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 Post subject: Re: gscartsw: automatic 8:1 SCART-RGB switch
PostPosted: Mon Jul 21, 2014 1:49 am 



Joined: 04 Apr 2014
Posts: 376
IMO 3.5 is the only way to go. As you said, simple is best. One can always use adapters from there.

Would it reduce costs to not include a scart cable? Maybe you don't need to include one with every order. I could be wrong but I would think probably half of us use scart to bnc cables and already have them ready.


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 Post subject: Re: gscartsw: automatic 8:1 SCART-RGB switch
PostPosted: Mon Jul 21, 2014 1:55 am 


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Taiyaki wrote:
IMO 3.5 is the only way to go. As you said, simple is best. One can always use adapters from there.

Would it reduce costs to not include a scart cable? Maybe you don't need to include one with every order. I could be wrong but I would think probably half of us use scart to bnc cables and already have them ready.

I still need to do math, will do it once I will have boards here. Roughly what I saved on components was spent on board assembly so base price is the same. However I still have to solder SCARTs and other plastic components myself.
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 Post subject: Re: gscartsw: automatic 8:1 SCART-RGB switch
PostPosted: Mon Jul 21, 2014 9:56 am 



Joined: 26 Jan 2005
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Location: Bedford, UK
So your considering a 3.5 jack? Good on you.. well done!!!
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 Post subject: Re: gscartsw: automatic 8:1 SCART-RGB switch
PostPosted: Mon Jul 21, 2014 10:31 am 



Joined: 21 Jul 2014
Posts: 56
Location: UK
BuckoA51 wrote:
If anyone in the UK wants one of these next batch I will pay your shipping costs if you let me borrow it for a few days to review.


I'd be interested in taking you up on this :D


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 Post subject: Re: gscartsw: automatic 8:1 SCART-RGB switch
PostPosted: Mon Jul 21, 2014 9:07 pm 



Joined: 07 Jan 2014
Posts: 65
Put me down on the waiting list.
I want one of these for sure.

Out of curiosity, are these daisy chainable?
I may need to add a second by the end of the year.


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 Post subject: Re: gscartsw: automatic 8:1 SCART-RGB switch
PostPosted: Mon Jul 21, 2014 10:08 pm 


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sazyario wrote:
Put me down on the waiting list.
I want one of these for sure.

Out of curiosity, are these daisy chainable?
I may need to add a second by the end of the year.

Added to list.
Yes, daisy-chaining will work.
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 Post subject: Re: gscartsw: automatic 8:1 SCART-RGB switch
PostPosted: Tue Jul 22, 2014 2:22 am 


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neorichieb1971 wrote:
So your considering a 3.5 jack? Good on you.. well done!!!

I didn't said that :P.
Everything is based on demand. 4 people want JP21, 2 people - Mini-DIN->MiniDIN in addition to output SCART, and 2 more want some external audio option. It's difficult to please everybody. Also if I will start adding just random output connectors of different types it'll increase switch price, and majority of users will not like it. All of this can be implemented relatively easy through output SCART.
I write down every proposal here but currently majority of people are happy with switch as it is now, and I really don't want to do yet one more redesign, too much revisions etc.
Sorry.
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 Post subject: Re: gscartsw: automatic 8:1 SCART-RGB switch
PostPosted: Tue Jul 22, 2014 6:35 am 



Joined: 21 Jul 2014
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Location: UK
Definite UK order here. Not sure if BuckoA51 still wants one for review, but I'll order one either way.

Could you add me to the list please superg?


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 Post subject: Re: gscartsw: automatic 8:1 SCART-RGB switch
PostPosted: Tue Jul 22, 2014 11:32 am 



Joined: 26 Jan 2005
Posts: 7043
Location: Bedford, UK
So is there a one stop place to buy scart leads then? quality ones?

Some of my scarts hum through the audio.
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 Post subject: Re: gscartsw: automatic 8:1 SCART-RGB switch
PostPosted: Tue Jul 22, 2014 11:46 am 



Joined: 07 Aug 2006
Posts: 469
Location: Sydney, Australia
superg wrote:
Yeah, I know this. According to standard I shouldn't drain power from pin 8 but it's very convenient not to have external power supply and there aren't a lot of official cables now. Next version will have integrated DC jack on PCB (now it's floating cable which goes to board through SCART connector, not very handy but at least some compatibility). Another nice use-case with power over pin 8 is daisy chaining with only one external power supply. So simply it supports external power only on first switch link in daisy chain, and not relying on pin 8 or power from pin 8 from unofficial cables and IMO it's best compromise, user will decide what's best for him.

