Arduino Graphics Card

Advanced graphics for anything from homebrew computers to weather reporting boxes and everything that can communicate over 3.3-5v UART.

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I have had this graphics card I made and was using for another project. The other project was being documented, but I realized that this card deserved documentation and a project of its own. It uses a Parallax Propeller to output VGA and NTSC video. It can be interfaced with 115200 baud UART. Now with a datasheet!

The NGT20 was originally designed to be a terminal for my custom computers. It executes this task amazingly well. With the default color configuration there are 3 foreground colors: white, red, and green. Red is great for STDERR or other error output. White for normal text, and green for anything you want to stand out. It automatically scrolls the screen when the cursor needs space to go down, making programming even easier.

How did you come to make this project???

Well I love to build computers. So I tried to make a single board computer with a parallax propeller.... and it never worked. The pcb was kinda scrapped and the project abandoned. Later, again working on an FPGA computer, I didn't want to make the FPGA do graphics, so I thought "Hey, why not use that old, scrapped and otherwise useless board to generate graphics?" Now, the remains of an old single board computer became my first version of this project! I never knew I could love a design so much, and I made another graphics card. A cleaner version. Now I am making them using boards from OSH Park! All thanks to a scrapped single board computer.

Where is the project now?

Pretty much got everything working. Will still improve it more sometime, so its still an ongoing project.

Quick specs:

  • Supports 3.3v and 5v UART
  • supports NTSC and VGA video output
  • Support for sprite rendering
  • RAM on card can be modified for quick, repeated draws of complex objects
  • Can be an arduino shield
To come once updated:
  • Higher Resolution (Maybe 640x480 VGA?)
  • More colors
  • Faster serial interface
  • Any suggestions?

My latest version is the NGT20, an advanced and refined product with all the latest bells and whistles.

Now available on Tindie here!


It's best to see the Documentation Portal instead.

Arduino Library:


Firmware Source Code:



NGT20 Datasheet

NGT15 Datasheet (WIP) (Outdated design! Why is this here?)

Please help me improve my datasheets! I would greatly appreciate feedback on these documents.

kicad_pcb - 147.70 kB - 04/24/2017 at 05:39


sch - 23.16 kB - 04/24/2017 at 05:39



A cool test program for an NGT15 or NGT20. Not compatible with GFXCard.spin firmware ;(

ino - 4.24 kB - 04/01/2017 at 03:12


  • 1 × Parallax Propeller GPU
  • 1 × 5Mhz crystal
  • 1 × 24LC256 Memory ICs / EEPROMs
  • 1 × 1.1k resistor
  • 1 × 560 Ohm resistor

View all 9 components

  • NGT30 Orderded from OSH :D

    Dylan Brophy2 days ago 0 comments

    I have ordered the prototype NGT30s from OSH.  I decided not to modify the board (like make any Through-hole components SMD or anything) because I am terrible at SMD resistor sizes and couldn't figure it out.  Should get the boards in a few weeks :D

    The new firmware will be pretty much the same as NGT20 firmware.  The board is just improved for flexibility and an added PS2 port, shrunken down and made more affordable.  I want to add something fun to the firmware but I have no idea what.  The current NGT30s have no NTSC/PAL port, so much of the RAM is not used and many cogs of the Propeller could be used.  If you have any thoughts let me know!

  • The NGT30 (And what color should it be?)

    Dylan Brophy02/13/2018 at 03:48 5 comments

    I finally decided how I want to make the NGT30.  After some first experiences with reflow soldering SMD, I have learned my limits.

    Unfortunately, using FPGAs is unrealistic.  It will take too long to come up with the VHDL, the chips are too expensive, and I will end up breaking half my boards due to soldering issues.

    Fortunately, I have the propeller chip in SMD form, which I can solder!

    I already have made a prototype board design in KiCad:

    I know I can both build and program this.

    The new design has numerous improvements over the NGT20.  Now,  RX/TX pins can be selected between a few different Arduino pins, thus increasing compatibility.  There is now a reset button for the arduino too, to make it easier to reach the Arduino reset.  I also added a PS/2 keyboard port, so now I don't have to keep cutting up keyboard cables :P.  The board is also smaller and cheaper as a bonus.

    I will be ordering this board *soon*.  I plan to add I2C support to speed up the connection, but I have reason to believe that the MCUs are the bottleneck for the NGT20, so we will see how much that helps.  Alternatively, the arduino would be able to use the hardware serial for the NGT20, parhaps allowing 1 Mbit/s connection to the NGT30.

    We will see how this goes in maybe a month XD

    Oh yea, what color should the board be?

  • The NGT30 - What will it be?

    Dylan Brophy08/15/2017 at 00:54 4 comments

    I would like to make an NGT30.  A few features I plan to add are follows:

    • Faster serial interface
    • Mostly SMD components
    • on-board arduino reset button for mega and similar boards
    • More commands
    • A way to add mods to firmware/GPU if I use an FPGA

    I may even remove the Parallax Propeller and replace it with an FPGA.  FPGA, not CPLD, because I would do some really killer stuff with it that may require an FPGA.

