The Design For Wireless Multiple Measuring System Of Temperature And Humidity Based On NRF24E1

What this text studied is a concrete application of the wireless shortdistance communication technology in temperature and humidity measures,main introduction the design thought and implement method of the multiplewireless short distance measuring system of temperature and humidity basedon the single chip radio transceiver nRF24E1. With embeded MCU-51 kernelof the RF transceiver chip nRF24E1 as the core system, adopt digitaltemperature sensor DS18B20 and analog humidity sensor HM1500 , usessensing technology , wireless receive and transmitte technology and computertechnology , realize the acquisition of multiple temperature and humidity dataand short distance wireless transmitted.The wireless multiple measuring systems of temperature and humiditybased on nRF24E1 is formed by two major parts mainly : First part is theslave's of the system, with a radio transceiver -nRF24E1 chip as the core ,make up temperature and humidity acquisition network with many chips oftemperature & humidity sensor, complete the acquisition of multipletemperature & humidity data and transmitte them wirelessly. Second part is thehost of the system, with a radio transceiver -nRF24E1 chip as the managementunit, through expanding interface module such as display , keyboard ,RS232 ,etc. , achieve the wireless receiving , display and uploading function oftemperature & humidity data.The single chip radio transceiver nRF24E1 is adopted for temperature andhumidity data wireless transmission which made from Nordic VLSI Companyof Norway. Regard nRF2401 chip as the core, nRF24E1 is integrated with RFreceiving and transmission, GMSK modulation and demodulation ,enhancement 8051 kernel , 9 input 12bit ADC , 125 channel , UART , SPI ,PWM , RTC , WDT all among in the single chip, few peripheral circuit, thehigh-frequency components are all integrated within the chip, performance issteady and could't interfered by the external electromagnetic interfere.Compared with bluetooth, nRF24E1 have no complicated communicationprotocol, totally transparent to users, the same kind of product can freecommunication, all working parameter can set up finishing through thesoftware. Integrated 51 enhanced kernels within nRF24E1, needn't dispose theMCU alone , has already simplified the design of circuit, improve systematicanti-interference ability, so,nRF24E1 is the low cost RF system chip withsmall volume, lower consumption, few external components. While usingnRF24E1, we need set up the relevant configuration in the system.Theconfiguration word is downloaded to nRF2401 subsystem through a simple3-wires interface (CS , CLK1 and DATA ) . The configuration word config thereceiving address of the radio transceiver, the frequency of receiving andtransmission, RF output power , RF data rate, communication mode , and CRCcheck-up length and the length of data payload. In the same moment, radiotransceiver can only at receiving or sending mode, generally regard thereceiving mode as the awaiting state . There is only ShockBurst mode beconfiged at the receiving and transimission mode in nRF2401 subsystemwithin nRF24E1. It is an important part of the communication protocol that thedata packet the form , the intact radio frequency data packet are setted up offour parts: Preamble , address , payload and CRC. CRC can be addedautomatically by built-in CRC hardware circuit, can be setted as 0 , 8 or 16 bit,preamble , address and CRC are all moved automatically after the receiverreceive the data packet , only keep the payload. When using CRCcharacteristic in nRF2401 subsystem , pay attention to CRC already beenabled, and use the same length at the transmitter and receiver. The acquisition port of the temperature data has adopted the digitalintegrated single-bus made temperature sensor DS18B20 from Dallassemiconductor Company of U.S.A.. With unique single-bus interface ,it canconnect several dozen digital sensors on a signal line, it is very simple toconnect with the interface of the microprocessor, very suitable for themeasurement of temperature distributedly, make circuit structural design andhardware expenses of this system greatly simplify. The output of DS18B20 isdigital, overcoming the shortcomings of needing A/D converter and othercomplicated external circuit while the analog temperature sensor connectedwith microprocessor interface , and it only takes up a I/O port of themicroprocessor, so, are especially suitable for the lacking system ofmicroprocessor I/O port resources. DS18B20 has CRC check-up function,dependability is high. Because every DS18B20 have only one sequencenumber and be recorded in the ROM when manufactured from the factory, soCPU can be identifed with the simple communication protocol, thus save alarge number of lead wire and logical circuit Utilizing the characteristic of multiple A/D converters within nRF24E1,adopting the voltage-output integrated humidity sensor HM1500 which madefrom Humirel Company of France as the humidity data acquisition port of thesystem. HM1500 humidity sensor integrates the contact-type humid capacitnceHS1101 and humidity signal modulator in single chip , the integrated level ishigh, does not need peripheral component , it is very convenient to use. Main...