Author Topic: WS2813 or WS2818 pixels?  (Read 1133 times)

Offline danj

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WS2813 or WS2818 pixels?
« on: December 27, 2018, 07:02:33 PM »
I have dug around a bit and found a few older posts (about 2 years ago) on this forum about WS2813/WS2818 pixels that don't take down the "rest" of a strand when a pixel dies, but none since that timeframe.  Any idea if the F16V3 can drive either or both of these protocols?  Has anyone used these in their displays?   I have all WS2811's right now and would like to start purchasing pixels that don't take down the rest of a strand if just one pixel dies.  Of course, I plan to continue to use all Falcon hardware...   So "usability" of these pixels with a Falcon controller (I am using F16V3s) is important to me.   TIA!

Offline jnealand

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Re: WS2813 or WS2818 pixels?
« Reply #1 on: December 27, 2018, 07:32:19 PM »
What I recall is that those are just 2811s with other smarts built into the chips inside pixels so I would not think there was anything to be done in a controller for those.  Also what I recall is that they pass on the signal as though the pixels were lit up without regard if they are really working.  That being said if the whole node burns out I doubt that will help you.   Maybe, but I will wait to see if they really work before putting money in them.  Most of the problems I see are a single color going out in a pixel and not a whole long line going out.  I have seen that too, just not very often.
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Offline pixelpuppy

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Re: WS2813 or WS2818 pixels?
« Reply #2 on: December 27, 2018, 08:11:29 PM »
I have a strip of 2813s I got to test and experiment with.    They use 2811 protocol as far as the controller is concerned.    The backup data line goes around each pixel, so even if the whole chip dies the backup/bypass function still works.


Its a very easy swap that requires no controller or programming changes.   Im hoping these will become more mainstream in 2019 and I intend to migrate to them
-Mark

Offline danj

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Re: WS2813 or WS2818 pixels?
« Reply #3 on: December 27, 2018, 08:18:58 PM »
Thanks for the replies gentlemen!   This is what I read--that essentially there is a "backup data" wire, making these 4 wire instead of 3.   For the ones that you used, did you just put the "normal" data wire AND the "backup" data wire into the signal ports on the controller?   I was thinking it <should be> that simple....    Thanks again.

Offline pixelpuppy

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Re: WS2813 or WS2818 pixels?
« Reply #4 on: December 27, 2018, 08:53:21 PM »
you only use 3 wires from controller to 1st pixel.  The 4th backup data wire is only needed between pixels

Offline tbone321

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Re: WS2813 or WS2818 pixels?
« Reply #5 on: December 30, 2018, 02:17:22 AM »
While this sounds like a great idea, these dual input chips are going to increase the cost of the nodes.  If they become competitive in price to the WS8211 then I will look into them as well.

Offline pixelpuppy

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Re: WS2813 or WS2818 pixels?
« Reply #6 on: December 30, 2018, 08:50:52 AM »
While this sounds like a great idea, these dual input chips are going to increase the cost of the nodes.  If they become competitive in price to the WS8211 then I will look into them as well.

I wouldn't be surprised if World Semi (the maker of WS28xx chips) is already tooling to replace all 2811 dies with 2813 - if they haven't already.  Remember when they changed the reset timing spec on the 2811 last year?  That was done because the 2813 backup sensing requires a longer framing gap to determine when to switch to backup.   This gave controller manufacturers time to update their firmware to work interchangeably with both 2811 and 2813.   Since the 2813 without the BI input acts exactly like a 2811, I  doubt they are going to keep making two separate sets of wafers and dies.   The 2813 die can be packaged and sold as either 2811 of 2813 depending on whether they attach the BI/BO (externally to the die)

What I'm saying is the mass production cost difference is minimal - basically just the cost of one more conductor between pixels.  For marketing purposes, the same base chip can be packaged in strings as either 2811 or 2813 with the only difference being the 4th wire.  That's up to the buyer's market to decide.   The manufacturers could decide to make the two compete as a marketing ploy ('economy'/'residential' model versus 'commercial'/'pro' model) but I doubt it.   I highly suspect what we will see is the 2813 essentially replacing the 2811 for virtually the same cost.

Offline algerdes

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Re: WS2813 or WS2818 pixels?
« Reply #7 on: December 30, 2018, 09:33:32 AM »
I'm curious about one thing.  We see two different kinds of failures when it comes to string pixels.  The first, failure of the chip, would be covered by this wiring/input scheme.  When a pixel fails the next chip removes the failed chips data from the backup data stream, uses the next bit of commands and continues on.


The second, perhaps harder to detect, is the flaky malfunction of the chip.  Essentially it sends erroneous data to the following chip. This data is sometimes confused as real data and the following chips obey this new (bad) information.


In this dual data scenario, is the following chip reading both lines and comparing them to see which one to use?
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Offline jnealand

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Re: WS2813 or WS2818 pixels?
« Reply #8 on: December 30, 2018, 01:30:31 PM »
I do not understand either.  Every chip strips off its piece of data and sends the remainder on.  If a pixel dies and the data stream keeps going why aren't all following pixels three channels off.  How does one chip klnow that the preceding one is dead?  Would look kind of weird in a mega tree.  What happens if two chips in a row are dead?

