Atom Video to HDMI Adapter

[Elminster]

.... or someone could measure their box when they get home from work tonight and post the results here?
(I am volunteering).

Neil.

Or both so I can double-check.

If you have time I wouldn't complain. The one thing print a template wont tell me is where the side button hole is, so that would definitely be useful.

Thanks.

[Elminster]

Dodgy Template but seems to match up with the real thing. Will drill holes tomorrow probably.

Attached if useful to anyone in future.

[-B-]

Here’s some quick measurements of my box.

[Elminster]

Great thanks.

Even with the template and measurements I am sure I will get it wrong and end up with 4 inch holes anyway

[hoglet]

Even with the template and measurements I am sure I will get it wrong and end up with 4 inch holes anyway

If you have any, I recommend using "lip and spur" drill bits (also called a brad point bit or dowelling bit), as these give a cleaner cut.

Normall HSS drill bits just seem to melt the plastic leaving a crater rather than a clean hole!

Dave

[Elminster]

Even with the template and measurements I am sure I will get it wrong and end up with 4 inch holes anyway

If you have any, I recommend using "lip and spur" drill bits (also called a brad point bit or dowelling bit), as these give a cleaner cut.
brad_point_bit.jpg

Normall HSS drill bits just seem to melt the plastic leaving a crater rather than a clean hole!

Dave

I just know them as wood drill bits, yes I do have some.

I usually find if you use a small bit HSS bit and then use a larger one on plastic it is usually okay unless these particular boxes from Rapid are unusually bad?

[-B-]

I use a Philips screwdriver for the 3mm holes and one of these for the 4mm and deburring. By hand, not with a drill.

[Elminster]

I use a Philips screwdriver for the 3mm holes and one of these for the 4mm and deburring. By hand, not with a drill.

Ah yes, a step drill bit would be similar to increasing the hole size gradually. i've never actually bought any of those.

[anightin]

For the graphics sheet to overlay the holes I found the following very useful to punching clean holes through the paper:

https://www.ebay.co.uk/itm/0-5mm-10mm-S ... 2749.l2649

[Elminster]

Oops forgot to post that I had complete the RGB case. A slight accident with a hole being in the wrong place, all I can think of is the template slipped as everything else was in the right place. Anyway, I am no going to worry about it. The buttons are level with the surface just because I used ones I already had.

I only used the measurement to check the side button, which I got spot on thanks to the info above, in hindsight I should have double-checked the top, but that was a week before my new glasses turned up ... More haste less speeed.....

Now all I need to do is buy an Atom to actually put the RGB and Noise killer in .......

[oss003]

I am wondering ......... will this Atom Video to HDMI adapter also work for a Dragon, or any other system with a 6847?
The Dragon also has a 6847, only 8 colours in textmode.

Greetings
Kees

[hoglet]

I am wondering ......... will this Atom Video to HDMI adapter also work for a Dragon, or any other system with a 6847?
The Dragon also has a 6847, only 8 colours in textmode.

Yes, it should be possible to make this work with a Dragon.

You would need to attach some wires directly to the 6847 to pick up some of the signals that are on PL4 on the Atom (OA, OB, CHB)

Dave

[oss003]

The only difference between the Atom and Dragon is pin 9, video out ....

[hoglet]

The only difference between the Atom and Dragon is pin 9, video out ....

I agree, the Y amplifier is different, and the Y output includes the colour subcarrier from the LM1889.

So you might also have to desolder R65, so the Y output is back to monochrome.

Do you have a Dragon?

I have just have a bare mainboard (which I've been using for testing ICE-6809).

I don't even have a keyboard.

Dave

[oss003]

I don't have a Dragon.

I was chatting with Pere Serrat, who wrote the Dragon AGD port, and he told that he was working on a CocoVGA project for the Dragon. This is an FPGA board which has to be located in the 6847 socket and the 6847 goes back on the new board.
The function of the board is the abillity to change the colours in the pallet by software. Nice poject ...

https://youtu.be/OqsV8ucj1NQ

So I thought that maybe the Atom Video to HDMI would also be a nice Dragon addition because IIRC, you can select a colour pallet with the Pi.

Greetings
Kees

[roland]

Maybe we can use some of these features in the Godil or FPGAtom

[oss003]

Here are some examples of Coco games with a changed colour palette.

http://www.nickmarentes.com/ProjectArch ... emenu.html

Greetings
Kees

[IanB]

I've got the new Analog interface for the six bit version of RGB to HD working with the Atom using a few simple mods so I think the next issue of the analog PCB will have the ability to work with the Atom (and 6847 chips in general):

The colours are wrong because a YUV signal is being sent to an RGB palette. I've got to make some changes to generate a YUV palette instead:

Closeup of the analog board with mods:

[-B-]

Excellent work again!

