#!/usr/bin/python
 
import spidev

spi = spidev.SpiDev()
spi.open(0,0)
spi.max_speed_hz=1000000


def readChannel(channel):
  val = spi.xfer2([1,(8+channel)<<4,0])
  data = ((val[1]&3) << 8) + val[2]
  return data
  
if __name__ == "__main__":
  v=(readChannel(0)/1023.0)*3.3
  dist = 16.2537 * v**4 - 129.893 * v**3 + 382.268 * v**2 - 512.611 * v + 301.439
  print "Distanz: %.2f cm" % dist