S-Video Crosspoint Router Project

I am at the dirt kicking and head scratching phase of starting a new project. I have been wanting to do something about the wiring mess behind my HT system and the only commercially available routers are either too limited or else are broadcast gear and cost mucho dinero. The main reason for going down this path is I want to be able to be able to switch my video processing box to different applications (DVD to VCR) or (VCR to TV) or (VCR to second VCR) without having to be constantly plugging and unplugging cables.

My system has the following configurations:

S-Video inputs
1: From Cable Box
2: From DVD Player
3: From VCR Out
4: From Video Processor Out

S-Video Outputs
1: To TV
2: To Video Processor Input
3: To VCR Input
4: To Second VCR Input

That way I can patch signals through the router multiple times if needed. Here is a routing example:

DVD to Processor In
Processor Out to VCR In
VCR Out to TV In

This way I can monitor the recording process from the TV, and if something comes up that I want to watch on cable, I can switch the TV to that without disturbing the recording process or swapping any cables.

I was thinking that a 4x4 S-Video cross point router project based on the MAX-456 8x8 crosspoint router chip would do what I want. This chip includes channel buffers so any input can go to any combination of outputs. The chip does require buffer amps to be able to drive 75 ohm cables however.

I plan on using an 87C52 processor to handle the user interface and to control the crosspoint router chip. For power I plan on using a 12 VAC center tapped wall transformer and LM317 and LM337 regulators for the +/- 5 VDC video supplies. A 7805 would power the digital circuitry.

For the user interface I had in mind a vertical row of 4 buttons which are used to select the destination (output) and a horizontal row of 4 button used to select the source (input channel which is to connect to that output. To assign an input to an output you would first select the output channel. The current input assignment is indicated by one of the horizontal LED's being lit. To change the assignment just press one of the buttons in the horizontal row.

The internals would consist of two small PCB's. The rear PCB would contain all of the active electronics and the S-Video connectors would be mounted directly to the PCB (eliminating cables). The front PCB would contain the buttons and LEDs and connect to the rear PCB by a ribbon cable.

Comments or suggestions. This will be my first video project, but I have done quite a bit of embedded electrical/software design work with the A/D converters and '51 processors so that part will not be a problem. I welcome any suggestions about the video portion of the design. At this point I am basically planning on implementing per MAX's reference design unless someone can point me to some clever alternatives. I am open to using something other than the MAX456 if there is a better choice. I am also open to suggestions on a good choice for the buffer amps. Max has a quad buffer amp they recommend for this, but perhaps there are better choices available?

I am also considering adding an IR remote control to the box. Any ideas about the best way to do this?

I plan on etching my prototype boards, but I am considering having a prototype board house make board sets and would be willing to make them along with programmed processors available at my cost to anyone who is interested.
 

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Haldor,

Sorry no one posted. I think the problem was that you seem to have it all together. And, most of us are optic's freaks rather than circuit nuts.

The Ir part can be done using any of the circuits listed on various elec. circuit discussion groups. If you're in dire need I have one in a book somewhere that can control over 30 functions, if not more.

I can scan it in and send.

Cheers
 
Thanks,

I'd like to look at it. The lack of response was kind of daunting. Seemed like something someone besides me might be interested in, guess I was wrong. You can buy these commercially, but they are expensive ($1500 and up). The Max456 costs around $50 from Digikey and with everything else the final cost should have been under $150.

Actually after thinking further on this I can get most of the benefit of the crosspoint router with a s-video selector switch box and a distribution amp.

The selector switch would go on the input to the video processor and let me select between the signal sources (Cable converter, DVD, VRC, game console). The output of the video processor would feed the distribution amp and everything with an input (TV, VCR, etc) would get their signal from that.

Phil
 
Hi Arbury,

You are correct the MAX456 will only handle the video portion of the job. I am considering using the Mitel MT8809 for the audio switching. Haven't heard any products that use this chip (that I am aware of) so am not sure how good it's going to sound. Spec wise it looks decent. Got any good candidates to suggest?

I am also considering Analog Devices AD8108/AD8109 for the video cross point switch as an alternative to the MAX456. Need to review specs and see which one looks like it will do a better job. I like the MAX part because I2C is such a simple interface to implement and you can add on more parts without tying up processor pins.

