tardis

tardis.py

#!/usr/bin/env python

import spidev
import time
import math

speed = 1000000
bpw = 8

spi = spidev.SpiDev()
spi.open(0,0)
spi.bits_per_word = bpw
spi.lsbfirst = False
spi.mode = 0
spi.max_speed_hz = speed

count = 250

limit = math.pi * 2.0
incr = math.pi / 64
step = 0

fadeat = 100
faderange = 60.0
fadeback = 300.0

fadecount = 0
fadeamount = 1.0

while True:
	p = []
	for i in range(count):
		if i < count * 0.98:
			p.append(0)
			p.append(0)
			p.append(int(fadeamount * 255.0))
		else:
			v = int((math.sin(step) + 1) * 127.0 * fadeamount)
			p.append(v)
			p.append(v)
			p.append(v)

	spi.xfer2(p, speed, 500, bpw)

	step += incr
	if step > limit:
		step = 0

	fadecount += 1
	if fadecount > fadeat:
		fadeamount = 1.0 - ((fadecount - fadeat) / faderange)
		if fadeamount < 0.0:
			fadeamount = 0.0

	if fadecount > fadeback:
		fadeamount = (fadecount - fadeback) / faderange
		if fadeamount > 1.0:
			fadeamount = 1.0
			fadecount = 0
		
	time.sleep(0.01)