Hexascroller has been a central fixture at NYCR for the past few years, with a few ups and downs. It’s replacement, Octoscroller, improves on our classic message alert polygon by having two more sides and two more colors of LEDs.
The brains are a BeagleBone Black running the LEDscape custom PRU firmware. The AM355 CPU in the BBB has two separate realtime microcontrollers built into its die, both with full access to the GPIO lines and cache coherent access to main memory. This bit of hardware/software allows the user application to simply render into a frame buffer, which is then driven to the panels by the PRU.
The key component of Octoscroller are these 16×32 RGB panels from Adafruit. Unlike the popular WS281x LED strips that have their own PWM hardware builtin to each pixel, these panels are very inexpensive since they require continuous refresh by an external driver. The Arduino firmware can only drive a single panel and consumes a significant amount of CPU interrupt time to maintain the image. With LEDscape, the BBB can drive up to four chains of four panels each at 0% CPU load. Powering the panels and the BeagleBone is a 5V 10A DC supply
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