    I would like to make it backwards-compatible with my NGT20, so the serial interface must consider this.  I am mostly thinking about SPI, maybe I2C.  I would probably have some command to enable the new serial interface.  I would probably forget backwards compatibility if I used an FPGA however.  That would solve every problem :P

    I want to use SMD so that the board size is smaller, the BOM is less, and the parts cost less for the same quality.   This way the overall production price is reduced.

    I want to add the arduino reset button simply because it is really hard to reset my arduino mega with so many shields.

    Finally, I would like any suggestions.  If you're considering getting some kind of video shield or nice display output (or already have one), what would make things better?

  • Parallel Interface - with an upgrade

    Dylan Brophy07/04/2017 at 14:47 0 comments

    The propeller is a great chip, it is simple once you get used to it and works very well for simple applications, but its video output could be better:

    • Only 4 colors per area (exactly like NES graphics), only 6 bit color selections
    • VGA resolution capped at NTSC resolution because of memory limitations
    • Hard to get parallel interface

    The solution? An FPGA.

    This isn't the first time I have tried to make graphics devices using FPGAs and a parallel interface. Earlier on my #Z80 overpowered compute (possibly before I discovered HaD) I was trying to make... well a Z80 computer, but I overlooked some things and learned some hard lessons. So I had to literally start over. Well anyways I made a semi-nice graphics card designed to interface with the Z80 that also has a VGA connector and 8-bit DAC. It features a Mercury Board that stacks into a makeshift DIP64 socket.

    Here is this old board:

    I will improve it next time, promise!

    And some weird test program I was trying to write for it I found:

    Here is the bit configuration of the DAC:

    0 red 0

    1 red 1

    2 grn 0

    3 grn 1

    4 blu 0

    5 blu 1

    6 brightness 0

    7 brightness 1

    This will be a better design than before.

  • Parallel interface

    Dylan Brophy06/28/2017 at 03:23 0 comments

    Right now, the Open Source Graphics Card project supports only uart-capable devices. What about easy parallel interface for processors? Wouldn't it be nice to connect it to a Z80, 6502, or 8080? I think that will happen. The only thing I need is a circuit. Here is my current idea:

    My idea for a name is 'NGP10', as it is the first version and the middle P for parallel.

    I still am yet to get ESP support on my NGT20 design. I have an FTDI cable on the way for my ESP, don't worry. Keep you posted!

  • Yippie! Intel Curie (Semi) compatibility

    Dylan Brophy06/23/2017 at 04:47 0 comments

    Using a kinda lame hack I got it working. At first I used a hardware serial and put wires from pin 0 to pin 9 and pin 1 to pin 6. This unfortunately wastes 2 pins, but works as a shield. Next I tried using 4 wires to connect to the pins on the side, which also works and doesn't waste a pin, but then its not an arduino shield. Here is a pic of the first option:

    Sorry for bad pic - my phone has a terrible camera. Well I basically used some macros in the library to allow only AVRs and the Arduino DUE to use pins 6 and 9 for a softwareserial, and the others use Serial1. If they don't have Serial1... Well that's what I will have to figure out also.

    This probably works great for ESPs, but I can't test it on them! My ESP can't be programmed without a special FTDI cable that I don't have! Great win though, very encouraging. Oh yea, here is the first set of beefy macros I ever made, the ones for the NMT_GFX arduino library:

  • "Is it IoT Compatible?" - Someone

    Dylan Brophy06/22/2017 at 05:05 0 comments

    Well.... I never thought about that! It should be, after all it is 3.3v compatible, and what IoT MCU hasn't a UART? Of course the NGT20 is compatible! But what about the library? That's... Different. The Library for the NGT20 was built for and tested on AVR, however many IoT platforms use non-AVR MCUs, like the ESP8266 and Intel Curie. It is crucial for the library to have compatibility with these other MCUs so that nobody runs into trouble if they buy an NGT20 and realize there are software problems. I actually finally sold an NGT20 today (Yipee!), actually the only 2 I had in stock, and so now that I am selling them it is ever more important. This possible compatibility issue was brought to my attention when I was asked about NGT20/ESP compatibility.

    I put in an order from @SparkFun Electronics that arrived today including an ESP8266 and Arduino 101, which is Intel Curie based. I will be developing my library with my new test hardware (I never used an ESP or Intel Curie before!). I know that those ESPs are a learning curve, and can be SUPER difficult to use.

    So far I cannot program my ESP Thing because I got one that needs an EXTERNAL FTDI Serial bridge (Dang it!), and my first test on my Intel Curie is unsuccessful. Will keep things posted.

  • Non-AVR library compatibility?

