Add second example for regular NeoPixel strip (not CPX built-in pixels)

Author: PaintYourDragon

examples/neopixel_rotate.py

@@ -0,0 +1,72 @@
+""" Simple FancyLED example for NeoPixel strip
+"""
+
+import board
+import neopixel
+import adafruit_fancyled as fancy
+
+# Function names are kept the same as FastLED examples, which normally
+# upsets pylint.  Disable name-checking so this passes muster.
+# pylint: disable=invalid-name
+
+NUM_LEDS = 23
+
+# A dynamic gradient palette is a compact representation of a color palette
+# that lists only the key points (specific positions and colors), which are
+# later interpolated to produce a full 'normal' color palette.
+# This one is an RGB spectrum -- red to yellow, green, blue, ... back to red.
+RAINBOW = bytes([
+    0, 255, 0, 0,
+    32, 171, 85, 0,
+    64, 171, 171, 0,
+    96, 0, 255, 0,
+    128, 0, 171, 85,
+    160, 0, 0, 255,
+    192, 85, 0, 171,
+    224, 171, 0, 85,
+    255, 255, 0, 0])
+
+# Here the gradient palette is converted to a full normal palette.
+# First we need a list to hold the resulting palette...it can be
+# filled with nonsense but the list length needs to match the desired
+# palette length (in FastLED, after which FancyLED is modeled, color
+# palettes always have 16, 32 or 256 entries...we can actually use whatever
+# length we want in CircuitPython, but for the sake of consistency, let's
+# make it a 256-element palette...
+PALETTE = [0] * 256
+fancy.loadDynamicGradientPalette(RAINBOW, PALETTE)
+
+# The dynamic gradient step is optional...some projects will just specify
+# a whole color palette directly on their own, not expand it from bytes.
+
+# Declare a NeoPixel object on pin D6 with NUM_LEDS pixels, no auto-write
+PIXELS = neopixel.NeoPixel(board.D6, NUM_LEDS, brightness=1.0,
+                           auto_write=False)
+
+def FillLEDsFromPaletteColors(palette, offset):
+    """ This function fills the global PIXELS NeoPixel strip from a color
+    palette plus an offset to allow us to 'spin' the colors.  In FancyLED
+    (a la FastLED), palette indices are multiples of 16 (e.g. first palette
+    entry is index 0, second is index 16, third is 32, etc) and indices
+    between these values will interpolate color between the two nearest
+    palette entries.
+    """
+
+    for i in range(NUM_LEDS):
+        # This looks up the color in the palette, scaling from
+        # 'palette space' to 'pixel space':
+        color = fancy.ColorFromPalette(
+            palette, int(i * len(palette) * 16 / NUM_LEDS + offset),
+            255, True)
+        # Gamma correction gives more sensible-looking colors
+        PIXELS[i] = fancy.applyGamma_video(color)
+
+# This is an offset (0-4095) into the color palette to get it to 'spin'
+ADJUST = 0
+
+while True:
+    FillLEDsFromPaletteColors(PALETTE, ADJUST)
+    PIXELS.show()
+    ADJUST += 50  # Bigger number = faster spin
+    if ADJUST >= 4096:
+        ADJUST -= 4096