K8-B

What is it?

The K8-B is a cape for the BeagleBone Black designed to drive ws2811 LED pixels. It has 8 local ports (fused with LED indicators) that can each drive 800 pixels (with power injection) at 40FPS. It also has 3 RJ45 differential ports that can output an additional 12 strings using differential receivers. Finally, there is an expansion header which can drive an additional 16 strings. The 800 pixels per string is the same for all strings. There are also two UARTs exposed via header pins which can drive DMX universes or Renard or LOR.

It also provides a Real Time Clock, temperature sensors, a header for an OLED display, and four push buttons for navigating menus on the display.

Why did you make it?

Animated Christmas Light displays typically use ws2811 Pixels for things like house outlines, candy canes, tree’s, etc… The K8-B was designed to drive a large number of pixels, yet remain relatively small so it can be easily hidden or mounted onto the prop.

What makes it special?

The 8 local ports provides enough outputs to handle most situations where a small controller is desirable. It’s significantly more than the 2 ports of the various Raspberry Pi controllers, but not as large as the standard 16 port controllers that are typically used for pixel dense locations.

However, the 3 RJ45 ports provide additional output capabilities to allow for future expansions. All 3 of the ports can be configured to drive a ws2811 pixel differential receiver board (available from pixelcontroller.com ). Both “Falcon Smart Receivers” and standard differential receivers are supported.

The 40pin expansion header also can drive additional pixels. There are 16 strings that are pulled out on the expansion header. This is compatible with the F16v3 expansion boards.

The BeagleBone can be powered by the same power supply powering the pixels. It can be powered from the cape using power between 5V and 18V. Alternatively, the BeagleBone can be powered by its own barrel connector if an on-board jumper is removed, however this is discouraged.

Technical details: The ws2811 protocol is extremely timing dependent and are generally not drivable via a general purpose Linux CPU. The FPP software uses the two semi real-time PRU’s available on the Beagle to handle the protocol specific timings. Using the PRU’s also allows the main CPU to be free for other things such as network IO.

You WILL need:

• ws2811 pixels
• A good quality SD card with the latest FPP image installed on it. The latest FPP image can always be found at https://github.com/FalconChristmas/fpp/releases
• A BeagleBone Black, BeagleBone Black Wireless, BeagleBone Green, or SanCloud BeagleBone enhanced.
  Note: a BeagleBone Green Wireless will NOT work.