GBS Control

I came across a video on the GBS Control upgrade project for the GBS8200 boards. I had been interested in the GBS8200 back when I was doing my Commodore 128 RGBi/CGA to RGB video adapter. I had went with a SCART to HDMI adapter, as at the time that looked to be a better solution. It seems that device puts in a lot of delay though. It is useful to get “something” out of old RGB devices onto a HDMI compatible display, but when doing something like playing games the delay introduced is bad. I had not previously seen anything on the GBS Control project. The reason I had not used it at the time, was the SCART was to HDMI, where the GBS8200 outputs to VGA. The GBS8200 was a bit questionable too as it wasn’t super well liked in some circles at least.

GBS Control Project
https://github.com/ramapcsx2/gbs-control

Voultar’s Build Video
https://www.youtube.com/watch?v=1AVXhiTlmgo&t=2382s

GBS Control Case I used

https://www.thingiverse.com/thing:4946190

There is now the GBS Control project, which involves wiring in an ESP board to take over control of the board. This greatly reduces the delay introduced in the output. It accepts input from 15kHz (or 31kHz) RGB/HV (VGA), RGBS (RGB Sync often wired with SCART or 4 RCA jacks) and YUB (Component) and outputs to regular 31kHz VGA. There are DAC nonbuffered based VGA to HDMI adapters that are available very cheaply as well that are said to not introduce additional lag.

It has various features beyond near no lag being introduced. It has Scan Line emulation, various resolution outputs, downscaling video from higher resolution to lower resolution output. The controls are all onboard the ESP web interface, which you can use by using the default broadcast it does, or link it to your wifi network. It also lets adjusting position, size and various other things with the output.

In my case, I went with a compact case that was based on the build instructions I followed from a video by Voultar that introduced me to the project. With the case I used I don’t have the RGBS input accessible which is wired to a SCART port. It does seem though RGBS input is an option into the 15pin VGA style port with Sync on the HSync pin. HV means Horizontal and Vertical Sync, where RGBS just uses a single Combined Sync or CSync signal. The case turned out great, it is a near perfect fit.

I made a few changes compared to Voultar’s instructions. First, I did not add the resistor to the Sync line for the RGBS, as with it that affects the RGBHV input from what I read, so if I did do it. I would want to wire up an input option to switch between it being in place and disabled. On going over what that is about, I believe it is to be there when devices use TTL Sync a 5V Sync Signal instead of the 1V max Sync that RGBHV generally uses. The next change I made was when soldering in the ESP board I used angled header pins for the two ground connections, that provides a much sturdier connection between the two boards than a piece of copper wire or solder only. In most cases either just solder, or at least using a bit of wire will likely be just fine though. I like that if it gets dropped the pin headers will be a lot sturdier. I also connected the power for the frequency generator to a different capacitor, Voultar had misspoken what the polarity was in his video while wiring up the power, that let me wondering if he was wiring it correctly or not. I decided to then go with how the project instructions at gitub showed it wired in. Voultar’s wiring was a little shorter for the power, but it was also a little harder to get in at it with the soldering iron. For all of the power wiring I used heavier wire, and for the various other low power wiring I used solid core 30awg wrapping wire. I found that I had issues with the solder points on the two chips with the adjacent pins getting bridged, and had used some desoldering braid to get rid of the bridges. More flux would have likely helped me avoid bridging the pins. Voultar has certainly done that kind of thing far more than I have. Thankfully there are only 4 solder points to various chip legs. The capacitors were easier to stack than I expected and they turned out very well.

Mostly I want it to use the GBS Control with my RGBI to RGBS or RGB/HV converter project I posted previously for the Commodore 128 80 column RGBI (CGA) mode.

CGA/RGBI to RGBS Adapter: CGA/RGBI to RGBS Adapter Post

I have more recently made an update to that projects with a PCB and 3d Printable Case design.
Part 2: CGA/RGBI 2 RGBS PCB Design, Schematics, BOM

Part 3: CGA/RGBI 2 RGBS Board Assembly and Testing

Part 4: CGA/RGBI 2 RGBS Adapter Case and Release Files

I want to make a 5V output port for the VGA to HDMI DAC adapter at some point. I may do an audio passthrough option going in the front and out the back to connect into the adapter as well. I had thought of a power switch, but I use power strips for my equipment and generally turn them off when not in use. I have thought of a power LED as well, but still not sure on that one either. There was a version of the case that included putting the VGA to HDMI DAC adapter in the case. That was setup to remove the VGA output though, which I didn’t like. I have a number of VGA monitors I like to use from time to time.

For my first test of the unit, I connected it to the VGA output of a laptop. It passed through the VGA signal to the VGA output just fine. I then connected my Commodore 128 and my Digital RGBI to Analog RGBS / RGB/HV adapter. I built that adapter with the GBS8200 board in mind, so while it is setup it as RGBS + Audio through to the SCART connector I have configuration jumpers on the board. I changed the jumpers to NOT put 5V to the one pin which was to be the SCART mode detection. I also changed the Audio to not go to the HD15/VGA type connector and instead go to the RCA jack on the side. I changed the jumper to RGB/HV mode where it bypasses the Sync combiner circuitry on my adapter and outputs H Sync and V Sync. When connecting it up it worked great, I just adjusted some settings in the web interface to see how that worked out. The Scan Lines look pretty nice on it. I did not have any 80 Column mode programs prepared to use on the Commodore 128 to check it out too much at this time though.

This GBS Control is a baseline model build, more or less, for a bit more complex build check out the newer post linked below when I built a new unit and upgraded the one above to the new specification.

I have built another GBS Control and updated this GBS Control with some more connector options and features. 

You can view that post here: https://hobbytronics.home.blog/2023/12/18/a-new-improved-gbs-control-and-upgrades/