gistfile1.py

import time, os

try:
    import RPi.GPIO as GPIO
except ImportError:
    GPIO = None


class Color(object):
    def __init__(self, r, g, b):
        self.r = r
        self.g = g
        self.b = b

    def as_int(self):
        return ((self.r & 0xFF) << 16) | ((self.g & 0xFF) << 8) | (self.b & 0xFF)


class Lights(object):

    def __init__(self, pixel_count, mode="hardware"):
        self.pixels = [Color(0 ,0 ,0)] * pixel_count
        self.mode = mode

        if not GPIO:
            print "Cannot render hardware, no GPIO module, rendering screen"
            self.mode = "screen"

    def set(self, offset, color):
        self.pixels[offset] = color

    def render(self):
        if self.mode == "hardware":
            spidev = file("/dev/spidev0.0", "w")
            for i in range(len(self.pixels)):
                spidev.write(chr((self.pixels[i].as_int() >> 16) & 0xFF))
                spidev.write(chr((self.pixels[i].as_int() >> 8) & 0xFF))
                spidev.write(chr(self.pixels[i].as_int() & 0xFF))
            spidev.close()
            time.sleep(0.002)
        else:
            line = ""
            for i in range(len(self.pixels)):
                line += "%02x" % self.pixels[i].r
            print line
            time.sleep(0.002)


class KittEffect(object):
    def __init__(self, lights):
        self.lights = lights
        self.pos = 0
        self.vector = 1
        self.brightness = [0] * len(lights.pixels)
        self.fade_speed = 16

    def step(self):
        if self.pos >= len(self.brightness)-1:
            self.pos = len(self.brightness) - 1
            self.vector = -1

        if self.pos <= 0:
            self.pos = 0
            self.vector = 1

        self.pos += self.vector

        for i,v in enumerate(self.brightness):
            if v > self.fade_speed:
                self.brightness[i] -= self.fade_speed
            else:
                self.brightness[i] = 0

        self.brightness[self.pos] = 255

        for i,v in enumerate(self.brightness):
            self.lights.set(i, Color(v,0,0))

        self.lights.render()

    def loop(self):
        while True:
            self.step()
            time.sleep(0.05)


lights = Lights(40, "screen")
kitt = KittEffect(lights)
kitt.loop()