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Wednesday, July 04, 2012

CGA2VGA scaler for arcade PCBs


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UPDATE (03/01/15) There have been a lot of breakthroughs in hacking these Gbones upscalers via Raspberry Pi and I2C connection.   Details can be found on the shmups forum thread located here.
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I made a very interesting discovery with the CGA2VGA scaler that came in my Red Storm cabinet.  The scaler looks like the generic/OEM version we've all seen on eBay for ~$35, except even cheaper since they removed all the components except for RGB input and VGA output.  But the big difference is the one that came in my cab can successfully scale PCBs of various refresh rates, like the very difficult Seibu 55hz games!

Here is a visual comparison.  The Gonbes GBS-8220 in on the left, and the Red Storm generic is on the right.

(click picture for hires pic)

Comparing both side by side in a similar setup, the menus are exactly the same, except the red storm version allowed for a wider range of values to be set for horizontal and vertical settings.  Looking closely at the both boards, the GBS-8220 has a 2011.08.16 V30 silkscreened on it, while the stickers on the red storm version looks like it's firmware was updated in February of 2012.

So I'm hoping someone can help me figure out how to dump the firmware of the red storm version and see if I can successfully upgrade the GBS-8220 firmware.  I see there are two sets of 4 pin "upgrade" connectors on the right side, although it looks like some were removed.  There is also a 2 pin connector directly under these which I assume may be a selectable "write" jumper?



10 comments:

  1. Thanks for the article.. Will def look for one with the newer firmware!

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  2. The top upgrade pins labled with SDA, VCC, GND, and SCL are I2C (Inter-Integrated Circuit protocol). Below the I2C port is either Serial or USB port.

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    1. Thanks beatsgo! I'll look into the I2C protocol to see if this is something I can easily wire up.

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  3. did you ever figure this out?

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    1. There are USB to SPI/I2C/IIC/UART/TTL/ISP serial adapters on eBay for cheap, but I have not yet bought one to try dumping the firmware. In reading up on IC2, it sounds like companies typically protect their firmware by making proprietary functions, so I kind of lost interest (and time) to try.

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  4. Does your red storm adaptor suffer from the de interlacing shimmer that the normal GBS-8220 suffers from?

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    1. I use the adatper to upscan PCBs from 240p to 480p, so there is no de-interlacing involved. However, I do see some video artifacts which could look like shimmer in certain crosshatch textures, from upscanning the progressive signal similar to the GBS-8220, so I think the answer to your question it, yes.

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  5. Don't bother trying to dump the firmware it will definitely be protected.
    There is a more expensive converter made by the same company called a "XVGA Box". This can handle all frequencies and has no video or shimmer issues like the cheaper version.

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    1. Thanks the advice Guru! I'll checkout the XVGA Box (GBS-8219).

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