Oric-1 RGB to SCART - pin 8?

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tingo
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Oric-1 RGB to SCART - pin 8?

Post by tingo » Tue Jan 22, 2019 11:27 am

Hello,
I'm going to make a RGB video to SCART buffer, as described here http://www.defence-force.org/computing/ ... are/video/
for my Oric-1.
I have read all the old threads about video out to SCART on the Oric, and nowhere is pin 8 on the SCART connector mentioned, which is defined as

Code: Select all

Pin 8		Status & Aspect Ratio up[c]
		    0–2 V → off
		    +5–8 V → on/16:9
		    +9.5–12 V → on/4:3
will the SCART circuit work without this signal?
FWIW, I'm going to convert it to a SCART to HDMI converter, not a SCART TV.
Torfinn

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Re: Oric-1 RGB to SCART - pin 8?

Post by Chema » Tue Jan 22, 2019 2:44 pm

I am quite sure I had mine unconnected. But my TV is a 4:3 old CRT...

The full process is illustrated here (by Peacer) viewtopic.php?f=8&t=989&p=8964&hilit=rgb+cable#p8964

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Re: Oric-1 RGB to SCART - pin 8?

Post by tingo » Tue Jan 22, 2019 4:13 pm

Thanks for the information.
For now I wired pin 8 of the SCART connector to + 5V with a jumper. Then I can try unconnected or with + 5 V at least.
Torfinn

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Re: Oric-1 RGB to SCART - pin 8?

Post by mikeb » Tue Jan 22, 2019 5:33 pm

I'm pretty sure that pin 8 open (0v) will simply leave you at the mercy of your TV set.

Depending on the set, it may show

a) Correct aspect (especially if set is old and 4:3!)
b) Stretched/Squished aspect (16:9 set trying to stretch to fill)
c) Have a setting that let's you tell it: "This is a [4:3, 16:9, 21:9] picture and please [anamorphic stretch/crop/letterbox] it"

It's only a hint to try and tell the TV what to do, some older TVs may be too stupid to even use it anyway.

No harm leaving it disconnected and seeing what happens.

Oric's picture is 4:3, so using +5v to tell the TV it's 16:9 will likely give you a picture stretched horizontally to fill the screen, and circles will be very odd.

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Re: Oric-1 RGB to SCART - pin 8?

Post by tingo » Tue Jan 22, 2019 6:15 pm

Yes, I know, but it is easier to get at +5V - I already have that on the PCB. If I need higher voltage I'll just redesign the schematic with with a 5 V regulator (from 9 or even 12 volts).
Torfinn

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Re: Oric-1 RGB to SCART - pin 8?

Post by iss » Tue Jan 22, 2019 9:47 pm

In my opinion everything will depend on the SCART-to-HDMI converter and its possibilities to handle properly the input signal/voltage on pin 8. I don't have such converter but I remember that once I've tried one and it worked fine with normal simple (just wires) RGB-SCART cable with pin 8 connected to 5V. It was a cheap China converter.

@tingo: Can you share your model and its specifications (if available of course)?

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Re: Oric-1 RGB to SCART - pin 8?

Post by tingo » Tue Jan 22, 2019 10:36 pm

I don't know if it has a model number, I just bought this one: https://www.ebay.com/itm/TPX-Monitor-Bo ... 2127915565
Torfinn

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Re: Oric-1 RGB to SCART - pin 8?

Post by iss » Tue Jan 22, 2019 10:45 pm

It looks good! I bet it will work :).

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Re: Oric-1 RGB to SCART - pin 8?

Post by Chema » Tue Jan 22, 2019 11:48 pm

Post some pics when you have it working!

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Re: Oric-1 RGB to SCART - pin 8?

Post by Dbug » Wed Jan 23, 2019 6:29 pm

This black one is available in multiple places with slightly different variants, I do have one (from Ali Express) and it did display the Oric picture without any problem.

I had another one of a different type (the rectangular curvy one with a light blue stripe under the name), and that one did not work at all, good things these things are cheap :)

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Re: Oric-1 RGB to SCART - pin 8?

Post by Symoon » Wed Jan 23, 2019 8:40 pm

Atari and Amiga world have threads, from time to time, with VGA monitors that still support 15kHz (even if not documented).
I wonder if such screens could display our Orics?
If so how should we build the right cable?

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Re: Oric-1 RGB to SCART - pin 8?

Post by iss » Wed Jan 23, 2019 10:58 pm

This is SCART-RGB to VGA converter (we imagine that SCART is the same as Oric RGB output):
SCART2VGA_converter.gif
Source page found HERE.
The complexity comes from VGA requirement of separated Horizontal and Vertical Synchro signals.
I'm sure there are other solutions too.

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Re: Oric-1 RGB to SCART - pin 8?

Post by Symoon » Thu Jan 24, 2019 12:14 am

Aha, so I suspect Amigas and Atari ST are "VGA ready" when the Oric isn't (forgive newbie questions). This synchro signal thing rings a (very distant) bell

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Re: Oric-1 RGB to SCART - pin 8?

Post by tingo » Mon Feb 04, 2019 5:25 pm

OK, I made the circuit (actually made a PCB for it and milled it on a small PCB mill we have at our makerspace). When connected to a TV via SCART, I have a picture. Unfortunately, the picture rolls (unable to "lock" onto VSync?). Perhaps this means that my Oric-1 needs repair? I don't know yet.
Torfinn

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Re: Oric-1 RGB to SCART - pin 8?

Post by Dbug » Mon Feb 04, 2019 5:55 pm

Does the schematic split the Horizontal and Vertical parts of the signal?
Maybe the screen is confused because the Sync pin contains both the HSync and VSync signals?

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