Also I would like to mention, that switch is almost transparent in terms of power consumption. If not lm1881 (which consumes up to 10mA), it consumes around 1mA. But I agree that having lm1881 on board is a good idea.


Fair enough. However, this brings up another point. As I read that I thought to myself it's impossible - how can anybody drive four video lines with only 1mA? Then I read some posts on your other thread an realised how it works.

What you have built here is an automatic passive video switcher. The is not how video switch boxes are normally made. The conventional way is to terminate the video (at 75 ohms), use a CMOS multiplexer to switch between channels with a buffer amplifier on the output with 2x gain to drive the output. The on resistance of the multiplexer not very important now so you can use cheap switches like the SN74LV4053. But that's not the biggest advantage of this method.

The problem with the passive switch is that parasitic properties of the video cables get worse with the length. The quality of SCART cables is generally not good, but it's generally not a big problem if the cable lengths are kept below 2 metres. If you plug a game consoles into two passive SCART switches daisy chained from a with 1.5m long SCART interconnects you will have a 5m long transmission line of poorly defined impedance.

superg wrote:
viletim wrote:
-For production volumes you can buy connectors directly from the connector factory. The prices are much lower than distributors and they can make them in any colour you like.

It's definitely nice suggestion, however I still need to figure out a demand for such a switch. I have no idea how many units I will be able to sell at all, and it's a bit risky to invest bigger amount of money for SCART sockets without knowing whether I will sell them all.


Oh yes, of course. I just meant to point out that the price of consumer electronics connectors may be lower than you expect. For example, you could buy 1000 pcs of good quality Taiwan made SCART connectors for US$210 from 4uconnector.com according to the currently listed prices. This way you can get the specific kind of connector you want (including colour!), rather than whatever the distributor feels like stocking.

superg wrote:
viletim wrote:
-It's a good idea to have both the mini-DIN8 and SCART connectors for output. Making special cables is no fun.

Yeah, but with MiniDIN I still need to solder the other end myself (being it SCART or another MiniDIN). I think I will use same straight SCART for output and by default I will provide SCART->SCART cable (which is standard, I will just need to find inexpensive source of them)
And as an option I will offer SCART->MiniDIN. BTW: where can I buy MiniDIN cable assembly like the one you're using in your NESRGB kit?
(digikey has this one: http://www.digikey.com/product-detail/e ... ND/2625275, but I think it's too thick and expensive also)


When I last looked I didn't find anything suitable from my usual wholesalers. The 8 pin mini DIN cables that I did find were old Apple Mac printer cables that have some wires crossed over. The cables I sell in my shop are made for me by a small cable factory in China.


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 Post subject: Re: gscartsw: automatic 8:1 SCART-RGB switch
PostPosted: Tue Jul 22, 2014 4:49 pm 



Joined: 04 Apr 2014
Posts: 376
viletim wrote:
The problem with the passive switch is that parasitic properties of the video cables get worse with the length. The quality of SCART cables is generally not good, but it's generally not a big problem if the cable lengths are kept below 2 metres. If you plug a game consoles into two passive SCART switches daisy chained from a with 1.5m long SCART interconnects you will have a 5m long transmission line of poorly defined impedance.


Do you mean picture integrity can be roughly measured by the length of the output cable + cable connecting the console to the box? In that case I'm pretty sure most will have 2m or more even without daisychaining.

Would connecting the power supply remedy this?


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 Post subject: Re: gscartsw: automatic 8:1 SCART-RGB switch
PostPosted: Tue Jul 22, 2014 9:07 pm 



Joined: 09 Mar 2011
Posts: 647
Have you ever tried using a non-powered VGA switchbox, e.g. a dumb N-way switch?
You notice the picture degrades really bad, you get ghosting, blurring, etc? Well... that's basically what will happen
unless you have a proper powered buffering amp circuit as mentioned above. Plugging in a power source
isn't going to help here since it will only power the auto-switching part.


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 Post subject: Re: gscartsw: automatic 8:1 SCART-RGB switch
PostPosted: Tue Jul 22, 2014 9:17 pm 


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alamone wrote:
Have you ever tried using a non-powered VGA switchbox, e.g. a dumb N-way switch?
You notice the picture degrades really bad, you get ghosting, blurring, etc? Well... that's basically what will happen
unless you have a proper powered buffering amp circuit as mentioned above. Plugging in a power source
isn't going to help here since it will only power the auto-switching part.

