Analysis of Application of Wireless Sensor Network Node Technology
2023-04-03 08:11:00
The wireless sensor network node is a miniature embedded system, which has the functions of collecting, sending, and receiving data. This paper designs a network receiving node based on wireless communication technology and adopts a RF receiving chip T5743 network receiving node to achieve the data of the network node. Receiving at a short distance, and reducing the bit error rate of the received data to realize sensor data wireless communication.
I. Introduction
Wireless sensor networks deploy hundreds or thousands of sensor nodes in a specific area to form a monitoring network. These nodes are efficiently, stably, and correctly organized through specific protocols and work together to complete an application task to achieve data acquisition and wireless communication. And information processing capabilities. The wireless sensor network node can transmit monitoring data in real time, has the characteristics of rapid construction and deployment, and is not easily constrained by the target environment. Therefore, it has good applications in environmental monitoring, urban traffic management, medical monitoring, warehouse management, automotive electronics and other fields. .
The node in the wireless sensor network is usually a miniature embedded system. The functional requirements for collecting data, receiving data, processing data, and sending data are all taken into consideration. The processing capability, storage capacity, and communication capability are all collected. Data management and collaborative work, so sensor network node hardware and software technology is the focus of sensor network research. This paper mainly discusses the design of short-range receivers for wireless sensor network node data.
Second, the receiving node works
The wireless sensor network data receiving node module is mainly composed of a receiving chip T5743 and an MCU microprocessor PIC18F6620. As shown in FIG. 1, the transmitting end uses ATMEL's T5754 as a data transmitting chip, and is matched with a receiving chip T5743 to receive a certain transmission. Frequency and data transmission rate work together. The receiving chip T5743 communicates with the I/O port of the MCU microprocessor PIC18F6620 through the DATA serial bidirectional data line. When the MCU microprocessor receives data, it uses the DATA_CLK as the synchronization clock, and the microprocessor PIC18F6620 relies on the instructions sent to the receiving chip T5743. Special timing to achieve data reception and processing. The receiving process uses software control to carry out data transmission and control of the receiving chip T5743. Before receiving the data, the microprocessor PIC18F6620 writes the program in the MUC into the configuration register of the receiving chip through the DATA line and performs the process on the receiving chip. Configuration, and then wait to receive data; When there is data, it is accessed by the LNA_IN terminal of the receiving chip T5743, amplified by the low noise amplifier and sent to the mixer to transform it into an intermediate frequency; at the intermediate frequency level, the transformed signal is It is amplified and filtered before it is sent to the demodulator.
Third, the receiving node chip
ATMEL's T5743 chip is an integrated UHF radio receiver module with a phase-locked loop (PLL) receiver chip in the SO20 package. The T5743 chip is developed to meet the requirements of a low data rate, low-cost RF data transmission system. The data transmission speed is 1 to 10 kB/s, and the encoding method is Manchester or dual-phase, which can be used in the receiving frequency range. ASK data transmission from 300MHz to 450MHz (433.92MHz and 315MHz); High-sensitivity, fully-integrated VCO for low power consumption, supply voltage 4.5V~5.5V; Single-ended RF output easily printed with antenna or PCB board The antenna is adapted; the operating temperature range is -40°C to 105°C.
T5743 chip has a bidirectional serial data interface DATA, through DATA chip can carry on serial communication with MCU, exchange information. It can work in two typical frequencies 433.92MHz and 315MHz. It is selected by the MODE pin. It is set to 433.92MHz, set to 315MHz, and the receive frequency is between 1kB and 10kB. It is set by software. Designed to achieve high image rejection due to the use of 1MHz IF and front-end SAW filters, based on the new SAW device, achieving 40dB rejection and enabling communication with the microcontroller using a simple bidirectional data line, using separate pins Microcontrollers implement power management.
