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《Transactions of The Chinese Society of Agricultural Engineering》 2005-11
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Bus network topology for environmental control of protected agriculture

Wang Fengyun~1,Zhu Jianhua~1,Zhao Yimin~2,Shang Minghua~1,Feng Wenjie~1 (1.Information Engineering Technological Research Center,Shandong Academy of Agricultural Sciences,Jinan 250100,China;2.Quality Assurance Department of Shandong Shengli Co.,Ltd.,Jinan 250101,China)  
With the development of protected agriculture,the size of environment control system is larger and larger.The RS-485 bus has the virtues of simpleness,convenience to use,appropriate distance of communication,proper rate of transmission and high(reliability).It is widely used in the control of agricultural environment.But TIA EIA-485 stipulates that an RS-485 connection has no more than 32 noads.To solve the problem of more than 32 nodes in the communication network,a method of RS-485 bus topology based on single chip is put forward in the paper.The method adds the capacity of RS-485 bus.The bus network can extend to four,eight and twelve branches according to the concrete case.The design is simple and the cost is low.The circuit runs smoothly and(reliably).
【Fund】: 国家863计划项目(2003AA209070)
【CateGory Index】: X84;
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