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For my project I have bought two simple boards with RGB LED's on them (WS2812 based, product description). I already had similar one with single LED that I connected with four wires: Red channel, Blue channel, Green channel and GND. It worked well with simple GPIO.output commands.

enter image description here

This one however has quite strange connections (check the photo. I soldered wires to all available contacts and connected it to Pi. VCC as power to 3,3V, GND as GND and DIN/DOUT to two GPIO pins I tried to set output to. But whatever I do, the LED's won't light up.

EDIT: Just a quick progress update. I tried various stuff to light the LEDs, even using Neopyxel library but so far no luck. I guess this is out of my "knowledge-zone" :-) For now.

  • It looks like a WS2801 or similar. They need a continuous digital stream of commands. Search for WS2801. – joan Nov 1 '16 at 18:49
  • @joan it seems to be more of an WS2812 or similar. WS2801 should have an additional clock input. – Ghanima Nov 1 '16 at 19:02
  • Filip, it is always helpful to provide a link to the datasheet of the item in question, although one might guess that CJMCV-3 will be a useful hint to its identity. – Ghanima Nov 1 '16 at 19:04
  • @Ghanima bought it here: gearbest.com/lcd-led-display-module/pp_346864.html I did not realize that in the title could be useful info. However the datasheet I found (cdn-shop.adafruit.com/datasheets/WS2812.pdf) does not match – Filip Nov 1 '16 at 19:39
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    Note that each of these LEDs actually has a built-in IC to process the data and convert it into the red/green/blue outputs for you. WS2812-style LEDs are difficult to control with the Raspberry Pi because of the precise timing you need for the data signal. If you can get a similar module with APA102-style LEDs, that will work the same way but will be much easier to control reliably. (Or you could find one with three normal LEDs and use 9 GPIOs to control the red/green/blue pins of each one) – immibis Nov 1 '16 at 22:04
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As Joan mentioned in the comments its probably PIN's that expects data.

  • DIN - Data in
  • DOUT- well that may be a PIN that sends DataOUT

If it were a simple RGB LED you would have PIN's for R,G,B and GND.

While executing a query on an index engine I came to find the PCB uses WS2812 - You can click on the link to see the specifications of the LED thingy.

Reading that tells you have to send PWN signals to the device and what the Data OUT pin is for. Essentially this PCB is used to create larger arrays of chained LED's - Imagine outdoor signage or even massive TV's used at sport grounds or similar.

enter image description here

And you could probably build this usefull LED curtain using these modules.

enter image description here

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    I think you'll need more than two for that :p – Jaromanda X Nov 2 '16 at 4:02
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DIN/DOUT to two GPIO pins I tried to set output to

Note that DIN is a control data signal input (input at the LED) and DOUT is a control data signal output (output at the LED). The DOUT of one module is typically used to chain to the next LED module. Do not connect DOUT to a GPIO pin of the Pi that is set to output.

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