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Post by hydrophilic on Jun 17, 2021 7:18:31 GMT
My buddy Sven Pook is making his version of a 40/80 col C128 adapter. V5 now has SVIDEO support. c128adapter.pook.nl/Thanks for sharing! The photo(s) on that website looks like a C128-SVideo (40-column) to SCART cable, with some added circuitry. This is new to me. However this thread is about 80-column video, direct to CGA/VGA monitor or possibly with adapter (possible to S-Video). Maybe I missed something on your linked web page about 80-column / RGBI conversion? Let us know if true; if not, there are other threads about S-Video where you should post your comment. Otherwise, 40-Column / S-Video users might miss your important information.
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Post by hydrophilic on Jun 17, 2021 7:40:56 GMT
That one has a nice design and is very affordable, but it does not have the "brown fix" (not a surprise at that price-point). I am currently using this adapter right now: github.com/JDet-74/C128toSCART_SMTYoutube: www.youtube.com/watch?v=qOvFwwrAEIkAt 38 EUR it is more expensive for a built unit, but comes in a nice box, has the brown fix and provides S-Video for 40 column as well (it can also be switched to FBAS/composite). The only thing missing is an option to turn off the "brown fix" so you get dark yellow. There just might be a reason in the future you want dark yellow... Otherwise it is close to perfect I think, but I am still probably going to need Sven Pook's adapter for "dark yellow" Thanks tokra! That looks like a great all-in-one device! Only issue for Americans is need to purchase SCART-to-SVideo or SCART-to-VGA cable. I "read" PDF from linked github; I have friend who has helped me with German, but a lot of my education came from a German version of C64 Programmer's Reference Guide . That PDF doesn't specifically mention "brown" or give schematics, although I haven't read all the docs on the github site. But I trust you when you say it has brown fix. Did you build this, or buy it somewhere? Since you mentioned price, I assume it is readily available, at least in Europe? BTW, I don't know why a casual user would want to turn-off brown-fix, but as a fellow hacker, I understand your feature request
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Post by hydrophilic on Jun 17, 2021 8:14:18 GMT
Update: I have not yet got an email response from the Canadian prototyper. He did warn me in previous emails he is slow to respond; hopefully it is just that and not lack of enthusiasm based on all the other options you guys reported and I emailed him about! I'm really glad to hear about all the other options you guys posted about. It is really nice there are options available for these vintage computers, even if they are hard to find. In the meantime, I got an email from "I Like 8 Bits" who built the same circuit discussed here; he posted a moderate/long-size blog post with lots of photos. WARNING: it is is for the do-it-yourself people, not a production-run for which this thread was created. [Edit] his blog post discusses multiple (3?) projects, but the first is about the C128 [/edit]
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Post by eslapion on Jun 18, 2021 18:28:18 GMT
Forgive my impudence but I see a couple of technical issues with your design.
For starter, since the output of the C128 RGBi port is digital, how come you need to have potentiometers ? These will require adjusting and I don't know exactly what people will use as reference to do that.
IMHO, you just need to use a high speed logic buffer such as 74AHCT245 which is compatible with the TTL levels of Commodore computers to restore the signal to full 0-5V rail to rail levels and then use a network of 1% tolerance resistors to convert the signals to analog values.
For another, there is absolutely no need to have a 12V input then 5V regulator on your board as you can just take the 5Vdc from the datassette port and perhaps clean it up with an LC filter.
Also, the dot clock on the 80 column output of the C128 is at 16MHz so using the finest surface mount parts to get a good quality video signal is important. IMHO, you should use TSSOP ICs and 0603 or 0402 discreet parts.
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Post by robertb on Jun 19, 2021 1:15:05 GMT
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Post by tokra on Jun 20, 2021 12:17:56 GMT
I "read" PDF from linked github; I have friend who has helped me with German, but a lot of my education came from a German version of C64 Programmer's Reference Guide . That PDF doesn't specifically mention "brown" or give schematics, although I haven't read all the docs on the github site. But I trust you when you say it has brown fix. Did you build this, or buy it somewhere? Since you mentioned price, I assume it is readily available, at least in Europe? BTW, I don't know why a casual user would want to turn-off brown-fix, but as a fellow hacker, I understand your feature request The PDF on the site linked above is in german as well as english, if you look at this file: github.com/JDet-74/C128toSCART_SMT/blob/main/C218toSCART_SMT_SETS_PRICES_SHIPPING.pdfit has the prices as well as shipping costs. I bought the built-version of it.
