Driver for WS2812 RGB LEDs (NeoPixels, ...)

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torwag
Posts: 197
Joined: Fri Dec 13, 2013 9:25 am

Re: Driver for WS2812 RGB LEDs (NeoPixels, ...)

Post by torwag » Tue Feb 07, 2017 8:09 am

Beside of deshipus comment,
many sources on the net state that you should use some resistors and blocking capacitors in front of the first LED since they tend to be quite easily harmed by voltage spikes. Honestly, speaking I never did this and did not kill a single LED yet. Just wanted to mention.
Also take into account that the 3.3 V logic level might seems to be sufficient on the test-bench but the 3 m wire from the controller to the LED-stripe in the final application might create a lot of head-scratching ;)

Hmmm. thinking more about it, I wonder if the logic-level theory fits... since, if the first LED only receives rubbish digital values, it just forwards digital rubbish at now 5V to the other LEDs. However, I remember to read that the level shifters in the LED are more forgiving then other parts of the LED circuitry. Ultimately, I guess deshipu is right to say it would be much better to adapt the logic level.

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deshipu
Posts: 1251
Joined: Thu May 28, 2015 5:54 pm

Re: Driver for WS2812 RGB LEDs (NeoPixels, ...)

Post by deshipu » Tue Feb 07, 2017 11:38 am

My sources:

https://hackaday.com/2017/01/25/ws2812b ... originals/
http://hackaday.com/2017/01/20/cheating ... data-line/

Re-reading this again, I agree that it doesn't quite add up in my theory -- it's probably some kind of a timing problem.

calyerm
Posts: 1
Joined: Mon Nov 20, 2017 4:20 pm

Re: Driver for WS2812 RGB LEDs (NeoPixels, ...)

Post by calyerm » Mon Nov 20, 2017 4:28 pm

After looking with logic analyzer on data line , the timing does not appear to be correct. The baudrate clock is good but the
neopixel bit low and high pulse widths are not right. For this clock (baudrate is actually 262500) Need 1/4 ratio for neopixel bit low and 2/2 ratio for neopixel bit high. Correction: Thats 2/4 ration for high.

cefn
Posts: 78
Joined: Tue Aug 09, 2016 10:58 am

Re: Driver for WS2812 RGB LEDs (NeoPixels, ...)

Post by cefn » Sat Nov 25, 2017 12:58 pm

@calyerm what was your configuration (software/hardware) when you ran the logic analyser?

Were you using https://github.com/JanBednarik/micropython-ws2812 as per the original post viewtopic.php?f=5&t=394#p2199

cefn
Posts: 78
Joined: Tue Aug 09, 2016 10:58 am

Re: Driver for WS2812 RGB LEDs (NeoPixels, ...)

Post by cefn » Sat Nov 25, 2017 1:01 pm


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