RGB2VGA with GBS8200

GBS8200 board. Hacks and Improvements

GBS 8200 is a cheap RGB to VGA converter board. However, some improvements are necessary to obtain a reasonable quality.

Connecting a retro computer such as MSX to an VGA monitor is a nice thing, as they can be found for a small fee and occupy less space than CRTs. However, converting the output from a retro computer to a standard VGA monitor is not straightforward due to different scan rates. GBS8200 is a nice and cheap board to upconvert the 15KHz frequency to the 31KHz VGA scan rate making an effective conversion from RBG to VGA.

Unfortunately, the image quality is not very good as GBS8200 comes from the factory. Some improvements can be easily done to obtain a very nice picture.

Shielding

One of the most frequent problems is regarding the image noise. Isolating some parts of the PCB definitely help to mitigate this.

Image stability

Image stability can be improved by cleaning the sync output. This can be done by means of a LM1881 sync splitter with a very simple circuit. Details of different experiments regarding the use of the LM1881 and the performance obtained can be found here: https://tomdalby.com/other/gbs8200.html

Additionally, replacing the capacitor at the 3.3V regulator by a quality tantalum one will help to obtain a more stable voltage, also improving the stability.

GBScontrol

Definitely, the most nice hack for the GBS8200 board consist in using the GBScontrol firmware instead of the fabric one. This firmware runs on a ESP8266 processor, and can be easily incorporated to the GBS8200 using a NodeMCU. Only power and I2C connections are neccesary!

GBScontrol adds a very nice control panel, improves the image quality and all can be controlled with a web-based application and accessed via wifi.

GBScontrol firmware can be downloaded here: https://github.com/ramapcsx2/gbs-control

Adjust RGB pots!

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