An illustration of Smart String Layout

[ptone]

Here is an illustration and some notes about my understanding of smart string layout.  Corrections welcome, but hopefully this will help clarify how this works for some.  I'm keeping this updated with improvements and corrections in an effort to improve the understanding of those trying to learn - constructive criticism welcome.



Wiki information on PixelNet:
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PixelNet Universe = 4096 Channels =~ 1365 Nodes (R,G,B channels per node)
128 nodes per string (Max) = 384 Channels
1 Hub = 16 SSC = 6144 Channles which is > 1 PixelNet univers, so not possible to saturate a hub.
1 PixelNet Universe might support:

• 1 hub, 16 strings of 85 nodes each = 4080 channels
• 2 hubs, 5 strings of 100 (1500ch) in 1 hub and 16 strings of 50 (2592ch) in another hub for a total of 4092ch
• 8 hubs with 10 strings each of 17 nodes = 4080ch

Note that these numbers are illustrative and do NOT account for hybrid mode channels.  But they help illustrate the basic idea of what quantity a PixelNet Universe is.

1 new dongle supporting 16K channels, will support 4 PixelNet universe with single Cat5 output. 1 universe for each pair of the Cat5.

[rrowan]

Hi Ptone

I am not sure you got it all correct.

Example: You should not combine DMX and Pixnet. ie: 384 Channels = 1 DMX Universe per SSC.


Plus RJ created basic diagrams in the What is a smart string topic. I copied the diagrams to the wiki for easy lookup later.

Rick R.

[ptone]

Rick,

I've clarified that bit in the original - they are mixed, as RJ has stated that the SSC takes PixelNet as in input, and outputs DMX.  So PixelNet can be seen as a Protocol for "packing" multiple (partial) DMX universes into one serial stream.  This will be useful from a software point of view and a familiarity point of view where lights and channels are assumed to live in DMX universes.  Another angle on this, if there were no power limitations on a string, then the max number of nodes would probably be 170, as the limit of 512 DMX channels per string would then kick in.

My point of doing a new illustration is that there continues to be much confusion about hubs and ssc layout, so I figured another angle couldn't hurt.  Also the "what is a SS" thread is so massive - many are no longer bothering to wade through it.

-P

[rrowan]

The Pixelnet is the (converted) dongle, hub, SSC at the moment.
The hub can take up to 512 channels from the pixelnet to be use for DMX devices we already have. The hub has one dmx output rj-45. The other 16 rj-45 is still pixelnet.

RJ45 Connectors is a total of 19 on the HUB
1 - Pixelnet Input
1 - Pixelnet Output (daisy chain to other Hubs)
16 - Outputs for the SSCs
1 - DMX output

Rick R.

[tbone321]

Rick,

I've clarified that bit in the original - they are mixed, as RJ has stated that the SSC takes PixelNet as in input, and outputs DMX.  So PixelNet can be seen as a Protocol for "packing" multiple (partial) DMX universes into one serial stream.  This will be useful from a software point of view and a familiarity point of view where lights and channels are assumed to live in DMX universes.  Another angle on this, if there were no power limitations on a string, then the max number of nodes would probably be 170, as the limit of 512 DMX channels per string would then kick in.

Where exactly did you see RJ state that the SC converts pixelnet to DMX?  Early in the "what is pixelnet" thread he indicated that the SSC does not use DMX and is free of the 170 node DMX break penalty.  

My point of doing a new illustration is that there continues to be much confusion about hubs and ssc layout, so I figured another angle couldn't hurt.  Also the "what is a SS" thread is so massive - many are no longer bothering to wade through it.

-P

While the illustration you provided is nice, it is a bit misleading and innaccurate.  You are showing a single 12V source powering all of the hubs and altough you may be able to do that, it is not the recommended method and may be misleading.  You are also showing the upper two hubs being controlled by seperate Lynx dongles.  That would only be needed if each hub is on a seperate pixelnet universe.  The hubs can be daisy chained if on the same universe using the Lynx dongle and you should show that.  You are also showing a pixelnet dongle seperatly connecting to the bottom two hubs and that is incorrect.  The pixelnet dongle connects to the first hub and the rest daisy chain from the first.  The universe that any hub is working with is selected by jumpers on the hub and all 4 universes are passed along the line so the order of the hubs in the chain has nothing to do with the universe it is working wth.

[ptone]

Rick,

I've clarified that bit in the original - they are mixed, as RJ has stated that the SSC takes PixelNet as in input, and outputs DMX.  So PixelNet can be seen as a Protocol for "packing" multiple (partial) DMX universes into one serial stream.  This will be useful from a software point of view and a familiarity point of view where lights and channels are assumed to live in DMX universes.  Another angle on this, if there were no power limitations on a string, then the max number of nodes would probably be 170, as the limit of 512 DMX channels per string would then kick in.

Where exactly did you see RJ state that the SC converts pixelnet to DMX?  Early in the "what is pixelnet" thread he indicated that the SSC does not use DMX and is free of the 170 node DMX break penalty.  

The SSC does not use (consume) DMX, it consumes PixelNet, and my understanding is it outputs DMX from this comment:
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My point of doing a new illustration is that there continues to be much confusion about hubs and ssc layout, so I figured another angle couldn't hurt.  Also the "what is a SS" thread is so massive - many are no longer bothering to wade through it.

-P

While the illustration you provided is nice, it is a bit misleading and innaccurate.  You are showing a single 12V source powering all of the hubs and altough you may be able to do that, it is not the recommended method and may be misleading.  

While I did this initially to reduce clutter and had a note about it being schematic, I agree and have made the change.

