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The Devtendo!

Introduction | Adaptors

In early 2004 I whipped together a simple video capture device to take screen shots of the video from an original Game Boy, as well as understand how it worked. It progressed into a multipurpose device which was useable on other devices, including the Game King handheld. Though designed as a screen capture device, I realized that I could take the shots quite quickly, and thus, was actually able to display the screen shots as video on the PC.

Not long after building the Game King adaptor, I began designing a more powerful version of the capture device. However, with work and other projects, the idea was put on hold. However, at the end of 2004 with some of my time off, I designed and built the Video Capture Device 2!

The Video Capture Device 2 is a data sampler which, when clocked, stores an incoming stream into SRAM chips. The data on the RAM can then be read by a connected PC, and in the case of a video stream, displayed through it. The original version was simpler and only contained a single 32Kx8 bit SRAM. This new version can support up to 16Mx16bit, or 32MBytes of RAM. Of course, not nearly that much is needed, so I currently only have 256KBytes of SRAM in it. With this amount, it could support up to screens of 512x256x16, 320x400x16, 640x200x16, etc. Beefing it up to 512KB would allow 640x400x16 and so forth.

As well as supporting 16 bit video and large amounts of RAM, it also can support both negative and positive edge vertical sync and data clock pulses depending on how the attachment is jumped. In addition, it can run off the power from the device it's capturing video from, or if plugged in, it can power the device. This ensures proper capture without pull ups/pull downs on all of the input lines and such. It only needs pull downs on the four parallel port output lines, which greatly simplifies things.

Because it captures digital video, it can take perfect bit for bit screen shots. When viewed on a PC monitor, it looks excellent! Much better than when viewed on a regular TV.

This will likely conclude my screen shot video devices. Since the RAM is not dual port, it can only run at a maximum of half of the FPS, as it must wait one frame for the screen to be drawn before reading it each time. The next device I build will be done with either dual port RAM or some smart latch design, allowing for the full video to be captured at the full FPS. As well, I plan for it to work with or without a PC, allowing it to display to a monitor itself.

Adaptors

The Video Capture Device 2 is built to be very versatile, and I plan to eventually build adaptors for all of the handhelds which I have. Here are the devices which I have built adaptors for so far:

  • Game Boy (Pocket) Adaptor - A super simple adaptor which allows capturing of the original GB's 2 Bit video stream.
  • Game Boy Advance Adaptor - The ultimate! Thanks to the GBA's backwards compatibly, it supports viewing of Game Boy, Game Boy Color, and Game Boy Advance games
  • Tiger Game.com Adaptor - Finally the world can see what Game.com games look like on a real screen!


Document and Information By Brian Provinciano
January 2nd, 2005
Updated January 16th, 2005

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