Hi together,
I dived in this subject almost three years ago.
I wanted to connect my old C128D-CR to a modern Display ... I already own a CRT with a SCART input and an old split cable DIN-8 + D-SUB-9 to SCART with a switch for choosing 40 col. or 80 col. mode. I searched through the infinite internet and found something like CGA2RGB converters for the 80 col. mode and the GBS-8200 to connect the D-SUB-9 to the CGA2RGB converter and then the CGA2RGB converter to the GBS-8200 and finally a VGA or DVI Display to the GBS-8200.
Fine - winner, winner, chickens dinner
But what's about the 40 col. mode?
?
So I developed my own solution to connect a C128 to a SCART display device.
It is not perfect - the 80 col. mode ist nice but the 40 col. mode with the LUMA, CHROMA & COMPOSITE signals depends on the cable and the quality of the display device. Many TVs with a SCART input do not support S-VIDEO (CHROMA&LUMA) with SCART or have a bad qualitiy.
It is a mess ... doesn't make a lot fun. My device works the best with a CRT.
You can watch my video, if you are interessted.
https://youtu.be/qOvFwwrAEIkIn my opinion @Rasz is right.
If you want to connect a C128 to a modern display with good picture quality, you have to use:
1. build or buy the RGBtoHDMI converter
https://github.com/hoglet67/RGBtoHDMI/wiki with digital interface to use the 80 col. mode. You can connect the HDMI output of the Raspi Zero to the HDMI input of yout TV and enjoy the 80 col. mode of your C128
2. build or buy the C128 component video mod from c0pperdragon
https://github.com/c0pperdragon/C64-Video-Enhancement/issues/64 I pushed c0pperdragon a little to design a smaller version that fits into the C128. So it is possible to get component output of the VICII / 40 col. mode. Currently you can't buy the new version for the C128. You can buy and use a version for the C64
https://videogameperfection.com/products/commodore-component-video/, but it is too big to mount it into a C128. If that is done, you can connect this mod to the component input of your display. Then you can enjoy 40 col. mode on your big TV.
The best solution would be a further development of c0pperdragons way.
Designing and building an FPGA based solution to grab the necessary signals direct from both video ICs (VDC & VICII) and generate an HDMI output signal.
That sounds simple, but unfortunately it will be tricky.
Is there anybody with FPGA knowledge and time to do such a project?
It would be challenging
So cheers and RETRO ON.