cga to vga converter uPython

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

if you tell me how can i read asynchronously one line with the bit positions without any clock signal then reproduce it at the exact positions i would be very happy because i think its nonsense

as i experienced this VGA thing is pretty broadely understuud and sometimes there is a pixelclock for blank signals too sometimes nothing (actually measured it) and the VGA decoder chip sometimes reads a whole different resolution by its own as you are sending to and it all depends on the monitor side

i feel you do not like python but i think to use python for pio setup what part is assembler language and the same for c sdk im not sure what the problem is there especially if im using the DMA

yes it looks like a trivial task, but at high speeds some problems start to occur but you are right im a pretty beginner in microchip programming, im looking up the pico deeply now and would like to use that board as now i know it can do it for sure. i was switching between boards in the beginning, because i was not sure, please wish me luck or try to send some code to help if you want just stay positive please

If you're sure you wish to proceed with Pico, then it will require assembler programming for the Pico's internal PIO module(s).
The PIO is described in a user manual on the Raspberry Pi website (there are useful videos too, but everyone's primary source of info is the user manual), and there's lots of example code on the official GitHub site, but for sure there won't be a CGA to VGA converter, that's too niche. But there is very likely to be VGA output example code on the Internet for the Pico, so that you have something to examine.

To learn to use the PIO, that's best achieved by reading the manual (it is well-written and there are only half a dozen or so instructions to learn, although there's approx. half a dozen concepts that can be applied to each instruction type), and try to follow some example code to make sense of it, and then try to read in data, and try to write out data, and learn how to use DMA, and stick with C to interface your code. It's difficult enough to learn something new, than to try to layer on another programming language when the bulk of the examples will combine the PIO with C, not Python. If C is new, then that's not an overly difficult language either, and you might not need to learn a lot, if you get lucky and find examples close to the task you're doing. For instance, if you wish to "do something" once a line, or once a frame of data has been received, then look for examples which use DMA to transfer data from the PIO for _any_ purpose, and the PIO code, and C code there will be approximately what you need for that specific bit of functionality.

It's difficult to predict, but I think as a beginner, you may need to spend a week or so learning about PIO, trying some examples. If you're new to C, that requires a couple of weeks study and practice (I can recommend some books if you need that). Then expect to spend a further 3 weeks or so to experiment a bit, and design, develop and test your code (ballpark), and you may well have to scrap things and try different approaches, if you hit limits (because there are some limits with PIO), so it's best to experiment a bit first with some simpler projects, and examine with a 'scope, or other forms of debug, what's going on.

EDIT: Just realized beacon_dave has already shared an example of PIO for VGA output, so you've got something to begin learning.

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.