logic Sniffer with Ian Lesnet. I did the FPGA side of the OpenBench Logic Sniffer.
  • The existing line of Papilio FPGA boards.
  • The RetroCade Synth Kickstarter project.

Your support of this Kickstarter project will fund our development of this idea and bring about a powerful new tool for your creative energy.

Risks and challenges

The biggest risk for this project is not being funded... We are a very small team with a big idea to make FPGA design as easy as drag and drop. Without your backing and the resources to continue developing this idea it will die on the vine... So please help us Kickstart this idea and get it off the ground! We need your vote of confidence and financial backing to bring this idea to fruition, so please don't wait, back us today. :)

If the Kickstarter is a success then manufacturing is the next biggest challenge. Hardware can be a real challenge to get right. No matter how much you check and double check mistakes can slip through. Seeed Studio will be manufacturing the Papilio DUO and we have a process with them that works very well. It takes time to go through all the steps but it really goes a long way to ensure that a quality product is delivered. It's tempting to speed things up by skippping some of the steps or ordering boards directly from an assembly house without completing a test plan. Instead we ask for your patience as we take a little longer to go through the steps with Seeed Studio.

We are starting out with a working board that we feel very confident in. We have put it through a battery of tests that exposed some simple mistakes. Having the board in hand also exposes any problems with the silkscreen and component placement. We have fixed all the mistakes discovered in testing and tweaked the design through multiple revisions of the board. What he have now is the third revision of the board which is finally ready for the manufacturing stage.

We have already generated a Bill of Materials that we have submitted to Seeed and they have provided us with a price per unit that allows us to set the Kickstarter pricing with a sense of confidence that we won't find our selves in hot water from bad pricing.

After the Kickstarter completes we will start work on the next steps:

1) Build a manufacturing sample to send to Seeed Studio. They will have this sample on hand to refer to as they setup the assembly of the boards. If they have any questions about a part or how it should be placed on the board they will refer to the sample.
2) I will work on an automated test plan that can be quickly loaded to the board and will test all major functionality of the board. From USB communications, to SRAM, to testing for solder joints on the I/O pins. Example test plans for previous Papilio boards can be seen here.…
3) Seeed will run the test plan on the manufacturing sample I sent to them and make sure all works as expected for them.
3) Seeed will manufacture a test run of a couple boards using their sourced components and assembly house.
4) Seeed will run the test plan on their boards from the test run. If all goes well they will pass the automated test plan and we will have a high level of confidence to proceed with a full scale manufacturing run. If there are any problems we will try to troubleshoot over skype, and in the worst case scenario they will ship one of the test run boards to me for testing. If this happens it can take some time, so far it has only happened once, and it ended up being a single component that needed to be replaced. We want to catch this sort of thing before we manufacture hundreds of boards!
5) Seeed will do a large batch of boards to fulfill the needs of the Kickstarter project. They will then run the automated test plan on each and every board, package up the board, and mail them directly to you.

This process should take 3-8 months after the Kickstarter completes. If all goes smashingly well it is conceivable that boards could be in the hands of backers as early as two months after the campaign completes, but we will always take a cautious approach which can translate to taking more time...

The software is the other piece of the puzzle for this project. We already have a beta version of the software that does all of the things we talked about. For some things, like the Virtual Instruments, we put together code to prove that the idea was doable. We now need to clean up that code and make it solid and reliable. We expect to work full time on the DesignLab software and will provide constant beta releases as we go. We expect to release the first stable 1.0 release for Windows and Linux in six months after the Kickstarter completes.

Learn about accountability on Kickstarter


  • So the question, "What is the difference between stand alone and wishbone". Lets look at the YM2149 for this example. The YM2149 would be standalone if I created a core that had all of the original YM2149 pins and you had to manually connect up all of those pins to the Arduino on the FPGA. It's like when someone takes a physical YM2149 chip, puts it on a breadboard and then runs jumper wires from the YM2149 to the Arduino. A core setup like that would be a standalone core and would be setup to work just like the YM2149 chip. A Wishbone core is like if someone put a YM2149 chip on an ISA card and all you had to do was pop it into your computer case and then write to the I/O locations for that ISA slot to communicate with it. Much easier, you don't have to learn all the details of how to wire up the chip. You just need to know what ISA slot it is in...

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    Love the idea but not big into tinkering with electronics? No worries, back us at any level you want and get updates as things progress. The hardest part of any project is getting the word out, so supporting us at this level and helping to spread the word is greatly, greatly appreciated.

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    Love the idea of Open Source Hardware? Love that you can build this board for yourself, or build an army of them for your hackerspace? Get a 4-layer bare PCB (Printed Circuit Board), a bill of materials (you can order parts from Digikey), and answers to any of your questions so you can build yourself a Papilio DUO. You will get the bare PCB before anyone else so you can start building right away. (This reward is only meant for those looking for a souvenir or who are comfortable with surface mount soldering and want to order the parts and build the Papilio DUO themselves. No parts are included with this reward and the PCB is not assembled or operational.)

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    You helped out with feedback in the forums while the Papilio DUO was designed and know exactly when this project is going live! Thank you for your support and here is a special price for you. (Papilio DUO with 2MB SRAM) (Add $20 to include Classic Computing Shield) (Add $39.99 to include Wing Pack)

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    Here is a special price for those who believe in us enough to jump on board right away. Please tell your friends and help us spread the word about this project. (Papilio DUO with 512KB SRAM) (Add $25 to upgrade to 2MB of SRAM) (Add $24 to include Classic Computing Shield) (Add $39.99 to include Wing Pack)

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    PAPILIO DUO DELUXE BUNDLE Papilio DUO with 2MB SRAM. (Includes Classic Computing Shield) (Add $39.99 to include Wing Pack)

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    11 backers Limited (19 left of 30)

    The first 30 boards off the assembly line will be packed up and sent directly to me where I will personally number and sign the back of each board. Board number one will go to the first person to order on this tier, two will go to the second and so on. (Papilio DUO with 2MB SRAM) (Includes Classic Computing Shield) (Add $39.99 to include Wing Pack)

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    Love the idea and want to see it brought to fruition? Want your company to help bring this idea to life with a sponsorship? Get 10 Papilio DUO's and your corporate logo and a link to your website in the footer of every Papilio DUO web page, tutorial, and wiki page. (The Papilio DUO boards will include 2MB of SRAM) (Includes Classic Computing Shield)

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Funding period

- (30 days)