The CJMCU 8*8 LED board is a grid of 64 W2812 (addressable) LEDs. The board is configured as if it was one long LED strand (just a single DIN, 5v and GND). For some flipping hair pulling reason, my code works fine on 2812 LED strands, but I get nothing on the board. Just random flickering when I jostle the 5V wire. Any ideas? Am I completely missing something here? Pretty sure the board is fine, just can't seem to take any input...

(Here's a link to the board: http://www.aliexpress.com/store/product/CJMCU-64Bit-WS2812-5050-RGB-LED-Development-Board-Built-in-RGB-Driver-White-SKU-11481/933826_32249197598.html)


3 Answers 3


I just received 2 of these from 2 different suppliers on EBAY. None work using the pins called [GND +5V DIN]. As it turns out the DIN is actually NOT DIN. The other connector area [GND +5V DOUT] is the DIN. Ugh!

These boards are marked CJMCU-8*8 on the back side and on the front they say "WS2812B-64 RGB LEDS". Which is another issue. They are using the 6 pin WS2812, not the 4 pin WS2812B.

So if this is what your board looks like then perhaps try the pin marked DOUT for your DIN. Or try to psych out the traces to make sure first.

  • Had the same issue, turned out that DOUT swapped with DIN. Thanks for a hint.
    – dawidku
    Jan 15, 2017 at 21:42
  • Thanks for the awesome tip about DOUT. I hooked up that one instead and now the matrix works fine. Geez.
    – VicLovin
    Feb 13, 2017 at 3:39

Unbelievably, as I've just discovered, this has been a known issue with these boards for at least a year and a half, yet they are still shipping them. The silk screening process of labeling the board is the problem. Just poor quality control. The front (LED) side of these low quality CMJCU-8*8 boards are incorrectly marked "SM2812B RGB LEDS". (The actual LEDs are 6 pin SM2812's, not 4 pin SM2812B's), but the real problem is with the back side of the board. The manufacturer printed the boards upside down, so that the input and output labels are reversed (DIN is really DOUT and vise versa).

I just purchased one of these defectively printed boards on line and received it a few days ago. Took me awhile to figure out why I couldn't get it to work, but I finally did. When hooked up backwards, the CMJCU-8*8 will do nothing at all (no LEDs will come on), because of the built in reverse polarity protection, but if you run your thumb hard (it's just +5V) over the other pins (the ones that include the erroneously marked DOUT) while the board is powered up, one or more of the SM2812 LEDs will magically come on. This is because your thumb makes an intermittent connection between the real DIN and the +5v rail, providing a forward bias to a few random LEDs. Once lit, these LED's will actually stay on until you cut power to the board, so if you keep ding it, you can get quite a few of the SM2812s to come on.

CMJCU-64 Printing Error

  • My CMJCU-8*8 board is labelled correctly, so try they DIN pin first. Mar 16, 2018 at 9:49
  • Hi, I wouldn't have any of the leds come on if this were still the case with my board, right ? I can only get the first two rows (or columns) to light up. They're not lighting up in a way that I would expect if the rest of the LEDS was broken (random colors, random brightnesses, no apparent logic) Oct 12, 2019 at 21:38
  • I just tried it, only one LED will come on, bright blue, somewhere on the third row... Oct 12, 2019 at 21:52

Literally spent hours painstakingly chasing same problem. Complained bitterly to supplier that board refused to respond or operate when received. They responded by trying to tell me I had no clue about how to connect, but eventually agreed to send replacement after I proved had connected correctly, while waiting for replacement came across this post, went and found original board and reconnected, 5V to DIN side, and DIN to DOUT (Instant operation) because the reverse polarity protection does not prevent being energized this way. if supplier comes good, will have another board to compensate my trouble.

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