[oss003]

Nice job Ian, is that a screen with split palet mode?

Greetings
Kees

[hoglet]

I've got the new Analog interface for the six bit version of RGB to HD working with the Atom using a few simple mods so I think the next issue of the analog PCB will have the ability to work with the Atom (and 6847 chips in general):

I was wondering if this would be possible (and planning to try myself later this week).

Is the issue that you need different thresholds for Y and PA/PB?

Out of interest, what did your mods actually do?

Dave

[IanB]

Is the issue that you need different thresholds for Y and PA/PB?

Yes

Out of interest, what did your mods actually do?

1. Lift pin 14 of both U1 and U2 to isolate the Vsync and Sync inputs and then feed V and H sync from the Atom 10 way connector directly to the TTL header.
2. Lift Pins 2 & 9 of U2 to isolate the reference inputs of the Green channel
3. connect DACC to pin 2 and DACD to pin 9
4. Connect a 100nf capacitor from DACD to ground ( the other 3 already have one)
5. remove (or do not fit) 75R termination resistors and U5 analog switch

Then connect PA (R-Y) to Red, PB (B-Y) to Blue and Luminance to Green.

Software changes:
Add adjustment for DACD, Change Atom palettes to do YUV to RGB conversion.
This uses the standard CPLD, not the special Atom one.

To make this a fully software configurable RGB/YUV system, I would have to change to a 6 output DAC and also use a 4 pole analog switch to control termination on all 4 inputs. 4066 switches have on resistances in the 50R - 100R range so could be used without resistors as the terminators provided they can handle the current. The switches could be controlled via the DATA line through an RC time constant to filter out rapid transitions when reprogramming the CPLD and DACs

[IanB]

Nice job Ian, is that a screen with split palet mode?

Yes that's Dave's test software that switches between the two 6847 palettes half way.

[hoglet]

Thanks for the detailed response Ian.

Dave

[IanB]

I am wondering ......... will this Atom Video to HDMI adapter also work for a Dragon, or any other system with a 6847?
The Dragon also has a 6847, only 8 colours in textmode.

I just got the RGB/YUV interface board working with the dragon:

I don't have any software to run on it yet so I wrote a quick random line drawing loop to get some graphics on screen:

In the other palette:

[hoglet]

Nice...

Is the new analog board working as expected then?

[IanB]

Is the new analog board working as expected then?

It ended up working in a slightly different way than I envisaged with the 6847 sources (I had to make one minor track cut and link and use different input signals) but after that change it works really well with everything I've tried so far.

[chrisn]

I can report another successful build of the Atom RGB to HDMI board. It worked first time

I found a few minor issues with the documentation:

In the BOM, the link for the 1x2 pin straight female 0.1" header is wrong, it should be https://uk.farnell.com/samtec/ssw-102-0 ... dp/1668331 or similar.

And in the assembly instructions, I'd suggest changing the order so that you fit the capacitors on the underside of the board before fitting the IC sockets, then the remaining capacitors. I was following the instructions blindly and missed that Fortunately, there's just enough space to be able to solder with the IC socket fitted, but it was a bit fiddly.

I've also made up the noise killer board, but Farnell sent me a wrong IC, so I haven't been able to finish this yet. Trying to fit the board to the Atom, I found that there wasn't much clearance above the 6847, so I put in extra IC sockets to raise the board up a bit.

[hoglet]

I can report another successful build of the Atom RGB to HDMI board. It worked first time

That's great.

Regarding the Pi Software, the most recent release (20200224_6e0d72e - Release Candidate 6) also supports the Atom Board, and has lots more features. The picture quality is unchanged, so if that's all you care about there is no need to change.

In the BOM, the link for the 1x2 pin straight female 0.1" header is wrong, it should be https://uk.farnell.com/samtec/ssw-102-0 ... dp/1668331 or similar.

FIxed.

And in the assembly instructions, I'd suggest changing the order so that you fit the capacitors on the underside of the board before fitting the IC sockets, then the remaining capacitors. I was following the instructions blindly and missed that Fortunately, there's just enough space to be able to solder with the IC socket fitted, but it was a bit fiddly.

FIxed.

It is possible to solder them in from the underside, as the holes are plated through. I think that's what I did.

I've also made up the noise killer board, but Farnell sent me a wrong IC, so I haven't been able to finish this yet. Trying to fit the board to the Atom, I found that there wasn't much clearance above the 6847, so I put in extra IC sockets to raise the board up a bit.

Yes, I've done the same.

Thanks for the feedback, always very welcome.

Dave

[thecellartroll]

I would very much like a pair of these. Can the surface mount be achieved with a big standard Maplin solder station? I'm generally pretty crap at soldering...