def writePatternLine(self, step_milliseconds, color, pos, led_number=0):
        """Write a color & step time color pattern line to RAM 
        :param step_milliseconds: how long for this pattern line to take
        :param color: LED color
        :param pos: color pattern line number (0-15)
        :param led_number: LED to adjust, 0=all, 1=LEDA, 2=LEDB
        """
        if ( self.dev == None ): return ''
        self.setLedN(led_number)
        red, green, blue = self.color_to_rgb(color)
        r, g, b = self.cc(red, green, blue)
        step_time = int(step_milliseconds / 10)
        th = (step_time & 0xff00) >> 8
        tl = step_time & 0x00ff
        buf = [REPORT_ID, ord('P'), int(r), int(g), int(b), th,tl, pos, 0]
        return self.write(buf);