Offline Bwinter

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Re: WS2813 or WS2818 pixels?
« Reply #9 on: December 30, 2018, 02:11:04 PM »
If I remember, if data is used off the back-up line, then it knows to remove one pixel (thus keeping everything in sync).

I remember a bit of a flurry on these last year too. Someone planned on going all-in.  Never heard any follow-up this year though.

To me, it seemed like an upgrade that may solve some (but not all) of the potential scenarios when a pixel goes bad.

Offline tbone321

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Re: WS2813 or WS2818 pixels?
« Reply #10 on: December 31, 2018, 08:10:51 AM »
I do not understand either.  Every chip strips off its piece of data and sends the remainder on.  If a pixel dies and the data stream keeps going why aren't all following pixels three channels off.  How does one chip klnow that the preceding one is dead?  Would look kind of weird in a mega tree.  What happens if two chips in a row are dead?


The wiring of these strips is a little weird.  Basically, how they are wired is the data input for a node is also the backup input for the following node so there is a wire connecting the backup input lead of a node to the data input lead of the previous node.  All the chip does is look at the two inputs and if it sees an input on the backup and not on the normal input, it shuts down the normal input and pulls data from the backup input and knows to strip off the first 24 bits of data before processing and reshaping the data stream so the proper channel number is maintained.  The protection only goes for a one node in a row failure but most of the time, that's exactly what happens.

Offline tbone321

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Re: WS2813 or WS2818 pixels?
« Reply #11 on: December 31, 2018, 08:23:10 AM »
I'm curious about one thing.  We see two different kinds of failures when it comes to string pixels.  The first, failure of the chip, would be covered by this wiring/input scheme.  When a pixel fails the next chip removes the failed chips data from the backup data stream, uses the next bit of commands and continues on.


The second, perhaps harder to detect, is the flaky malfunction of the chip.  Essentially it sends erroneous data to the following chip. This data is sometimes confused as real data and the following chips obey this new (bad) information.


In this dual data scenario, is the following chip reading both lines and comparing them to see which one to use?


No, it does not have that type of ability.  It simply looks at the two data lines and falls back to the backup line if there is no data on the normal input.  As a plus, once it falls back to the backup data line, it continues to use just the backup data line until it is reset by power cycle so if your corrupt data line is intermittent or corrupt, it will cut it off completely and stick with the backup data line.

Offline pixelpuppy

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Re: WS2813 or WS2818 pixels?
« Reply #12 on: December 31, 2018, 08:33:45 AM »
How does one chip klnow that the preceding one is dead? 
when it stops receiving a signal on the Data Input but is still getting a good signal on the Backup Input 
Quote
What happens if two chips in a row are dead?
This backup method can handle multiple pixel failures in the same string, but not when the two bad ones are immediately sequential to each other (one bad pixel followed immediately by another bad pixel).  However, that is a much more rare occurrence.
If I remember, if data is used off the back-up line, then it knows to remove one pixel (thus keeping everything in sync).
That's correct.  This way, the sequencing does not change or shift.
Quote
To me, it seemed like an upgrade that may solve some (but not all) of the potential scenarios when a pixel goes bad.
Also correct.  Its good for those failures where a bad pixel stops everything after it from working.  It does not handle the case where a pixel gets stuck on one color or is missing a color, but still passes data (I've had a bunch of those this year  :-\  ).  With that said, the former is the type of problem that makes you want to go out at night and fix (splice) the bad pixel right away but the latter is the type of problem that can usually wait until its more convenient to fix.  So this solution helps reduce the need or desire to do those late night field repairs  ;D
All the chip does is look at the two inputs and if it sees an input on the backup and not on the normal input, it shuts down the normal input and pulls data from the backup input and knows to strip off the first 24 bits of data before processing and reshaping the data stream so the proper channel number is maintained.  The protection only goes for a one node in a row failure but most of the time, that's exactly what happens.
Exactly.

Offline jnealand

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Re: WS2813 or WS2818 pixels?
« Reply #13 on: December 31, 2018, 08:51:35 AM »
Thanks for the education guys.  Sounds very interesting.  Must say that over my 6 years using pixels I have not had many failures that this would fix so if the price is higher I would probably not opt for these.  That being said, I think (hope) I never have to buy pixels again in my lifetime (I'm 76) as I bought a ton this year and upgraded most of my older pixels.  Now I have a lot (several hundred) of "older" pixels I can play with as well as several hundred brand new ones that did not make it into a prop for this years show.  I love to see all this new stuff.  Things are quite different from when I first got into animation 12 yrs ago.  This year was my best show ever and I am running out of ideas to up my game.  LOL

Offline algerdes

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Re: WS2813 or WS2818 pixels?
« Reply #14 on: December 31, 2018, 09:08:56 AM »
Up to this year I would agree with Jim.  Unfortunately we have had failure after failure with square nodes this year.  Perhaps age, perhaps weather related, but still an awful lot.  This type of function might have allowed me not to be in the field so much - repairing pixels because of whole strings being out.


I can see this being very handy for someone who has pushed the limits of the controller and connected huge numbers of pixels to the same output.

 

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