The RF front end of the T5743 chip is a superheterodyne structure that converts the RF input signal to a 1MHz IF signal. The RF front-end consists of a low-noise amplifier LNA, a local oscillator LO, a mixer, and an RF amplifier. The LO is the carrier frequency generated by the PLL phase-locked loop for use by the mixer. The RF signal is input via the RF input pin LNA-IN, and the input impedance is 1000Ω/pF at 433.92MHz. The noise matching is first considered when designing the input network, and the component values ​​and the distributed inductance and capacitance of the printed circuit board are properly adjusted to match the input. T5743 has the highest sensitivity at high SNR. In this way, the signal from the RF front-end is filtered by a fully-integrated fourth-order IF filter to reach 334.99.2 MHz, and the center frequency of the IF is 1 MHz.
The mode of operation of the demodulator in the design is set by the register OPMODE. The logic “L†sets the demodulator to FSK mode; the logic “H†sets the demodulator to ASK mode. An automatic threshold control circuit is used in the ASK mode, which sets the detection reference voltage at an appropriate value for good signal-to-noise ratio. This circuit can also effectively suppress any type of in-band noise signal or competition emission if the S/N More than 10dB can detect the data signal well. In FSK mode, digital signals can be detected if S/N exceeds 2dB.
The demodulator output signal is filtered by the digital filter and sent to the digital signal processing circuit. The passband of the digital filter matches the characteristics of the data signal. The digital filter consists of first-order high-pass and third-order low-pass filters. The cutoff frequency fcu_DF of the high-pass filter is determined by formula (1). The cut-off frequency of the low-pass filter is determined by the selected baud rate range (BR-Range), BR-Range is set in the OPMODE register, and the BR-Range setting must be compatible with the baud rate.
All the timing of the digital circuit and analog filter of the wireless sensor network receiving node comes from one clock. This clock period, TCLK, is derived from the crystal oscillator via a divider. The number of divisions is controlled by the logic state at the MODE pin. The frequency of the crystal oscillator is determined by the RF input signal, which also determines the local oscillator frequency (fLO). The working state of the T5743 chip is set by two 15-bit RAM registers, OPMODE and LIMIT, and the register can be programmed by the bidirectional DATA port. If the contents of the register change due to power loss, this state is indicated by an output called the reset flag (RM), in which case the receiver circuit must be reprogrammed. After power-on reset (POR), the register is set to the default mode. If the receiver operates in the default mode, the register does not need to be programmed. Similarly, if the receiving circuit is not in the reset mode, it will initiate the corresponding OFF instruction programming; if the receiving circuit is in the reset mode, the corresponding OFF instruction programming will not be started, and the DATA pin still shows the reset flag.
Fourth, receiving node circuit
The wireless sensor network receiving node chip T5743 is a highly integrated PLL wireless receiving module capable of receiving and demodulating FSK-modulated Manchester encoded data and sending it out through a bidirectional data port. The wireless receiver chip uses a smart polling mode to make the receiving node stay in sleep mode most of the time. Only when it detects effective transmission, it will end the sleep mode to receive mode and send the data stream to the controller. In this way, energy consumption can be minimized. Figure 2 shows the schematic of the wireless receiving node circuit.
The XTO of T5743 of the receiving chip of Fig. 2 is the input end of the reference crystal, the pin LNA_IN provides RF to LNA input, the designed receiving frequency is 433.92MHz, so fXTO = 6.76438MHz, set the MODE pin to high level, The data clock cycle TCLK is 2.0697 μs. The DATA pin is connected to the RB0 pin, the DATA_CLK pin is connected to the RB2 pin, the POLLING pin is connected to the RC7 pin, and the IC_ACTIVE pin is connected to the RF1 pin. This completes the connection between the T5743 and the MCU microprocessor PIC18F6620.
The LF pin of the T5743 of the receiver chip is connected to a passive loop filter with a bandwidth of 100 kHz. The inductance L of LNA_GND pin is 25nH, L is the feed inductance, in order to establish the power DC passage. C7 and L together form a series resonant circuit. The LNA_IN pin is connected to the antenna and the middle part is a T-type matching network.
