Play internal color pattern
        :param start_pos: pattern line to start from
        :param end_pos: pattern line to end at 
        :param count: number of times to play, 0=play forever

def play(self, start_pos=0, end_pos=0, count=0):
        """Play internal color pattern
        :param start_pos: pattern line to start from
        :param end_pos: pattern line to end at 
        :param count: number of times to play, 0=play forever
        """
        if ( self.dev == None ): return ''
        buf = [REPORT_ID, ord('p'), 1, int(start_pos), int(end_pos), int(count), 0, 0, 0]
        return self.write(buf);