Atom Video to HDMI Adapter

discussion of games, software, hardware & emulators relating to the Acorn Atom and Acorn System machines.
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Elminster
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Re: Atom Video to HDMI Adapter

Post by Elminster » Thu Sep 26, 2019 8:21 am

-B- wrote:
Thu Sep 26, 2019 8:02 am
.... 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.

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Elminster
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Re: Atom Video to HDMI Adapter

Post by Elminster » Thu Sep 26, 2019 8:26 pm

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

Attached if useful to anyone in future.
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rgb-to-hdmi-Atom_template.pdf
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-B-
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Re: Atom Video to HDMI Adapter

Post by -B- » Thu Sep 26, 2019 8:52 pm

Here’s some quick measurements of my box.

7364B32C-1F71-4AAD-97BD-9D24CC30A46F.jpeg
D36183E0-329D-4BB4-819A-0E1E04C73CA5.jpeg
Atom | BBC Model A | BBC Model B | Electron | Olivetti PC128S.

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Elminster
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Re: Atom Video to HDMI Adapter

Post by Elminster » Thu Sep 26, 2019 9:16 pm

Great thanks.

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

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hoglet
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Re: Atom Video to HDMI Adapter

Post by hoglet » Thu Sep 26, 2019 9:21 pm

Elminster wrote:
Thu Sep 26, 2019 9:16 pm
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

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Elminster
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Re: Atom Video to HDMI Adapter

Post by Elminster » Thu Sep 26, 2019 9:58 pm

hoglet wrote:
Thu Sep 26, 2019 9:21 pm
Elminster wrote:
Thu Sep 26, 2019 9:16 pm
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?

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-B-
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Re: Atom Video to HDMI Adapter

Post by -B- » Fri Sep 27, 2019 9:03 am

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

89ACABCB-1898-4141-BD02-7599530C2C94.jpeg
Atom | BBC Model A | BBC Model B | Electron | Olivetti PC128S.

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Elminster
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Re: Atom Video to HDMI Adapter

Post by Elminster » Fri Sep 27, 2019 9:16 am

-B- wrote:
Fri Sep 27, 2019 9:03 am
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.

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anightin
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Re: Atom Video to HDMI Adapter

Post by anightin » Fri Sep 27, 2019 10:16 am

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

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Elminster
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Re: Atom Video to HDMI Adapter

Post by Elminster » Fri Oct 11, 2019 4:19 pm

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 .......
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IMG_5614.png

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oss003
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Re: Atom Video to HDMI Adapter

Post by oss003 » Thu Nov 21, 2019 8:15 pm

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

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hoglet
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Re: Atom Video to HDMI Adapter

Post by hoglet » Thu Nov 21, 2019 9:04 pm

oss003 wrote:
Thu Nov 21, 2019 8:15 pm
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

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Re: Atom Video to HDMI Adapter

Post by oss003 » Thu Nov 21, 2019 9:27 pm

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

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Re: Atom Video to HDMI Adapter

Post by hoglet » Thu Nov 21, 2019 9:35 pm

oss003 wrote:
Thu Nov 21, 2019 9:27 pm
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

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Re: Atom Video to HDMI Adapter

Post by oss003 » Fri Nov 22, 2019 4:08 pm

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

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roland
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Re: Atom Video to HDMI Adapter

Post by roland » Fri Nov 22, 2019 4:28 pm

Maybe we can use some of these features in the Godil or FPGAtom :D
FPGAtom: much better than Atom2k15 which was even better than the real thing.
MAN WOMAN :shock:

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Re: Atom Video to HDMI Adapter

Post by oss003 » Fri Nov 22, 2019 8:25 pm

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

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

Greetings
Kees

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IanB
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Re: Atom Video to HDMI Adapter

Post by IanB » Mon Dec 02, 2019 6:19 pm

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:

Atom.jpg

Closeup of the analog board with mods:

Closeup.jpg
Last edited by IanB on Mon Dec 02, 2019 6:27 pm, edited 1 time in total.

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Re: Atom Video to HDMI Adapter

Post by -B- » Mon Dec 02, 2019 6:24 pm

Excellent work =D> again!
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Re: Atom Video to HDMI Adapter

Post by oss003 » Mon Dec 02, 2019 6:52 pm

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

Greetings
Kees

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Re: Atom Video to HDMI Adapter

Post by hoglet » Mon Dec 02, 2019 7:06 pm

IanB wrote:
Mon Dec 02, 2019 6:19 pm
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

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Re: Atom Video to HDMI Adapter

Post by IanB » Mon Dec 02, 2019 7:44 pm

hoglet wrote:
Mon Dec 02, 2019 7:06 pm
Is the issue that you need different thresholds for Y and PA/PB?
Yes
hoglet wrote:
Mon Dec 02, 2019 7:06 pm
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
Last edited by IanB on Mon Dec 02, 2019 7:48 pm, edited 1 time in total.

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Re: Atom Video to HDMI Adapter

Post by IanB » Mon Dec 02, 2019 7:47 pm

oss003 wrote:
Mon Dec 02, 2019 6:52 pm
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.

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Re: Atom Video to HDMI Adapter

Post by hoglet » Mon Dec 02, 2019 8:01 pm

Thanks for the detailed response Ian.

Dave

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