V. Data transmission error rate test
The validity of the data received by the receiving node of the wireless sensor network must be verified by verifying the performance of the system. When the system communication test is performed within a certain distance, the reliability and validity of the data transmission are judged. After the T5743 chip of the network receiving node completes the timing detection of the input and output waveforms and the circuit logic, the wireless network receiving node is connected with the PC, and the distance between the transmitting end and the receiving end is changed, and the communication distance and the corresponding bit error rate are tested. . In the design, the transmitting end sends the test data of 20062120133-20062240266 uniformly increasing at a data rate of 5kB. The error code test program synchronizes the received data with its own generated data sequence (20062120133-20062240266) and compares the measured bit error rate. Table 1 shows the data bit error rate test result of the receiving node.
In the communication distance and communication error rate test process, external interference has little impact on the system in the communication distance of 5m to 10m, even artificially manufactured electromagnetic interference has a small impact on its communication error rate, and the receiving node can be stable and effective. Work; 10m ~ 30m communication distance, external interference has a greater impact on the system, the receiving node communication error rate rises, but can still meet the communication requirements, the receiving node performance between the occurrence of instability or instability; more than 30m above the system work instability The communication error rate rises quickly and the receiving node can no longer meet the communication data transmission requirements.
Sixth, the conclusion
The wireless sensor network designs the network receiving node based on the wireless communication technology, adopts the RF data receiving chip T5743 to receive the data collected by the sensor, and processes the received data through the MCU microprocessor PIC18F6620 to realize the wireless network data transmission. This design realizes the wireless reception of the data collected by the sensor, and can effectively and accurately receive data in short-range wireless communication and reduce the occurrence of bit error rate.
I. Introduction
Wireless sensor networks deploy hundreds or thousands of sensor nodes in a specific area to form a monitoring network. These nodes are efficiently, stably, and correctly organized through specific protocols and work together to complete an application task to achieve data acquisition and wireless communication. And information processing capabilities. The wireless sensor network node can transmit monitoring data in real time, has the characteristics of rapid construction and deployment, and is not easily constrained by the target environment. Therefore, it has good applications in environmental monitoring, urban traffic management, medical monitoring, warehouse management, automotive electronics and other fields. .
The node in the wireless sensor network is usually a miniature embedded system. The functional requirements for collecting data, receiving data, processing data, and sending data are all taken into consideration. The processing capability, storage capacity, and communication capability are all collected. Data management and collaborative work, so sensor network node hardware and software technology is the focus of sensor network research. This paper mainly discusses the design of short-range receivers for wireless sensor network node data.
Second, the receiving node works
The wireless sensor network data receiving node module is mainly composed of a receiving chip T5743 and an MCU microprocessor PIC18F6620. As shown in FIG. 1, the transmitting end uses ATMEL's T5754 as a data transmitting chip, and is matched with a receiving chip T5743 to receive a certain transmission. Frequency and data transmission rate work together. The receiving chip T5743 communicates with the I/O port of the MCU microprocessor PIC18F6620 through the DATA serial bidirectional data line. When the MCU microprocessor receives data, it uses the DATA_CLK as the synchronization clock, and the microprocessor PIC18F6620 relies on the instructions sent to the receiving chip T5743. Special timing to achieve data reception and processing. The receiving process uses software control to carry out data transmission and control of the receiving chip T5743. Before receiving the data, the microprocessor PIC18F6620 writes the program in the MUC into the configuration register of the receiving chip through the DATA line and performs the process on the receiving chip. Configuration, and then wait to receive data; When there is data, it is accessed by the LNA_IN terminal of the receiving chip T5743, amplified by the low noise amplifier and sent to the mixer to transform it into an intermediate frequency; at the intermediate frequency level, the transformed signal is It is amplified and filtered before it is sent to the demodulator.
