This is a small arduino sketch to drive a string of WS2812 LEDs wound around a tube, to simulate a flaming torch.
I have carried around the torch on various events and it has proven quite popular and served as inspiration for other similiar builds, see for example the work of Lukas, who expanded on the idea and added message scrolling: https://github.com/plan44/messagetorch
This code is built for 5m LED strip with 64 led/m. The circumference of the tube is about 17-20 cm, so that after 12 leds one winding is complete.
This is an arduino sketch, however, there are two small issues with this:
It needs a patched Adafruit-Neopixel library, where I extended the constructor with a pointer to pre-allocated memory. That way I get some control on where in the memory the framebuffer is residing.
Also, the memory in the arduino leonardo for 320 LEDs is tight. It tends to interfere with the bootloader activation since the "Catarina" Bootloader relies on some values in very specific memory locations to decide if it starts the main application or not. This value sometimes gets clobbered by the flame rendering code, in extreme cases it might be necessary to reflash your leonardo via ISP.
I tried to keep the code clean and have the most important values as defines, so that it can be adjusted to different led layouts.
Have fun! Simon