Not quite.
What viletim said is true, but such degradation is very relative. Few people here are using daisy-chaining with 2 switches and by default I supply 5ft cables (I use higher quality multi-thread acoustics cable for MiniDIN->SCART). So according to their and my testing it was still fine (and for my tests I used 3 switches sequentially and total cable length was 15ft). Don't forget that TV/XRGB has an internal amplifier inside.
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 Post subject: Re: gscartsw: automatic 8:1 SCART-RGB switch
PostPosted: Wed Jul 23, 2014 1:13 am 


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viletim wrote:
Fair enough. However, this brings up another point. As I read that I thought to myself it's impossible - how can anybody drive four video lines with only 1mA? Then I read some posts on your other thread an realised how it works.

What you have built here is an automatic passive video switcher. The is not how video switch boxes are normally made. The conventional way is to terminate the video (at 75 ohms), use a CMOS multiplexer to switch between channels with a buffer amplifier on the output with 2x gain to drive the output. The on resistance of the multiplexer not very important now so you can use cheap switches like the SN74LV4053. But that's not the biggest advantage of this method.

The problem with the passive switch is that parasitic properties of the video cables get worse with the length. The quality of SCART cables is generally not good, but it's generally not a big problem if the cable lengths are kept below 2 metres. If you plug a game consoles into two passive SCART switches daisy chained from a with 1.5m long SCART interconnects you will have a 5m long transmission line of poorly defined impedance.

Agree, so much effort not to use external power supply. As I've said in my previous post, I tested 3 switches in sequential chain and wasn't able to notice any difference. And in real life there should be only 2 levels in hierarchy (parallel connection and not sequential), I doubt anybody will have more than 64 devices :).
Well, to be honest now I don't know what would be best solution. After all maybe relying solely on the power supply is not as bad idea as I thought initially.
Anyway I got PCB batch today, everything works perfectly, and now all official cables provide enough power (tried official PSX, Xbox and Dreamcast SCART's, everything is plug and play). Still when LM1881 is turned on and official cables are used, it needs external power.

viletim wrote:
Oh yes, of course. I just meant to point out that the price of consumer electronics connectors may be lower than you expect. For example, you could buy 1000 pcs of good quality Taiwan made SCART connectors for US$210 from 4uconnector.com according to the currently listed prices. This way you can get the specific kind of connector you want (including colour!), rather than whatever the distributor feels like stocking.

Thanks for the link, I will keep that in mind!

viletim wrote:
When I last looked I didn't find anything suitable from my usual wholesalers. The 8 pin mini DIN cables that I did find were old Apple Mac printer cables that have some wires crossed over. The cables I sell in my shop are made for me by a small cable factory in China.

Oh, I've seen plenty of those crossed over on ebay.
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 Post subject: Re: gscartsw: automatic 8:1 SCART-RGB switch
PostPosted: Wed Jul 23, 2014 1:57 am 



Joined: 04 Apr 2014
Posts: 376
What scart cables use LM1881? Do any of the retro console accessories cables on ebay use it?


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 Post subject: Re: gscartsw: automatic 8:1 SCART-RGB switch
PostPosted: Wed Jul 23, 2014 2:01 am 


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Taiyaki wrote:
What scart cables use LM1881? Do any of the retro console accessories cables on ebay use it?

I've seen somewhere SMD2 cable with integrated lm1881.
I need LM1881 only for my Mega Drive 2. Other people reported that they needed it also for some other consoles.
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 Post subject: Re: gscartsw: automatic 8:1 SCART-RGB switch
PostPosted: Wed Jul 23, 2014 3:19 am 



Joined: 17 Sep 2012
Posts: 393
Taiyaki wrote:
What scart cables use LM1881? Do any of the retro console accessories cables on ebay use it?


Depending on where you buy cables, they're labeled as "sync-strippers" or "sync-cleaners". Retro Console Accessories (Retro Accessories on the forum) labels them as sync-strippers.


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 Post subject: Re: gscartsw: automatic 8:1 SCART-RGB switch
PostPosted: Wed Jul 23, 2014 4:41 am 



Joined: 04 Apr 2014
Posts: 376
Can I assume that since those made by Retro Accessories are not official cables they work without needing power?


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 Post subject: Re: gscartsw: automatic 8:1 SCART-RGB switch
PostPosted: Wed Jul 23, 2014 5:02 am 



Joined: 17 Sep 2012
Posts: 393
Taiyaki wrote:
Can I assume that since those made by Retro Accessories are not official cables they work without needing power?


Correct, it gets power from the +5v line provided by the console.

And to be clear, the LM1881 circuit is normally in the XRGB mini adapters she sells. The circuit isn't in the cable she sells normally. I think the some of the Genesis cables are the exception though.


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 Post subject: Re: gscartsw: automatic 8:1 SCART-RGB switch
PostPosted: Thu Jul 24, 2014 4:37 am 



Joined: 04 Apr 2014
Posts: 376
Thank you, that makes sense.