    Dylan Brophy06/18/2017 at 20:34 0 comments

    The NGT20 works for almost any device if you have the right software. The library, however, was not originally designed to work on non-AVR MCUs. This is one thing in the design process back in spring I never thought about because I don't use the Arduino IDE for anything else. Well, recently I was asked a question regarding the library's support of ESPs. I don't actually own an ESP, so I borrowed one from my friend. The ESP itself has so many problems and keeps rebooting, I can't even test my library! I thought I might as well get my own ESP, but what about other MCUs that are programmed from the Arduino IDE, but aren't AVRs? To begin testing that I ordered two dev boards from @SparkFun Electronics, their ESP8266 Thing and an Arduino 101. Since I really need the library compatible sooner rather than later I got 2 day shipping, so I should hopefully have an updated library by the end of the week.

  • Integration into my computer building obsession

    Dylan Brophy04/09/2017 at 05:44 1 comment

    If you've read my profile much you will see that I really, really like to make computers. For no apparent reason. I have done (or at least attempted) in many ways, like building a z80 computer, or trying to make CPUs out of CMOS ICs, or using an arduino yun + a screen + a keyboard. Well, a wile back I made this really cool system with an arduino. It even did some multitasking. Two things really sucked about it: its display output and the user input. For user input it had 2 buttons and a potentiometer. It used a 2x16 character LCD screen. It was really cool, but I found the code recently and decided "Why not add a keyboard and an NGT20?" I needed some videos showing my NGT20 anyways, so I have been porting most of it to the new design. I added a GUI and a nicer shell program. No file system yet, but the beginnings of the OS and all the programs are emerging. Here is the video.

    This is how far I've gotten. I want to make a Terraria like game on the arduino using my NGT20. It probably wouldn't be as complex as Terarria itself, but similar idea. So cool because I always want to play Terraria but I never want to actually pay for the game.

  • Arduino library fixes, finished datasheet, and TINDIE!

    Dylan Brophy04/05/2017 at 00:30 0 comments

    I've been wanting to post this project on Tindie for a while so I've been working hard on the documentation and Arduino library. Now that that stuff's done, I can focus on selling. I'm working on the description and more pictures and such. So yea, tomorrow you'll be able to order one for yourself! Im really excited because I always want to grow my money, I want to be an entrepreneur, and I never want to spend anything on a project. Maybe this will be the avanue to extra cash for everything I love to make. Anyways, I'll be posting a link to my Tindie store soon. In the meantime, I have these much better photos that are fit for an online store:

    Hope this works!

View all 13 project logs

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Vishnu M Aiea wrote 02/13/2018 at 11:03 point

Brilliant! You should give this to high end graphics card enthusiasts and tell them to have a good look at it. May be you could show it to Linus and have it reviewed. I must warn you; he'll probably drop it..

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ɖҿϝիɟթվ wrote 02/13/2018 at 13:22 point

Why Linus? What does he have to do with this?

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Vishnu M Aiea wrote 02/13/2018 at 13:28 point

Linus Sebastian - from Linus Tech Tips, not Linus Torvalds :D

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ɖҿϝիɟթվ wrote 02/13/2018 at 13:31 point


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Mark Sherman wrote 03/27/2017 at 21:16 point

I would like to see this with a SPI bus. A lowly Arduino can output SPI with a few Mhz SCLK, beats out 115kbps pretty well.

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Dylan Brophy wrote 03/28/2017 at 01:27 point

I would love to add a faster serial interface. the only issue is the boards I have only 2 connections between the arduino and propeller. If you have any other fast serial protocol ideas i would love to hear, and I myself will think and look into this. Thankyou :D

P.S. - creating a project to solve this. bidirectional pins is out of the question for my OSH park boards ;( but im sure I can still make a custom high speed serial protocol. #2-pin SuperSerial

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Steven Gann wrote 10/19/2016 at 22:56 point

Lovely. I can't wait to mess around with it this weekend.

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Dylan Brophy wrote 10/28/2016 at 00:11 point

How'd it go?

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Steven Gann wrote 10/03/2016 at 11:52 point

I've been working on a homebrew CPU and am looking for a graphics adapter. The last Parallax product I used was the Basic Stamp II, back when the BoE used RS-232, so I don't know a lot about Propeller. I do happen to have a Propeller Demo F board in my collection, but never used it.

Definitely excited for more information on this.

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Dylan Brophy wrote 10/05/2016 at 02:06 point

Il make a schematic of the board I made and upload it.  If your making your own cpu, are you using an FPGA or discreet logic, or something else?  If your cpu is 5v or needs UART support you may need a few chips, but with a Demo Board you will have a great graphics adapter. I would recommend it.

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Steven Gann wrote 10/05/2016 at 19:22 point

Right now, all I have is an emulator ( I picked up a Max II CPLD to learn VHDL, because I've been wanting to get involved with FPGAs anyway.

A schematic would be helpful, thank you. It seems the Prop is popular as a video adapter.

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Dylan Brophy wrote 10/18/2016 at 13:21 point

Ok I have made a schemtic and it is in the source code.  If you open the GFXcard.spin in the Propeller Tool, you will see the code and the documentation.

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Dylan Brophy wrote 03/26/2017 at 16:24 point

Hey, haven't heard from you in a while. How has it come?

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