RGB to HDMI using a Pi Zero and a small CPLD

[IanB]

Thanks, I have a big box of stand offs, probably all the wrong size.
...
Ordered 4 transparent cases, only need 3 but at that price and the fact it takes a while to come, I ordered a spare.

I just noticed that although it is otherwise indentical, the transparent case has different mountings to the black one, the support posts and their screw holes are much smaller in the transparent case and it comes with small self tapping screws which aren't even long enough to reach through the Pi board to actually secure it

I drilled out the support pillars using a 2mm drill so the stand offs could be screwed in but you have to be careful as the support pillars are already so much smaller they might split.

I also cut / filed about 1.5 - 2 mm off the stand off threads so they don't have to be screwed in so far. (This may be worth doing even with the black case as the thread bottoms out in the screw holes and they are quite hard to screw in all the way)

One advantage with the transparent case, you don't actually have to drill holes for the LEDs

[Elminster]

Ah ok thanks. Well I have one spare case, or will do, and a lot of hot glue. Well see how far I get.

[f82]

Hi,

I was reading about this great project and I was thinking if this would theorically work, maybe with some specific customization, also with other old PAL 50hz game console that had rgb output to scart like the Megadrive. Lately I was considering a scaler/converter to output the video to a vga/hdmi monitor but prices and input output latency are the problem usually.

Thank

[hoglet]

I was reading about this great project and I was thinking if this would theorically work, maybe with some specific customization, also with other old PAL 50hz game console that had rgb output to scart like the Megadrive. Lately I was considering a scaler/converter to output the video to a vga/hdmi monitor but prices and input output latency are the problem usually.

I've just looked up the video specs on the Mega Drive:
https://segaretro.org/Sega_Mega_Drive/Palettes_and_CRAM

The system outputs 9-bit colour (i.e. 3-bit Red, 3-bit Green, 3-bit Blue) and the resolution is 320x240 (PAL) and 320x224 (NSTC).

I think in principle the software on the Pi could deal with this data rate.

Unfortunately, none of the current front end capture boards (for the Beeb or the Atom) support the digitization of 3-bit/pixel colours. For that, a new design would be needed, probably using three proper high-speed Video ADC devices, such as three AD9057 convertors:
https://uk.rs-online.com/web/p/video-adcs/7095115/

I'm not planning such a design, at least not in the short term anyway.

Dave

[f82]

I was reading about this great project and I was thinking if this would theorically work, maybe with some specific customization, also with other old PAL 50hz game console that had rgb output to scart like the Megadrive. Lately I was considering a scaler/converter to output the video to a vga/hdmi monitor but prices and input output latency are the problem usually.

I've just looked up the video specs on the Mega Drive:
https://segaretro.org/Sega_Mega_Drive/Palettes_and_CRAM

The system outputs 9-bit colour (i.e. 3-bit Red, 3-bit Green, 3-bit Blue) and the resolution is 320x240 (PAL) and 320x224 (NSTC).

I think in principle the software on the Pi could deal with this data rate.

Unfortunately, none of the current front end capture boards (for the Beeb or the Atom) support the digitization of 3-bit/pixel colours. For that, a new design would be needed, probably using three proper high-speed Video ADC devices, such as three AD9057 convertors:
https://uk.rs-online.com/web/p/video-adcs/7095115/

I'm not planning such a design, at least not in the short term anyway.

Dave

Thank you. It would be nice to have this device supporting these console and I was hoping it would have been just a matter of different software configs.
I hope for the future to see a newer design supporting it!

[trixster]

Hi,

I was reading about this great project and I was thinking if this would theorically work, maybe with some specific customization, also with other old PAL 50hz game console that had rgb output to scart like the Megadrive. Lately I was considering a scaler/converter to output the video to a vga/hdmi monitor but prices and input output latency are the problem usually.

Thank

It’s not cheap at £100+ for a prebuilt one, but the OSSC is a sound purchase for rgb games consoles, especially if you use a scart switch to connect multiple devices to it. Virtually zero lag and lots of options for sync and output. Works well with rgb computers too.

[marcusjambler]

Interested in a PCB if there are some

Marcus

[hoglet]

Interested in a PCB if there are some

I don't have any boards at the moment, but Daniel might have some still.

[IanB]

Interested in a PCB if there are some

Looks like someone has listed their surplus ones on ebay:

https://www.ebay.co.uk/itm/PCB-for-the- ... 3516528081

[hoglet]

It would have been nice if this vendor had asked permission.

He also seems to have mangled the silk screen.

Dave

[bprosman]

Sue him Dave

[Elminster]

He also seems to have mangled the silk screen.

Just checked silk screen on the ones I had done at seeed recently and they are fine. Perhaps he didn't use seeedstudio.

[hoglet]

Sue him Dave

I've just been contacted by Tim (retrobrewcomputing on ebay) who has explained the situation, and I'm happy for him to sell the spare boards that he has. They are the most recent (v4) version.

Dave

[Elminster]

Any idea what happened to the silk screen? I am sure mine were the latest board and checking them silkscreen looks fine.

Got me wondering now if I uploaded the wrong gerbers.

[twoangrybears]

Hi

I am the guilty party (Tim/retrobrewcomputing) who listed these PCBs without contacting @Hoglet first Thank you Dave for being so gracious about this and for giving me the clue I needed to register here (my ad blocker was stopping a cookie I needed to accept). It's nice to be here finally.

