Basic demo of WS28xx (800 MHz) communication protocol using the Atmel XMega USART in master SPI mode. Also uses DMA to automatically transfer the data to the USART.

The XMega is running at 32 MHz, and the USART is running at 3.2 MHz. This means that a single bit has a width of (1 / 3.2 MHz) = 0.312 microseconds. Based on the timing diagram a single pulse will work for both the T0H pulse and the T1L pulse. Three bits equal 0.9375 microseconds, which satisfies the timing for the T0L and T1H pulse widths. So, a single bit for the WS28xx is created using 4 bits on the USART.

By default, the SPI defaults to a high logic level when high. The WS28xx needs to be logic level low at idle. To fix this, we just invert the output of the data pin and invert the logic levels going into the USART.

This has been tested using an XMega32a4u and a single Adafruit NeoPixel Clear 5mm Through-Hole LED.

Unless otherwise noted, all files are covered by the Blue Oak 1.0.0 license as described in the LICENSE.md file.