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Post by yovish on Apr 4, 2023 23:16:06 GMT
Hello! Despite the topic being 2 years old, let me add a few things from myself. I myself am currently designing my adapter for the Commodore 128, which will be able to display images from the A/V (40-column) and RGBI (80-column) outputs on a TV set via the EURO/SCART connector. From the EURO/SCART connector you can easily connect to a VGA or even HDMI monitor, via converters such as the GBS 8200/8220 (VGA) and the similar. My adapter has 4 palettes defined for images from the C128 in 80-column mode. The palettes can be switched "on the fly". I have pre-defined such palettes: 1. a palette with dark-yellow correction for brown; 2. a palette without dark-yellow-to-brown correction, such as in the Sven Pook adapter; 3. palette with colours as in 40-column mode - C64 colours; 4. a palette with colours like the VICE emulator. Each palette can be arranged from colours with RGB components in 8 intensity levels (3-bits D/A). Now I also want to add the possibility to convert from 80-column mode to S-Video and Composite Video signals. Since I am also very familiar with adapters from JDet-74 that correct dark yellow to brown, the GAL chip batch can be changed to not do this and display a dark yellow colour. I have done this myself and have 2 GAL chips that can be swapped. Here are these examples of my palettes.
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Post by xahmol on Apr 5, 2023 6:03:06 GMT
@yovosh: in case you are not aware, there is already such an adapter existing: c128adapter.pook.nl/It does not have palettes, but it gives great quality at a very low price. Hard to beat I think. On the other hand, if you want the best quality on RGBI including fully customisable palette, get an RGBtoHDMI. That quality is unrivalled and skips the whole SCART part. But with that you need a separate solution for 40 column, such as a Retrotink.
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Post by yovish on Apr 5, 2023 20:34:35 GMT
I know that such an adaptor by Sven Pook exists, because I mentioned it already. Please read my text again, but this time carefully.
I know the Sven Pook adapters well, I even have their schematics (V4 and V5). This is one of the simplest adapters for the C128. Unfortunately, in my opinion, the adapters from JDet-74 are currently the best for the C128 and give a better image and brown correction. My solution is a development of the adapters from JDet-74, with the difference that I can be more flexible with the colours. I know that there are some people who don't want the brown correction, but there are others who want it. My solution gives both possibilities and more.
I know almost all the solutions for the C128, and the current project is not the first. My solutions do not go beyond Poland for now, but that may change.
I will not impose on anyone what solution they should choose for themselves. I'm constructing an adapter for those who don't like compromises.
Besides, I don't know what's wrong with the EURO/SCART connector, which has the ability to support RGB, S-Video - Composite Video. It can also be used for trasmission of monochrome images if you need to.
Most advanced upscalers/converters need signals like those in EURO/SCART, and most often RGB in the form of analogue signals of a suitable level. Various adapters for the C128 include converting CGA-compatible RGBI signals to these analogue levels. Some do it better, others worse. If someone is satisfied with the quality of the adapter from Sven Pook, then OK. It's not good enough for me and many other people don't either.
And the mentioned RetroTINK cannot handle the signals from the C128 by itself and I need conversion to analogue RGB.
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Post by xahmol on Apr 6, 2023 3:51:00 GMT
@hobish: missed your reference to Sven Pook adapter. Sorry for that. But reading your reply, I still suggest to check the RGBTOHDMI. github.com/hoglet67/RGBtoHDMI/wikiThat one converts the RBGI signal to HDMI fully digitally, so avoiding any analogue interference transfer over SCART or S-Video will add. Without any need for another converter for the RGBI part. That is why I think using any analogue connector will always be a compromise as it will remain prone to interference. Also, for most people SCART is not the desired end connector by lack of a SCART enabled screen, adding the need for an additional converter further degrading quality. I actually have a SCART enabled Sony Trinitron CRT TV, but need HDMI for being able to capture on my PC without additional quality loss. The Retrotink in my setup is only needed as the RGBtoHDMI I have only does the RGBI part, so not 40 columns. The RGBtoHDMI signal does not need to go through that as it is already HDMI. Use the Retrotink for only 40 columns output. Sound directly goes via a USB enabled mixer to the PC in my setup, but can of course also be done by the Retrotink. See for quality of the RBBtoHDMI for example here: youtu.be/tMtlXj2Rrkgyoutu.be/kuJFZY3Dl38But of course fully OK if you want to build your own solution. Just wanted to point out existing alternatives for you in case needed, but also others reading this. My present view stays: if you want cheap and good quality, get the Sven Pook one. If you want no compromise, get an RGBTOHDMI fir the RGBI part.
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