外文文献资料 The System Design of Wireless Basketball Timer Based on MCU and NRF24L01 Abstract: Currently, Basketball players must know the progress well in time in the game, the presence of electronic timer with LED display influences the basketball games. The wired operation influences the control distance, control reliability, control efficiency and so on. So how to make it longer, anti-interference, easy operation and high efficiency is a difficult problem. A kind of wireless basketball timer is designed based on micro-computer unit (MCU) and wireless nRF24L01 module to compensate for the existing disadvantages, which has LED digital tube of large size for the section number display and middle size for game display and 24s display.The user is easy to carry and control the timer wirelessly at any place in the basketball court using the sending control device. The test results show that the system, easy to control and stable to operate, is reliable to transmit the wireless data. Keywords: Basketball timer, MCU , nRF24L01 , system design , wireless communication 1. INTRODUCTION In the current basketball games, players need to know 24 sec and the remaining time of each period match in time; electronic timer with the advantages of its convenient operation, compact size and visualization has been widely used in basketball games. NBA timing and score system was designed by a chip called 8031 of MCS-51.The system consists of time counting, score counting, keyboards and display sub-systems (Luo-Sheng, 2004). A new timing and scoring equipment for basketball match was designed and made by Chinese Basketball Association, used in 2004 CBA league match and NBA in Beijing, which was helpful for the present timing and scoring equipment specialized in sport venues and has great room for development and application (Zhang et al., 2006).The control system of basketball scoreboard with 16*16 matrix LED was designed based on single-chip microcomputer, which could be off-line and continuous long-term operation and so on (Wei-Yu et al., 2008).The design of hardware and software of timing-score system was achieved using 89C51, which had the functions of the total time and the total countdown, with its features of modular design, simple process structure, clear mandate and easy to prepare (Han et al., 2009).The device was based on P89V51RB2 single-chip microcomputer, which can show the current section, the remaining time and the score, according to actual situations, the time and score can be amended (Rong-Jian et al., 2010).The countdown circuit was designed based on STC89C52 single-chip microcomputer, which can countdown 999 days, accurate to seconds. The result of the experiment demonstrates the correctness and feasibility of the design (Ze-Shi, 2011).Although these timer or score systems are convenient to use, there are some disadvantages during the use of them, some are inconvenient for both players as a result of small size and the position of use and some are inconvenient to install and repair and low efficiency and reliability and so on, because of the long cable connect of between sending device and receiving device.In the current Chinese market, a electronic timer includes a sending device which can be moved and a receiving device which is fixed on or over the basketball frame, can provide real-time information of time for players and audiences.Still it is easy to cause bad connect because of the frequent connect of sending device and receiving device.In the basketball game, the basketball referee can need to move frequently, which is away from the sending device and cannot carry it due to the wire and must pass some information about the game to the live operator operating the sending device, which can lead to inaccurate and no timely information.According to the above reasons, a system based on MCU and wireless chip can be put forward which can send the information wirelessly and easy to carry, etc.2. BASKETBALL TIMER Basketball timer is an indispensable instrument in basketball games, which used to show the information of time and quarter of the game.In addition, in order to accelerate the game, players should shoot at the basket within 24 sec, otherwise it will break the rule. In common, basket timer is connected with receiver from transmitter by RS232 serial.However, the electric cables are fragile and difficult to operate.So, wireless data transmission is a better choice. Some short distance wireless data communication such as Bluetooth, Zigbee, Wi-Fi that work on 2.4GHz, but these technologies are complicated and cost more, it is difficult to meet the rapid development and low cost requirement in general applications.nRF24L01 module is a new single chip RF transceiver device launched by Norway Nordic Semiconductor, built-in frequency synthesizer, a power amplifier, a crystal oscillator, a modulator module (Zhang et al., 2004) and fused with enhanced Shock Burst technology, with advantages of