SCART version from Russia.

[f0lken]

Hello, UzeBox people!
Yesterday (or today ?) at 3 a.m. moscow time I managed to launch UzeBox version with SCART interface. The picture is "snowy" and only my XORO tv showed it (samsung one failed with white screen and only sound).
Here are some pictures (click to enlarge) and video.







[youtube]http://www.youtube.com/watch?v=2eQb5wbr4fI[/youtube]

The PCB is custom made. (laser printer and CuSO4 + NaCl + H2O).
Those "pins" are routed for extensions. One for RGB coder (ad725), 2 for nes joysticks, one for midi, one for SD (but I made an error in eagle, so pcb was patched again)
Now scart is connected directly to rgb and sync right after capacitors on RGB. AD725 is not really rare right there, but expensive and all those sellers work only with organisations and wholesale byers. So, I want scart =) at first.

The problem is - the image is covered with snow.
I used R-2R dac schematic, but those resistors are pretty uncommon and have high precision level. I used 750 Oms, 1.5 Koms, 3Koms and so one. Everything else is quite the same as on earlier designs.

Next. I'm not good in electronics. I'm zx-spectrum and other old computers fanatic, and I have a little expirenece of making some extensions for them for known schematic and some basic fixing. But I don't even know how the transistor works, so don't blame me anyway.

Another word about programming. I read on this forum, that some people had trouble with USBTinyISP + avrdude. Dunno, it worked like charm through usb hub at MacOS with firmware and avrdude version from ladyada.net. But only through usb hub. Thanks for posting this fuse bits settings. That's my another weak side =).

So, can anyone suggest a solution for this "snow" ?

I've got a bootleg nes joystick (we have this stuff on sale - chinese nes clones) and tomorow I'm planning to wire it and eat some pinky in pacman. Hope I havent screwed up a schematics. Photos/videos will be later if anyone interested and I'll succeed.

Again, please help with snow issue. =)
Thanks in advance!
And sorry for my english =)

[uze6666]

Nice work!

As we don't have SCART interface in North America it's hard to say if the problem is related to the interface. This appears to me either as a sync problem or overshoots/undershoots in the video signal. I'd check the video signal first, do you have an oscilloscope with video triggering? This noise problem could be due to insufficient decoupling of the Atmega (try putting a 100nf in parallel with a 10uf tantalum between ground and vcc and insure the contacts are good). It could also be due to a floating ground somewhere. Insure all ground are connected correctly, specially the ones on the SCART connector.

-Uze

[f0lken]

Ok, I'll put more thick wires to ground and also check for shorting somewhere.
Don't have and oscilloscope.
Also I'll try to put all signals through resistors to get b/w picture through composite. Got schematic somewhere, will find it.
Can it be the power problem ? I'm using 7805 regulator and it's pretty hot. Also will try to power it from alternative source (direct 5v).
Again - no picture (white screen) on samsung tv... But those model are known by strange scarts - not friendly with all this diy stuff.

[paul]

Nice work, f0lken!

I think I'll start building mine after I get a chance to patch LePlatz up. A little hardware diversion should be fun.

[f0lken]

Uff... I did it =)

One 7805 dead, couple of routes on PCB became mess, but it works even in more minimalist version =)

Steps
1. Put additional capacitor, like Uze adviced. No effect
2. Made BIG ground. Messed with something, and 7805 gone. Fixed, found another 7805 in trash, soldered back. Little bit better, but still snowy.
3. Tried to shorten all those 3 capacitors on R,G,B. Hm... colors are more vibrant, image is better, but still snowy. Soldered wires instead of capacitors.
4. Suddenly put a finger on 7805 and got burnt. Ouch! It's hot like hell!
5. Soldered direct 5V from old AT PSU, made as lab source.
6. TA-DA!!! Electronics is a science about bad soldering, bad grounding and bad powersource. =)

It works! There are some shadows (vertical), but pretty usable, and I've got this effect on other consoles and hacked devices. Not a big deal.
No joystick for me today, pretty tired =). Tomorrow, I'll eat Pinky, I hope =)

Those capacitors will be soldered on AD725 daughterboard, if I'll get an IC... Anyway, it works!!

