cga to vga converter uPython

Are you looking for something like this RGB to VGA adapter? They cost about $1.

I think they mean the old IBMPC Color Graphics Array RGBI TTL output

https://en.wikipedia.org/wiki/Color_Graphics_Adapter#DE-9_connector_for_RGBI_monitor

I think Ben did two shows with FPGA.

Ben Heck’s Giant Game Boy Episode -- Episode 225
/challenges-projects/element14-presents/benheck/ben-heck-exclusive/w/documents/1370/ben-heck-s-giant-game-boy-episode----episode-225

https://github.com/thebenheckshow/225-tbhs-Giant-Game-Boy/tree/master/DE0_GameBoy_DMG-01_VGA-master/Software

Ben Heck's FPGA LCD Driver Hack Episode -- Episode 169
/challenges-projects/element14-presents/benheck/ben-heck-exclusive/w/documents/18694/ben-heck-s-fpga-lcd-driver-hack-episode----episode-169

https://github.com/thebenheckshow/169-tbhs-FPGA-LCD-Driver-Hack

Amazing how expensive the iCEstick has become. I got it for about £25 a couple of years ago. Now it is >£120. Fortunately easy to replicate, since it's just a TQFP chip.

looks interesting and did not find by my own

Ouch! I must have got mine just in time then. You were lucky to get then a couple of years ago as they were very difficult to get hold of due to the supply chain issues.    

Something like the Olimex board might be a cheaper alternative these days: 
https://www.olimex.com/Products/FPGA/iCE40/

I was going to suggest this:

https://www.aliexpress.com/item/1005006165197426.html

But the learning curve with the Olimex and iCE40 will be easier.

MK

how the speed of an fpga is measured, compared, what should i look for if selecting for a project?

It's very, very difficult.

You need to delve quite deeply into the data sheets.

The things to look for are the IO toggle rate, maximum clock rate of internal RAM, and maybe some benchmarks of complete designs although comparing across manufacturers is very hard with real designs.

Another issue is that all manufacturers offer different speed versions and the fastest ones in the data sheet may not be readily obtainable.

Very roughly, in ascending order of speed:

iCE40: slow but very low power

Gowin Little Bee: very similar to Lattice XP2

Lattice XP2

Intel/A;ltera  MAX10

Efinix Trion

AMD/Xilinx Spartan 3

AMD/Xilinx Spartan7

AMD/Xilinx Artix7

I would recommend Lattice iCE40, Intel Max10,  Efinix Trion, Gowin Little Bee in that order for a beginner.

Huge jump from Circuit Python to any of those.

Key things in choosing are availability of chips, dev tools and support.

If your volumes are small there will (usually) be very little support from the manufacturer.

The Gowin is supported by very cheap tools from China (Aliexpress)

This board might suit you because it has some video hardware built in - the Intel/Altera tools are free. I did a blog about this board a while ago:

 Kamami MAXimator FPGA Board 

It's not the cheapest route but might suit your application.

MK

This may be why:

"...I found out that the GBS-8200 and knockoffs only work with composite sync on signals that are below VGA frequencies..."

https://www.insentricity.com/a.cl/219/cgargbi-to-analog-for-the-commodore-128

I googled the other day (on mobile, I didn't keep the links) and found cgavga and cga2vga projects on GitHub, that would be worth the OP checking out too. I couldn't tell if they were any good or not (and one was using a HDL I'd not heard of), but there certainly seems to be resources out there. Time to get 'hands dirty' and try one of them out. If it fails and a different approach is needed then it's just a week or two of knowledge that will come in handy later for a beginner anyway. 

rlaci said:

and what is the whole approach to make it work

I just remembered that Micah did a fairly in depth LED video matrix panel driver project using Icestudio with an iCEBreaker FPGA board, which may be of some interest. The live stream recording is available here: 

https://www.youtube.com/watch?v=IMIKTuaKBwI

https://www.youtube.com/watch?v=fwhXM4oo8Gs

https://www.youtube.com/watch?v=n3q17l1Zcus

https://www.youtube.com/watch?v=MrrhLd4ddpg

https://www.youtube.com/watch?v=3lnWdN8G40g

https://www.youtube.com/watch?v=QxtYy0Wb1S0

There is also an edited down version but you'll miss out on a lot of the detail.

rlaci said:

and what is the whole approach to make it work

I just remembered that Micah did a fairly in depth LED video matrix panel driver project using Icestudio with an iCEBreaker FPGA board, which may be of some interest. The live stream recording is available here: 

https://www.youtube.com/watch?v=IMIKTuaKBwI

https://www.youtube.com/watch?v=fwhXM4oo8Gs

https://www.youtube.com/watch?v=n3q17l1Zcus

https://www.youtube.com/watch?v=MrrhLd4ddpg

https://www.youtube.com/watch?v=3lnWdN8G40g

https://www.youtube.com/watch?v=QxtYy0Wb1S0

There is also an edited down version but you'll miss out on a lot of the detail.