Maxim has a lower cost alternative, the MAX4456. Not sure how much the performance would be compromised yet, needs further consideration. This part is a drop in replacement for the MAX456 so it might be interesting to try both and see if the differences are visible.

Phil
 
Haldor,

Just took a look at the MAX4456. Looks like it should work just as well as the MAX456 for everything but the most demanding applications. How much cheaper is it? I have not been able to find a price for it yet (in Canada anyway).

I was planning on making a 6 in 2 out AV crosspoint router about 6 months ago, but other things came up and I never got past the planning stage. I was going to use many 3 way switchers connected together (cannot remember which ICs they were, going to have to find my notes) to perform the switching. It was somewhat messy and without an amplifier I would have trouble sending on source to both outputs at the same time, but I was more concerned with saving money at the time.

Using the 3 way switchers was going to cost me about $100 Canadian (enough for both audio and video). The MAX456 is over $80 by itself. However, if the MAX4456 is cheap enough I may look at resurrecting this project and using it instead of the 3 way switching ICs.

The Mitel MT8809 looks good for audio, although I also have not heard anything using it.

Arbury
 
Hi Arbury,

The MAX4456 is about half the price of the MAX456. Only problem is I haven't been able to find anyone that has it in stock. Avnet lists it for around US$20, but has a minimum buy quantity of 10 pieces. If there is enough interest I might order 10 parts from AVNET, otherwise the US$50, quantity 1 price for the MAX456 from Digikey is will be the better deal for me.

I will take a look at sourcing for the AD8108/9 as well.

Cool thing about a crosspoint switch is that you can connect any or all of the outputs to any of the inputs and can reroute one portion of the system without effecting something else. This would let me watch a DVD and record a show from cable at the same time (or visa-versa). I could also jump monitor the recording process at any time without having to swap any cables around or effecting the recording.

Phil
 

bbkrause

Member
2002-06-19 6:38 pm
If you haven't already purchased the crosspoint ICs, why don't you let the manufacturer GIVE them to you as samples? I have discovered that Maxim (www.maxim-ic.com), National semiconductor (www.national.com), Analog Devices, and TI all have quite generous sampling policies. Maxim, for example, will send you two each of 5 or more different parts at a time - I requested (and received) two MAX456s and two MAX4456s as part of a single sample order. Just don't tell them I sent you!!

I have also seen the Mitel mux and have been curious about it ('cause it's cheap). I'd be interested to know about anybody's experience with it.
 
Hi bbkrause,

I know about samples. I am a design engineer by profession and I get regular visits from most of the IC vendors and distributors. I only request samples for products I am seriously considering using in a commercial product. I value the support I get from vendors too much to jerk them around for my hobby activities.

I'm not slamming anyone else for getting samples if they can, but I feel it would be unethical for me to do so since these guys will give me virtually anything I ask for (including development boards and tools).

Best swag I was ever offered was a free Hitachi SH-3 ICE that sells for around $18K. We were selecting a processor for a new product and they were trying to sweeten the pot. I ended up using an ARM based processor instead. Hitachi did have the best looking sales staff, but after a few visits we started calling them the Hitachi Babes (good looking, but not terribly knowledgable about their product).

Phil
 
Hi again bkrause,

Did you ever make a project with the MAX456, MAX4456 parts? Got any comments or design suggestions? How happy where you with the performance?

If you never did anything with the samples would you be willing to part with one? I'd be most obliged since it would save me from chasing down a part.

Phil
 

bbkrause

Member
2002-06-19 6:38 pm
Thanks for your ethics comments. I'll have to rethink mine since I've retired from the corporate world.

I haven't built anything with the 456 or 4456 as yet. My project is a video switcher somewhat similar to yours. I'll build two for the church I attend and one for myself. As to control I considered a pic or the like, but am now looking at the ZWorld RabbitCore 3000 line of boards. One of these will set me back a bit over 50 bucks and will provide network connectivity (10BaseT) and plenty of horsepower and ports to handle all of the keyboard, status, IR I/O with plenty left over to control some audio stuff which I'd also like to implement.

Send you a part? Sure, why not. Which do you prefer, 456 or 4456? Makes no difference to me - it looks like they'll both perform identically for our application. If I end up short a chip, and if I end up changing my ethical stance, then another one will set me back a few bucks, but it'll be well worth the ethical counsel you offered. I'll need an address.