You are also showing the upper two hubs being controlled by seperate Lynx dongles.  That would only be needed if each hub is on a seperate pixelnet universe.  The hubs can be daisy chained if on the same universe using the Lynx dongle and you should show that.

I did show this with the new dongle - however I also wanted to point out that you COULD use 2 USB dongles, I've added an extra hub to one of them to show that permutation.

 You are also showing a pixelnet dongle seperatly connecting to the bottom two hubs and that is incorrect.  The pixelnet dongle connects to the first hub and the rest daisy chain from the first.  The universe that any hub is working with is selected by jumpers on the hub and all 4 universes are passed along the line so the order of the hubs in the chain has nothing to do with the universe it is working wth.

Where is this outlined or explained?  My understanding from reading the PixelNet spec, is that it is limited to 1 PixelNet Universe on the wire.  Having 4 PixelNet universes on one RS-485 line would reduce the update rate.  Also the new dongle has been referred to as having 16K channels, which is much more than 4 PixelNet Universes.

-P

[tbone321]

Where is this outlined or explained?  My understanding from reading the PixelNet spec, is that it is limited to 1 PixelNet Universe on the wire.  Having 4 PixelNet universes on one RS-485 line would reduce the update rate.  Also the new dongle has been referred to as having 16K channels, which is much more than 4 PixelNet Universes.

-P

Ok, the point that you have to remeber is that it only takes one twisted pair to make an output.  Cat 5 cable has 4 twisted pairs therefore the dongle can and will put out all four universes on one cable.  So even though the new dongle has 4 seperate outputs, they are all on the same cable on different pairs.  If you look in the wiki at the picture of the hub you will see there are jumpers on the hub to tell it what universe or pair of wires to get the signal from.  As for the channel count, the dongle puts out 4 pixlenet universes of 4096 channels each and the last time that I looked 4 x 4000 = 16000 although with my last attempt at math last night that may be in question.   

[tbone321]

The SSC does not use (consume) DMX, it consumes PixelNet, and my understanding is it outputs DMX from this comment:
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That is not what he was talking about.  He was refering to the hub that has a pick that is used to output a DMX universe.  If you look at the picture of the hub on the wiki you will see the DMX output jack as well as a jumper that allows you to select a DMX universe althouh I'm not sure what exactly what that jumper does.

[RJ]

Where is this outlined or explained?  My understanding from reading the PixelNet spec, is that it is limited to 1 PixelNet Universe on the wire.  Having 4 PixelNet universes on one RS-485 line would reduce the update rate.  Also the new dongle has been referred to as having 16K channels, which is much more than 4 PixelNet Universes.

-P

Why that would be right here :

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Page 6 of the documentation shows that each pair carries a seperate Pixelnet Universe on the final setup.

Another angle on this, if there were no power limitations on a string, then the max number of nodes would probably be 170, as the limit of 512 DMX channels per string would then kick in.

Actually it has nothing to do with DMX. Pixel net is not based on 512 it is just 4096 channels of data. Now of course we can get 8 DMX universe to fit inside of it but it is not really based on DMX.

Presumably the new dongle will have multiple outputs to support the higher number of channels.

This is not correct the new dongle designed for 16384 channels will be one Cat5 output but 4 universes of PixelNet on that wire.

So there was a little bit of confusion but not too much.

The documents do cover this it is just new stuff so it takes a little while to sink in. In the big picture when it hits you it is very simple.

RJ

[ptone]

Duh - I read that doc, but obviously not carefully to the end.  Shame on me!  Also duh on the 4x4K=16K bit 

The top post has been updated with all existing input and feedback.

Still some confusion about what the protocol is downstream of the SSC, is it DMX or not?

-P

[tbone321]

Does it really matter what the protocol is downstream of the SSC?  I do know that it is not DMX and since the SSC is dedicated and actually part of the smartstring, I personally don't care.  As long as it controls the string properly I'm happy.

[rrowan]

Duh - I read that doc, but obviously not carefully to the end.  Shame on me!  Also duh on the 4x4K=16K bit 

The top post has been updated with all existing input and feedback.

Still some confusion about what the protocol is downstream of the SSC, is it DMX or not?

-P

SSC reads pixelnet data, the hub is needed to inject power along with resending the pixelnet data to each ssc and to the next hub if its connect

Rick R.

[ptone]

The SSC does not use (consume) DMX, it consumes PixelNet, and my understanding is it outputs DMX from this comment:
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That is not what he was talking about.  He was refering to the hub that has a pick that is used to output a DMX universe.  If you look at the picture of the hub on the wiki you will see the DMX output jack as well as a jumper that allows you to select a DMX universe althouh I'm not sure what exactly what that jumper does.

I guess that was ambiguous and I may have made the wrong conclusion.  The post being replied to asked if there was a Pic in the SSC and/or Hub.  I'm assuming that the DMX out jumper on the Hub is the start channel of pixelnet that gets converted to DMX.  So <jumper> x 512 or something along those lines.

The output and protocol on the SS downstream of the SSC I guess is still a mystery, I had thought that post implied DMX, but then in other documents it sounds something more analogous to renard, as each node pops off values and passes on the rest.

-P

[ptone]

Does it really matter what the protocol is downstream of the SSC?  I do know that it is not DMX and since the SSC is dedicated and actually part of the smartstring, I personally don't care.  As long as it controls the string properly I'm happy.

It doesn't matter - it is only because I'm a professional scientist by training that I'm curious about the entirety of the system.  If it is to remain a secret, or just unexplained, I have no qualms with that.

-P

[tbone321]

I understand that and I think that Rick explained it a just pixelnet data.  The SSC just sends what is needed down the string depending on how you configured it and the nodes probably just react to the first three channels they see and pass the rest on down the line as you suggested.