Answered Misbehaving SK6812 pixels

[Kingfisher]

Hi,
I'm having a bit of trouble with some SK6812 pixels. These are the ones I brought - https://a.aliexpress.com/_mMT7GM2

I have cut these strings into smaller strings to make props with, mainly wrapping them around some shapes.

My problem is that the pixels seem to be remembering there previous addresses from before I cut the strings.
I have cut these for other uses in the past and they have worked. So I am confused with why they won't work.

I am using the original controller to test them as I build.

Any help with this will be appreciated. Ask me any questions and I'll try my best to answer them.

Thanks.

P.S. I have contacted the seller to confirm the actual IC that is used, and have not yet heard back from them.

 

[Mark_M]

Just curious;
For a complete string of these lights is there a noticeable 'repeat' every 'x' nodes? Say every 30 nodes the pattern is the exact same.

Might be worth trying with a controller you can set a pattern through xlights with.

 

[Notenoughlights]

When you say remembering their previous addresses, what do you mean by this? Have you addressed each pixel like you would do with a DMX light fixture?

 

[AussiePhil]

seems weird as the SK6812 seems to be just another 2811 variant https://cdn-shop.adafruit.com/product-files/1138/SK6812+LED+datasheet+.pdf

 

[Kingfisher]

Just curious;
For a complete string of these lights is there a noticeable 'repeat' every 'x' nodes? Say every 30 nodes the pattern is the exact same.

Might be worth trying with a controller you can set a pattern through xlights with.

It's not a repeating pattern every X nodes.
Its more like this,
Node 1-30 are working correctly and displaying as expected
Node 31-60 are working correctly and displaying as expected
Node 61-90 are doing the same thing as nodes 31-60.
I don't have any more than 60 nodes set as I hit this issue and tried to troubleshoot, with no luck currently.

I have not yet connected it to a controller and up to QLC+ (the software I'm using to control them all), however I suspect that it won't change much.

When you say remembering their previous addresses, what do you mean by this? Have you addressed each pixel like you would do with a DMX light fixture?

It's a bit difficult to explain what I mean. It's like the nodes are well just that, acting as if they are still in the order that I got them when I brought them.
I definitely did not address them similar to standard DMX fixtures, and as far as I know there is no way to do this with sk6812 nodes.
As @AussiePhil said, these nodes act just like ws2812 nodes, and it is kinda weird that they are acting this way.


There are a few things I'm gonna try;
1) an Arduino nano based E1.31 controller
2) an Artnet controller
3) adding a standard ws2812 node at the start of the chain

I've just managed to upload a short video of my issue. It is only 90 nodes and it's not the best video, but hopefully it will be able to make it easier to understand the issue.
They are in order in the chain, the bottom one is first going up.

View: https://drive.google.com/file/d/1YjFPQTgNAELR-S8-raPb10JSBMqAcr/view?usp=drivesdk

 

[AAH]

These look like they could well be the exact same thing as in https://auschristmaslighting.com/threads/pixels-in-parallel-yet-still-addressable.13976/

 

[Kingfisher]

These look like they could well be the exact same thing as in https://auschristmaslighting.com/threads/pixels-in-parallel-yet-still-addressable.13976/

Yeah I suspect that the data line is in parallel. But I haven't checked, I'll do that when I have the chance. I don't think it's exactly the same but I could be wrong.
However somehow these have worked as if they are just standard nodes in the past with other builds. It's kind of odd.

Edit: actually I think that they may be more like those than I suspect, I'll do some more investigations on this.

 

[Kingfisher]

Ok, so I think I have figured it out. Thanks to everyone one who helped especially @AAH who linked me to the other post, that really did help.

So these pixels appear to be pre-addressed and while that's not a massive problem for me and my application, because I didn't know this when I was cutting the strings up, i ended up mixing everything up, leading to this problem.

My fix to this is to use 3 new strings and rewrap the shapes while also soldering them together, thus ensuring that This issue doesn't appear again.
I also have to now double check my other prop that I made that used the same leds, to see if there is an issue there or not, and possibly have to rebuild those.
I know that this is a bit of a waste but I am not prepared to sort out where in the string each node belongs and deal with that mess.

I don't think that people have figured out a way to re - address these, if anyone knows please do let me know.

Thanks again to everyone who helped.