@Elminster I used JLCPCB to print the boards because I was in the middle of placing an order with them already rather than using seeed and I think the silk screen error crept in there. I will examine them more closely later to see if there is anything else but at first glance it looks as if the newline character between each line of the copyright message has been interpreted as a literal backlash followed by a "n" ("\n") rather than inserting a line break so three lines have been written as one line.

[Elminster]

Thanks for clearing that up. I shall rest easy, I checked mine and all look fine. Not built this batch yet.

[bprosman]

Glad you worked it out.

[IanB]

I was asked in a PM if this adapter would work with a Spectrum so I did a bit of investigation. The original Spectrum only had multi level YUV internally so there is no simple way to get it working although a similar interface to the Atom board to convert YUV to TTL RGBI could be designed.

However it looks like it would be very easy to get it working with the Spectrum 128, +2, +2A and +3
According to this info:
http://www.fruitcake.plus.com/Sinclair/ ... TCable.htm
The spectrum 128 and +2 output TTL RGBI (4 bits) and that could be connected straight to the BBC converter with an appropriate profile using the same mods I did for PC CGA which is also RGBI.
The Spectrum +2A and 3 output analog RGB which isn't suitable but it looks like they have the TTL RGBI internally so those signals could be picked up and again connected directly to the BBC converter.

[sirmorris]

If you need a spectrum edge connector I can sort you out.

[MadeGray]

Glad everything was cleared with Tim (retrobrew) I’ve just ordered a couple (very nice chap by the way with his response to the order) I’ve no connection but does seem a good chap if he’s supply these literally at cost and as said glad cleared up with Hoglet.

Im aiming to practice my surface mount skills on these and CPLD programming etc as it encompasses all those elements.

Thanks everyone. I’m sure I’ll have plenty of questions!

John

[Elminster]

For anyone going to Cambridge, if I remember to take them, I may have some spare boards to give out.

[JonC]

If anyone decides to do a run of built boards, I'd be interested. Regrettably the soldering level required is beyond my skill level.

[tynemouthsoftware]

Looks an interesting project, I will have to build one.

I've not looked in detail at the code (yet), but I wonder, is there any point where a whole frame of video is held where it could be exported to an image file? I ask this as I am never very good at taking screenshots from a monitor with a camera, which I often need to do to illustrate my blog posts. It would be quite handy if one of the buttons (or an extra one) could be configured to save a screenshot image of the current frame, either to the SD card, or a USB drive maybe?

I appreciate this might cause the output to drop frames whilst processing that, but maybe whiting out the screen would be a good indication it had taken a picture anyway?

Thanks,

Dave

[hoglet]

I've not looked in detail at the code (yet), but I wonder, is there any point where a whole frame of video is held where it could be exported to an image file? I ask this as I am never very good at taking screenshots from a monitor with a camera, which I often need to do to illustrate my blog posts. It would be quite handy if one of the buttons (or an extra one) could be configured to save a screenshot image of the current frame, either to the SD card, or a USB drive maybe?

That feature was added to the dev branch about two months ago.

It works pretty well, and writes a PNG file to the SD card.

Here's an example from an Atom:

Here's a second example, posted earlier by Ian from a PC:

There is a pre-release available containing this code here:
https://github.com/hoglet67/RGBtoHDMI/r ... 10_49320d4

(the title suggests this is an Atom Specific release, that's actually not the case)

Dave

[tynemouthsoftware]

Great, thank you. I'll check out that branch.

Dave

[hoglet]

Great, thank you. I'll check out that branch.

I just added a couple of examples to the post above.

[SimonSideburns]

I don't know what it is about Windows 3.1x but seeing the Program Manager like this brings back many memories of when I used to use Windows back in the day. Everything was much simpler back then.

[Elminster]

I have just got around to using Dec 2018 pi version. Was confused by the right led till I read this now meant it was running in mode 7. But this is an Electron that doesn’t seem right, and I just get a blank screen. Same on both original Jed code and latest Jed (I have 2 RGBtoHDMI). The 2017 pi code runs fine on both.

Am I missing something new I need to do setting wise? Other than the usual elk=1 and mix=1? I will test on a beeb when I get chance.

[hoglet]

I have just got around to using Dec 2018 pi version. Was confused by the right led till I read this now meant it was running in mode 7. But this is an Electron that doesn’t seem right, and I just get a blank screen. Same on both original Jed code and latest Jed (I have 2 RGBtoHDMI). The 2017 pi code runs fine on both.

Both LEDs should be green!

I would recommend using the 20190510_49320d4 Pi release (i.e. the latest dev release, which is very stable).

Use a clean SD card (i.e don't just unzip ontop of an old version)

I would also recommend using the 6.4 CPLD release from the dev branch, links are here:
https://github.com/hoglet67/RGBtoHDMI/w ... rogramming

(I really must get around to merging the dev branch back into master)

If you still have problems, connect a serial cable and post a log.

Dave

[Elminster]

Will try newer newer versions

Yes I have 3 cards, and newer ones were Freshly format. Nothing has been copied over anything. I have multiple versions on multiple cards. I wasn’t going to delete original till I got newer one working.

I though instruction said second led was mode 7 lock, maybe I misread.