added README

README.md

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+![Nicht verbrennen!](/images/fackel.jpg)
+# flame.ino
+
+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.
+
+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