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Open Source Graphics Card

Simple graphics for homebrew computers, arduino projects, or anything 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 NTSC video. It can be interfaced with over 115200 baud UART. Will be working on documentation soon.

What if my project doesn't support UART?
I would use a chip like a 16550 UART chip or another microcontroller to interface.

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.

Quick specs:

  • Supports 3.3v and 5v UART
  • supports NTSC video output
  • Can be an arduino shield
To come once updated:
  • Support for VGA output
  • Support for sprite rendering
  • RAM on card can be modified for quick, repeated draws of complex objects
  • More and more rendering functions...
  • Dual monitor support???

My latest version is the NGT15, a prototype that is a bit more sturdy, has better rendering functions, and supports 5v UART.

Datasheets:

NGT15 Datasheet (WIP)

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

firmware_1.0.spin

Some newer firmware

spin - 19.52 kB - 03/21/2017 at 03:21

Download

GFXCard.spin

Firmware for the graphics card

- 19.38 kB - 10/05/2016 at 03:21

Download

View all 2 files

  • 1 × Parallax Propeller GPU
  • 1 × 5Mhz crystal
  • 1 × 24LC256 Memory ICs / EEPROMs
  • 1 × 1.1k resistor
  • 1 × 560 Ohm resistor
  • 1 × 270 Ohm resistor
  • 1 × RCA (Phono) jack
  • 1 × PCB If you want a really nice one, order from OSH Park
  • 1 × 74lvc245 Only if you want 5v UART support

  • Improvements : Prototype made on OSH park board!

    Dylan Brophy03/20/2017 at 23:27 0 comments

    I made a schematic for a new graphics card with KiCad, and ordered my prototype on OSH Park! The boards came in last friday and I have since started creating new firmware. The new prototype comes with a 74lvc245 to allow communication with 5v devices. The new card also fits on the arduino, however it makes it a bit difficult to program, but it's still really cool! It would also support VGA output however I goofed up the schematic.

    In short, my new design is awesome and arduino - compatible.

    I also made a new schematic yesterday with the VGA and some other problems fixed, and ordered those boards. I will upload some pictures later today.

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Discussions

Mark Sherman wrote 3 days ago 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 2 days ago 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.

  Are you sure? yes | no

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 (https://github.com/stevengann/sg16). 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 4 days ago point

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

  Are you sure? yes | no

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