I have a row of WS2812B on my PCB. I have 3 identical PCBs, and on 1 board the WS2812Bs are "twitching". They are showing colors just fine, but RGBs are flickering / twitching repeatedly. It happens very quickly but nonetheless very visible. Has anyone seen this issue in the past?

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    \$\begingroup\$ Did you decouple them properly? \$\endgroup\$ – Ignacio Vazquez-Abrams Nov 21 '17 at 23:54
  • \$\begingroup\$ @IgnacioVazquez-Abrams yes there is 0.1uF on every VCC. \$\endgroup\$ – Adam Lee Nov 22 '17 at 0:09
  • \$\begingroup\$ I have not seen that before, and this is only a wild guess: maybe something is happening on the data line. If you have access to an oscilloscope it is easy enough to check. \$\endgroup\$ – MAB Nov 22 '17 at 1:30

I figured out the solution. It has nothing to do with electrically. My contract manufacturer flashed the MCU via ISP and in the process they changed the fuse bits. I have since reset the fuse bits to the default and it no longer exhibits this issue.

Default fuse bits:
L 0x5E
H 0x99
E 0xF3
LB 0x2C

This is quite puzzling nonetheless. I will update once I figure out the exact fuse bit that resulted in the random flicker.

  • \$\begingroup\$ What were the fuse bits set to? \$\endgroup\$ – Ignacio Vazquez-Abrams Nov 23 '17 at 19:42
  • \$\begingroup\$ @IgnacioVazquez-Abrams Sorry I am curious myself as well. I didn't get to save it. \$\endgroup\$ – Adam Lee Nov 24 '17 at 4:28

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