Read a color pattern line at position
        :param pos: pattern line to read
        :return pattern line data as tuple (r,g,b, step_millis)

def readPatternLine(self, pos):
        """Read a color pattern line at position
        :param pos: pattern line to read
        :return pattern line data as tuple (r,g,b, step_millis)
        """
        if ( self.dev == None ): return ''
        buf = [REPORT_ID, ord('R'), 0, 0, 0, 0, 0, int(pos), 0]
        self.write(buf)
        buf = self.read()
        (r,g,b) = (buf[2],buf[3],buf[4])
        step_millis = ((buf[5] << 8) | buf[6]) * 10
        return (r,g,b,step_millis)