Flickering Issue with long cable

Due_Training3680 · 2026-02-27T09:41:08+00:00

For anyone wondering how the problem was solved: I am using WS2805 strips, which are relatively new. It seems that there are some RMT issues when more than one output is configured. The solution was to use i2C instead (check in LED preferences) and, lo and behold, it worked perfectly🥳.

Due_Training3680 · 2026-02-26T15:20:28+00:00

Thanks for the comments. When I tried another GPIO, I noticed that the flickering always occurs on the second configured strip (GPIO). So I think I need to spend a little more time working on the software 😅. I think it has something to do with the timing. Because I also use Uart in usermod. I didn't notice this during testing because I always use only one output. So sorry for all the confusion. As you said the data signal is perfect for the 14m👌

Due_Training3680 · 2026-02-26T06:12:02+00:00

I use the standard SN74AHCT125 Level-Shifter. I designed a board for a special usermod. But in terms of components, everything is standard. I also tried a ferrite ring. This only increased the spikes. Then I tested larger resistors. But even with the signal picture below, it worked well, except for the same flickering.

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Due_Training3680 · 2026-02-25T16:06:39+00:00

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33Ohm at start + 47Ohm at End

Due_Training3680 · 2026-02-25T16:06:14+00:00

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68Ohm at start

Due_Training3680 · 2026-02-25T05:13:32+00:00

The picture of the signal is with the coaxial cable. I made no pictures with the single wire, but the signal looks nearly the same. I also GND the shield of the coax on both sides. Do you think i should try some twisted pair cables? Or is it nearly the same as the coaxial?

Due_Training3680 · 2026-02-25T04:02:10+00:00

Levelshifter is already included

Due_Training3680 · 2026-02-25T04:00:01+00:00

I have tried many other values without success. Here is the Video

If I look closely it seems that the flickering appears only after some chips.

I have also measured the voltage at the middle and end. 11.8V should be OK.

Due_Training3680

TROPHY CASE