E1.31, Pixelnet, DMX, Universes, Channels, etc EXPLAINED

[bob ginn]

Could someone PLEASE explain, in layman's language, the advantages/differences/compatibility/etc of these protocols(?)...for example, I know (I think) E1.31 is somehow connected to Pixelnet; some protocols have 512 channels, some 510, 2000+, 4000+, some have universes, there might even be galaxies involved that I an unaware of    There are things I (think) I understand, but for simplicity, start with the basics; any references to hardware/software should be unbiased and honest...I want to know the good and the bad, right and wrong, easy and hard, pricey and economical

TYVM (thank you very much) in advance for your input

[Charl Marais]

Hi,

a quick glance at your question seems you are mixing up a few things and while my explanation might not be 100% technically correct I hope at least it sheds some light on your confusion.

DMX is the base control method used by most people, it is just disguised a bit by all the various flavours.  For example E1.31 is just DMX disguised as a standard network signal so that you can transmit it via a normal home computer network.  This has a number of advantages in that it is very easy to set up and operate but one disadvantage is that there is no feedback or error correction so if something in the line of communication fails almost everything downstream also does not work and your software will not know that.

DMX uses what is called a universe which is simply a collection of maximum 512 individual channels.  This maximum figure cannot change but you can configure a universe to use any number of channels equal to or less than 512.  Since a typical RGB pixel contains 3 colours it uses 3 channels to control.  This effectively means you can put only 170 RGB pixels on a universe as you will then use 510 individual channels.

The people over at http://auschristmaslighting.com/ have some very nice reading materials that you can download on the site namely the AusChristmasLighting 101 manual .  I think you have to register to download it but it will be worth your time.

Regards
Charl

[bob ginn]

Thanks, I already read that manual, but will do so again.

I'm still confused-what exactly is "Pixelnet"?...is it just a term used by Falcon for their products, or is it a different "engine" from E1.31 or DMX?

[dpitts]

Thanks, I already read that manual, but will do so again.

I'm still confused-what exactly is "Pixelnet"?...is it just a term used by Falcon for their products, or is it a different "engine" from E1.31 or DMX?

DMX as stated has 512 bytes of data. The most used transport of the DMX stream was RS485 differential signaling over one pair in a cat5 cable. The speed of the signal was 250Kbps. RJ of DIYLightAnimation.com (DLA) increase the speed of DMX to 1Mbps, remove extra overhead in the DMX stream and increased the universe size to 4096 and sent four streams of this new format down a single cat5 wire. The new format was called Pixelnet. FalconChristmas just used this new format created by RJ.

[sean]

Pixelnet is another protocol for sending data out a serial cable. It has advantages of speed, disadvantages of being proprietary to one group.

Robert Jordan, who owns the DLA website, created the Pixelnet protocol for his hardware. over the last 6-7 years RJ has created dozens of christmas specific controllers, hubs, floods, ac controllers.
http://diylightanimation.com/index.php

Here is a post he made describing pixelnet
http://diylightanimation.com/index.php?topic=5174.0

So it used to be that only on the DLA site would you see Pixelnet. In the beginning of 2013 Dave Pitts and Mykroft created the Falcon-16. This had similar functionality as the DLA Zeus board. RJ did not want users of DLA equipment to be confused by having two things offered on his site that do the same function. Dave and Mykrift then created the falconchristmas.com website.

Dave has continued to develop hardware that uses Pixelnet as its protocol. So there are now two places to get hardware that uses pixelnet.
DLA
falconchristmas

They have no connection to each other.


I use dave's hardware because of Dave. Great guy and a person who does'nt make even one dollar on his hardware. He lives less than 1 hour from my home. i have suggested that he at least raise the price of his stuff by $5 or so to cover some of his costs. Dave is a big proponent of the technical advantages of pixelnet.

So you will see San Devices E682. This controller has the most string types of any controller.
J1sys p12r, p12s. 12 string controllers.

These two are used by lots of people. Greate hardware, great support

Then you come to pixelnet hardware
DLA etherdongle. E1.31 => 16K channels of pixelnet
Falcon  FPD. Raspberry Pi input via a ribbon cable => 32K channels of pixelnet out

and pixelnet hubs
DLA Active and passive hubs. 16 strings each


There are more controllers that do rgb smart strings.
the px1 is Renard in => drive one string of smart strings.

there are pros and cons for each controller. someday i hope to build a matrix to try and make this stuff easier to digest.

people get real passionate about the hardware they use.

One Caution!!
Please do NOT make personal comments about people or other forums. I want this forum to stay focused on how to get lights to blink.

[bob ginn]

Thanks for the lengthy and thorough responses so far guys...I REALLY do appreciate it, and it IS starting to make sense! 

[Timon]

The only thing I don't like about Pixelnet is the loss of the value 170. For lights it's not a problem bit if you use a Pixelnet to DMX bridge the loss of that value can cause problems.

[JonB256]

The only thing I don't like about Pixelnet is the loss of the value 170. For lights it's not a problem bit if you use a Pixelnet to DMX bridge the loss of that value can cause problems.

If the person writing the Firmware for a Pixelnet to DMX bridge doesn't compensate for the "170" value, I could see the problem. Otherwise, you just duplicate 171 or 169 into that spot and it should be a non-issue.

[Timon]

If the person writing the Firmware for a Pixelnet to DMX bridge doesn't compensate for the "170" value, I could see the problem. Otherwise, you just duplicate 171 or 169 into that spot and it should be a non-issue.

I understand that however you could have problems with any DMX device that uses some of the channels for device control. Moving head lights are an example. Again, not a problem for just illumination data just for control. Basically don't use a Pixelnet to DMX converter for connecting any DMX devices that requires control information to the bit level.

I never really understood why RJ didn't continue to use the Break as DMX does to sync as there is plenty of time to do it.

Oh well, it is what it is, it works very well and as long as you watch out for the one gotcha your fine.

[ronp]

Pixelnet does not support the break, since it uses a standard UART to output the data.

This standard UART is compatible with thousands of processors. Adding the break, makes it incompatible with the UART and makes it harder for people to expand the hardware.

[gerry]

Thanks for the explanation Sean . Coming in late , I wondered what exactly Pixelnet was too. I will add some of this posts to the manual(s) and Wiki.

[AussiePhil]

Maybe of interest to some history buffs, Pixelnet is somewhat of a marriage of HyperDMX and Renard Serial.

HyperDMX exists in some J1Sys products and it encompasses sending Standard DMX at 1Mbs allowing 4 universes to be sent out on the line at the same time. Receivers need to know how many universes are being sent though.
Renard protocol also drops a value to enable syncing

Both existed prior to Pixelnet coming out.

[neil]

just to throw something else into the mix. The PRO lighting people have been using DMX for along time and they also decided to use ARTNET which is DMX over ethernet. The take up of E1.31 (SACN) was not as great as they already have something that can do most of the work. Some controllers that we have in our hobby also support ARTNET, especially the controllers where they were approached by users who wanted to operate on ARTNET. The PRO world are also big proponents of RDM which allows for control of the devices setting remotely.