Would installing the LED on the nesrgb scart by Tim make it so the gscartsw would require additional power?

http://etim.net.au/cable-adapter/scart- ... -guide.htm


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 Post subject: Re: gscartsw: automatic 8:1 SCART-RGB switch
PostPosted: Thu Jul 24, 2014 3:48 pm 



Joined: 19 Jul 2013
Posts: 265
Taiyaki wrote:
Thank you, that makes sense.

Would installing the LED on the nesrgb scart by Tim make it so the gscartsw would require additional power?

http://etim.net.au/cable-adapter/scart- ... -guide.htm

what is that?


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 Post subject: Re: gscartsw: automatic 8:1 SCART-RGB switch
PostPosted: Thu Jul 24, 2014 3:55 pm 



Joined: 04 Apr 2014
Posts: 376
EmperorZelos wrote:
Taiyaki wrote:
Thank you, that makes sense.

Would installing the LED on the nesrgb scart by Tim make it so the gscartsw would require additional power?

http://etim.net.au/cable-adapter/scart- ... -guide.htm

what is that?


That's the Scart cable for the NES made by Tim, the same person who made the nesrgb. I was wondering whether it wouldn't be better not to install the LED in order to have it running without power on the gscartsw.


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 Post subject: Re: gscartsw: automatic 8:1 SCART-RGB switch
PostPosted: Thu Jul 24, 2014 4:18 pm 


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delete


Last edited by mickcris on Thu Jul 24, 2014 5:04 pm, edited 1 time in total.

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 Post subject: Re: gscartsw: automatic 8:1 SCART-RGB switch
PostPosted: Thu Jul 24, 2014 4:43 pm 


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Taiyaki wrote:
EmperorZelos wrote:
Taiyaki wrote:
Thank you, that makes sense.

Would installing the LED on the nesrgb scart by Tim make it so the gscartsw would require additional power?

http://etim.net.au/cable-adapter/scart- ... -guide.htm

what is that?


That's the Scart cable for the NES made by Tim, the same person who made the nesrgb. I was wondering whether it wouldn't be better not to install the LED in order to have it running without power on the gscartsw.

It should be just fine.
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 Post subject: Re: gscartsw: automatic 8:1 SCART-RGB switch
PostPosted: Thu Jul 24, 2014 8:51 pm 


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superg wrote:
Taiyaki wrote:
How many will be stocked? Should we start preordering?

For now it's only 10 switches.
I will add you to my queue if you want.
I am not ready to pay for big quantities, so most likely it'll go 10-20 every batch.
But further batches will go faster if I will not need any changes.


Oh cool, this is moving along. :)

Is my name early enough in the queue for one of these next 10? :o


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 Post subject: Re: gscartsw: automatic 8:1 SCART-RGB switch
PostPosted: Sat Jul 26, 2014 7:36 pm 


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Forks wrote:
Oh cool, this is moving along. :)

Is my name early enough in the queue for one of these next 10? :o

You're almost in the top of list, absolutely you'll get one this batch.
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 Post subject: Re: gscartsw: automatic 8:1 SCART-RGB switch
PostPosted: Sat Jul 26, 2014 7:37 pm 


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Also, I think I will be able to implement JP21 :)
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 Post subject: Re: gscartsw: automatic 8:1 SCART-RGB switch
PostPosted: Sat Jul 26, 2014 11:18 pm 


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Quote:
Not sure if BuckoA51 still wants one for review, but I'll order one either way.


I do, drop me a PM and we'll work out the specifics.
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 Post subject: Re: gscartsw: automatic 8:1 SCART-RGB switch
PostPosted: Thu Aug 07, 2014 3:59 am 


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A little update.
Here's how new switch looks:
Image
Image

Just did some chaining:
Image

My Sega Genesis connected through 4 switches sequentially, no visible degradation. 5ft Genesis SCART cable + 4 * 4ft switch-switch SCART cable, which is 21ft in total.
I was able to see some degradation starting from 5 switches in chain.
However there is no any reason for having more than 2 switches in daisy chain, it should grow in breath first order so you may clearly have 8 switches (64 input ports) connected to 9th root one.
I am still waiting for silicon pads and hopefully on this weekend I'll finish testing and check pricing.

FYI: here's main development thread:
http://www.assemblergames.com/forums/sh ... RT-project
A lot of information is scattered around, just skim through these topics, there are a lot of information on the switch.
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 Post subject: Re: gscartsw: automatic 8:1 SCART-RGB switch
PostPosted: Sat Aug 09, 2014 5:30 pm 


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FYI: I've just updated topic with actual information and photos.
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