Capture-Read-Receive-Analyze a WS2811/12 pixel signal

[DrWizard]

Can anyone point me to a sketch or library which will read-capture and analyze a datastream in WS2811 or 2812 format?  Basically the opposite of FastLED or AdaFruit NeoPixel libraries?  I've been Googling and searching forums for an hour now and can only find stuff about outputting the signal.

[Grumpy_Mike]

We had a thread in here about a month or two ago that was basically asking the same thing. The consensus was you could not do it with a Uno you needed a faster Arduino and no one had done it yet.

Why do you want to do it?

[DrWizard]

It doesn't necessarily have to be Arduino.  I have ESP8266's, ESP32's, STM32's TM4C1294's, and RTL8710's in my collection.

I am trying to troubleshoot the pixel-installation-from-hell and trying to build a portable tester-analyzer for locations I can't easily bring the laptop (ie: steep roof).  My logic analyzer captures the signal, but won't decode it, I have to do that 'by hand' which is a pain, and again, I can't easily carry the laptop to the problem.

I don't have time to write something from scratch, and not sure my coding skills are quite to that level anyway.  I need to resolve this pixel problem ASAP.

[Grumpy_Mike]

I don't have time to write something from scratch, and not sure my coding skills are quite to that level anyway.  I need to resolve this pixel problem ASAP.

Sorry I think you are on your own on this one.

[mcnobby]

You could probably do this with a Nano/Uno, but it would all need to be written in assembler and totally block any other functions at the time of reading.

As for analysing the data at the same time, I dont think there would be enough time to do anything like that as we are talking 1250ns per bit (at 800KHz), which is only 20 clock cycles (at 16MHz)

But you could probably output the byte received from the UART at 1MBPS) which would take no processor overhead apart from loading the byte into the register) what you do with it then will be up to you

I have written many versions of WS2812/SK6812 bitbashers for ATTiny, ATMega etc and a Scope (with storage) is an absolute minimum requirement for getting it right !
 
Bob

[maeterlinck]

Hi all,
I know this is a oldish thread, but I was wondering if anyone had had any further luck on this?
We're looking at a similar project and wanting to achieve such a device in lightweight hardware.
Thanks,

[PaulRB]

No, I have not heard that anyone has done this yet. It is a difficult thing, and only a few people need to do it. Most libraries are provided for free in order to sell something, like an RGB led strip or a temperature sensor or an LCD display. But a library to do what you asked could not be used to sell anything to a mass market, I suspect. So you need to find an expert or a group of experts who are willing to do it for free or for payment. How much is such a library worth to you? You could post in the "gigs and collaborations" section. Others who would also benefit might reply and add more cash to the offer, until someone decides it is enough for them to try and claim the prize.

[mcnobby]

I have done it with an ATTiny13A to drive servos and steppers, but unfortunately it in AVR assembler and currently in a non-disclosure situation, it can also be done on a UNO/Nano, but not in library form as the timing is very very crucial

[stewey]

I have done it with an ATTiny13A to drive servos and steppers, but unfortunately it in AVR assembler and currently in a non-disclosure situation, it can also be done on a UNO/Nano, but not in library form as the timing is very very crucial

Hi, I'm essentially looking to do the same thing, controlling something else within an WS81X run. Really happy to see you have proved concept with an ATtiny. Are you still in a non-disclosure situation? Are you perhaps up for giving any tips in the right direction, words of warning?

[Smajdalf]

I think it is not so difficult. If I had to do something like that I would try to make a WS2811 - SPI bridge from  ATTiny13A (or ATTiny10). The program probably needs to be written in assembly but should be short and simple.
More tricky option is to delay the signal for 1us or so. Than it should be possible to read it as SPI (delayed signal used as clock and the original one as data).

[stewey]

Thanks, that's given me another avenue for experimentation