Interfacing Adafruit’s Digital Addressable RGB LED strip (aka “LPD8806 strip”) to the Raspberry Pi is super simple, requiring just a few connections between the board, strip and a DC power jack.
The board’s MOSI pin connects to the DI pin on the LED strip, and SCLK connects to the CI pin.
Instead of supplying power to the Raspberry Pi’s Micro USB connector, a 5 Volt DC power supply is required because the LED strip draws significantly more current than the USB input can provide. A 2 Amp power supply is sufficient for a 1 meter LED strip, while our larger 10 Amp supply can power up to 5 meters of LED strip (plus the Raspberry Pi board, in both situations).
+5V and ground from the power supply connect to the 5V and GND pins on both the LED strip and the Raspberry Pi GPIO header.
In the above diagram, we’re directly connecting 3.3V logic output from the Raspberry Pi to the 5V logic input of the addressable LED strip. Strictly speaking, this is not Good and Proper. Wildcards like actual power supply voltage (they’re never precisely 5.0000V) or even temperature may contribute to whether this functions reliably. It did very well here, but your mileage may vary. If your LEDs almost work but are glitchy, it’s time for a logic level shifter, explained in this guide (which is about NeoPixels, but the principle is the same — just that we’ve got two wires to level-shift here, rather than NeoPixels’ one).