The simple answer is the integrated FPGA, and RS-422 drivers, for a more in-depth answer, read on...
Obviously there are a number of differences between the BeagleBoard Black and Khon from a hardware standpoint. But when it comes to controlling LEDs, the main difference is the on-board dedicated FPGA ---
Khon's Xilinx Spartan6 FPGA is used to generate the 16 simultaneous LED channel outputs, there is enough logic gates and memory in the FPGA to double this to 32 channels, but we decided to use the additional logic and 16 I/O signals for the SDRAM interface. (This could be changed in the future)
The Beaglebone Black could probably use its integrated PRU controllers to generate the LED data stream with very little CPU intervention, otherwise the CPU would be tied-up in dedicated tight-timing loops (I/O bit-banging) or possibly use timer resourced interrupts to generate the LED data stream.
Either way, there is really no comparison between a PRU (or CPU I/O bit-banging) and a dedicated FPGA for LED control, especially when it comes to added features like real-time support for synchronizing special effects, adding an alpha channel, or masking pixel data to an external event. From a hardware point of view, the FPGA is simply a better solution with parallel processing capability and programmable dedicated logic, it ends up being a very powerful simple to use LED controller.
With integrated FPGA hardware, the real advantage is when it comes to high-level programming, Khon's FPGA is a 24-bit RGB LED pixel controller with a very powerful user programmable interface. Also the full LED pixel framebuffer is located in the FPGA's dual-ported block RAM, giving simultaneous access to Khon's ARM CPU DMA engine for writing data and read access to the 16 parallel output controllers that generate the LED data streams.
Our FPGA pixel controller includes registers for the pixel output start address and pixel count, also the DMA pixel write address is programmable so any portion of the LED pixel framebuffer can be written quickly to generate very fast frame update rates.
The FPGA and CPU have direct access to the microSD card, giving all kinds of possibilities, including extremely long animations/messages or a host of special effects.
Our FPGA Framebuffer ICD document will be published shortly on the KromaLights website, also our open source application SDK will be on GitHUB soon. We have example programs written in Java and VB.net showing how easy it is to use Khon to program LED panels or light sticks with advanced features, including full color animations, scrolling rainbow marquee text banners, LEDs synchronized to sound sources, and the list goes on and on... your imagination is the limit.
In the end, would you rather spend your time concentrating on your feature rich LED lighting application using Khon's FPGA based RGB LED controller or programming the Beaglebone PRU's in assembly language, which in itself can be hard to document and maintain?
Khon-Plus also includes an on-board Bluetooth 4.0 module for smart phone based remote control applications and hardware audio support for synchronizing music or other sound sources.
Our breakout board includes RS-422 drivers, with RJ11 connectors, this simplifies and provides a more robust connection to the LED panels. Khon will also drive other vendor panels that support the Worldsemi WS2812B RGB LED, you would then connect the control lines directly to Khon's buffered I/O LED connector.