add pulse example

micropython/examples/plasma_stick/pulse.py

@@ -0,0 +1,42 @@
+import time
+import plasma
+from plasma import plasma_stick
+from math import sin
+
+"""
+Simple pulsing effect generated using a sine wave.
+"""
+
+# Set how many LEDs you have
+NUM_LEDS = 50
+
+# we're using HSV colours in this example - find more at https://colorpicker.me/
+# to convert a hue that's in degrees, divide it by 360
+COLOUR = 0.5
+
+# set up the WS2812 / NeoPixel™ LEDs
+led_strip = plasma.WS2812(NUM_LEDS, 0, 0, plasma_stick.DAT, color_order=plasma.COLOR_ORDER_RGB)
+
+# start updating the LED strip
+led_strip.start()
+
+offset = 0
+
+while True:
+    # use a sine wave to set the brightness
+    for i in range(NUM_LEDS):
+        led_strip.set_hsv(i, COLOUR, 1.0, sin(offset))
+    offset += 0.002
+    
+#     # our sine wave goes between -1.0 and 1.0 - this means the LEDs will be off half the time
+#     # this formula forces the brightness to be between 0.0 and 1.0
+#     for i in range(NUM_LEDS):
+#         led_strip.set_hsv(i, COLOUR, 1.0, (1 + sin(offset)) / 2)
+#     offset += 0.002
+    
+#     # adjust the saturation instead of the brightness/value
+#     for i in range(NUM_LEDS):
+#         led_strip.set_hsv(i, COLOUR, (1 + sin(offset)) / 2, 0.8)
+#     offset += 0.002
+
+