Level Shifter to run 5V NeoPixels (WS1812B) LEDs via a 3.3V SPI bus (e.g. Raspberry Pi).
The P-SPI header was designed in such a way, that the PCB can be plugged on top of the Raspberry without further cabeling. The P-LED-DRIVE outputs the signal to the LEDs, while P-LED-SENSE optionally connects to the output of the last LED in the chain. Connecting P-LED-SENSE allows a software running on the Raspberry Pi to detect the number of LEDs in the strip.
In order to drive the WS1812B LEDs you need to generate a specific bit pattern on the SPI bus on a specific clock speed. Have a look here for a library which can do this: https://github.com/SIGSEGV111/ws281x-spi-driver
There are three ways to power this board:
you connect P-POWIN to an external power supply and leave P-GPPOW disconnected This will run the LEDs from the external supply, the Raspberry (or whatever drives P-SPI) will run from its own power supply (e.g. USB). In this configuration you have two power supplies, one for the Raspberry and one for the LEDs.
you connect P-GPPOW to the Raspberry to draw power from it and leave P-POWIN disconnected This will draw power from the Raspberry Pi to power the LEDs. Keep in mind that this will only suffice to power about 10 LEDs. More might damage the Raspberry Pi, or overload the USB power supply. The advantage here is that you do not need another power supply.
you connect P-POWIN to an external power supply and P-GPPOW to the Raspberry YOU MUST NOT CONNECT A USB POWER SUPPLY in this configuration The Raspberry Pi will be powered from the external power supply aswell. This eliminates the need for an additional USB power supply and still can drive more LEDs.