So, the problem was in 7805. It's not powerful enough ? What replacement can I use (popular one, please!).

Thank you for all your advices and encouragement!

Some pictures (sorry for first one, my dog became curious of what I was doing and pushed me =)).





And video:
[youtube]http://www.youtube.com/watch?v=TNaFhYDSduU[/youtube]

Again =) Please, advice 7805 replacement =)

[uze6666]

That's great news! Does you Samsung TV works too now?

A 7805 should be good enough. It's normal that it get very hot if you have a big voltage input. What were you using to feed power to the 7805? Any decent 9V DC regulated wall transformer should do. Higher voltage will work, but the 7805 will just heat more. Insure you use the capacitors as per the datasheet.

I'm very surprised that the timing code works fine on SECAM without modifications! Wondering if it would work also on PAL. Or is it irrelevant when using the SCART connector? Anyone familiar with these standards?

Anyhow, that's very cool...be sure to send me you schematic/PCB layout when it's done and stable, I will add it to the downloads section on the main site!

Cheers,

-Uze

[DaveyPocket]

I'm very surprised that the timing code works fine on SECAM without modifications! Wondering if it would work also on PAL. Or is it irrelevant when using the SCART connector? Anyone familiar with these standards?

I believe most new flat screens support multiple timings, not quite sure.

[uze6666]

Yeah, most newer TVs in Europe are supporting NTSC timing. I'm just wondering if the timing through the SCART RGB input happens to be the same as NTSC or it just adapts to the incoming timing. This could explain why F0lken's LCD TV works, but not his Samsung Analog one.

-Uze

[f0lken]

Hey all!
Fixed troubles with power. I reduced capacitors near 7805 (got nominals from datasheet) and replaced powersource. Works fine!
About putting my "designs". Actually, there is nothing to put - my PCB contains errors - that's my first experience in tracing. I used some wires to fix it. Actually I used free version of Eagle and plugin for freerouting.net (read about it here =)). That's all. And you definately need somebody with good artistic taste for beautiful routing =)

To use it with SCART, you should connect R,G,B, SYNC,GND, AUDIO to scart connector, also solder Rgnd, Ggnd,Bgnd, AudioGnd and CompositeInGND together and to GND. See SCART pinout on http://pinouts.ru/Home/Scart_pinout.shtml. Take RGB signals directly !before! 0.1mf capacitors.

VERY VERY VERY important.
Connect 160 Ohms resistor to 5v and route this signal to pin 16 of SCART - that will switch scart to RGB mode.

That's all! No AD725 needed. I'm planning a daughterboard with AD725, but buying it here is a problem (I already mentioned it).

Regarding Samsung. Those guys have not routed RGB signals on SCART - that's the problem and it's quite common for this vendor =). Only composite and (may be s-video - chroma + luma)

Regarding all those timings. Even russian brands of TVs now support pal/secam/ntsc. It adapts to the signal automagically, and you can always switch manually to desired system. The pins on scart are the same for all. I had only one issue on Dreamcast, when TV could not detect signal type, but manual switch solved problem.

Hope, everything is clear now.
Regarding creating PAL version of UzeBox. I expect more problems with screenmodes, syncing and timings. Actually, it should not be a priority task. I have seen the TV without NTSC last time on attic of our sub-urban house. In dust and garbage. Ah, and it was b/w and on lamps. Even strange Chinese Beasts do have NTSC in AV mode - http://community.livejournal.com/emulate_su/18802.html (use google translate to translate posting, but pics are pretty self-descriptive and brand of TV, too =)).

Now I'm fighting with bootleg joystick. Hope it's just a bad joystick entity =). Tomorrow or during this week I'll try to get a new one and if I'll succeed - expect more photos and videos.

[uze6666]

That's good news!

Actually, there is nothing to put - my PCB contains errors - that's my first experience in tracing. I used some wires to fix it. Actually I used free version of Eagle and plugin for freerouting.net (read about it here =)). That's all. And you definitely need somebody with good artistic taste for beautiful routing =)

If you already drawn the schematic in Eagle and it works fine, that will do for me. That will certainly entice some folks in Europe to build it, specially now that they don't have to buy the ad725.

Looking forward for more pictures!

-Uze