Third, the receiving node chip
ATMEL's T5743 chip is an integrated UHF radio receiver module with a phase-locked loop (PLL) receiver chip in the SO20 package. The T5743 chip is developed to meet the requirements of a low data rate, low-cost RF data transmission system. The data transmission speed is 1 to 10 kB/s, and the encoding method is Manchester or dual-phase, which can be used in the receiving frequency range. ASK data transmission from 300MHz to 450MHz (433.92MHz and 315MHz); High-sensitivity, fully-integrated VCO for low power consumption, supply voltage 4.5V~5.5V; Single-ended RF output easily printed with antenna or PCB board The antenna is adapted; the operating temperature range is -40°C to 105°C.
T5743 chip has a bidirectional serial data interface DATA, through DATA chip can carry on serial communication with MCU, exchange information. It can work in two typical frequencies 433.92MHz and 315MHz. It is selected by the MODE pin. It is set to 433.92MHz, set to 315MHz, and the receive frequency is between 1kB and 10kB. It is set by software. Designed to achieve high image rejection due to the use of 1MHz IF and front-end SAW filters, based on the new SAW device, achieving 40dB rejection and enabling communication with the microcontroller using a simple bidirectional data line, using separate pins Microcontrollers implement power management.
The RF front end of the T5743 chip is a superheterodyne structure that converts the RF input signal to a 1MHz IF signal. The RF front-end consists of a low-noise amplifier LNA, a local oscillator LO, a mixer, and an RF amplifier. The LO is the carrier frequency generated by the PLL phase-locked loop for use by the mixer. The RF signal is input via the RF input pin LNA-IN, and the input impedance is 1000Ω/pF at 433.92MHz. The noise matching is first considered when designing the input network, and the component values ​​and the distributed inductance and capacitance of the printed circuit board are properly adjusted to match the input. T5743 has the highest sensitivity at high SNR. In this way, the signal from the RF front-end is filtered by a fully-integrated fourth-order IF filter to reach 334.99.2 MHz, and the center frequency of the IF is 1 MHz.
The mode of operation of the demodulator in the design is set by the register OPMODE. The logic “L†sets the demodulator to FSK mode; the logic “H†sets the demodulator to ASK mode. An automatic threshold control circuit is used in the ASK mode, which sets the detection reference voltage at an appropriate value for good signal-to-noise ratio. This circuit can also effectively suppress any type of in-band noise signal or competition emission if the S/N More than 10dB can detect the data signal well. In FSK mode, digital signals can be detected if S/N exceeds 2dB.
The demodulator output signal is filtered by the digital filter and sent to the digital signal processing circuit. The passband of the digital filter matches the characteristics of the data signal. The digital filter consists of first-order high-pass and third-order low-pass filters. The cutoff frequency fcu_DF of the high-pass filter is determined by formula (1). The cut-off frequency of the low-pass filter is determined by the selected baud rate range (BR-Range), BR-Range is set in the OPMODE register, and the BR-Range setting must be compatible with the baud rate.
All the timing of the digital circuit and analog filter of the wireless sensor network receiving node comes from one clock. This clock period, TCLK, is derived from the crystal oscillator via a divider. The number of divisions is controlled by the logic state at the MODE pin. The frequency of the crystal oscillator is determined by the RF input signal, which also determines the local oscillator frequency (fLO). The working state of the T5743 chip is set by two 15-bit RAM registers, OPMODE and LIMIT, and the register can be programmed by the bidirectional DATA port. If the contents of the register change due to power loss, this state is indicated by an output called the reset flag (RM), in which case the receiver circuit must be reprogrammed. After power-on reset (POR), the register is set to the default mode. If the receiver operates in the default mode, the register does not need to be programmed. Similarly, if the receiving circuit is not in the reset mode, it will initiate the corresponding OFF instruction programming; if the receiving circuit is in the reset mode, the corresponding OFF instruction programming will not be started, and the DATA pin still shows the reset flag.
Fourth, receiving node circuit
The wireless sensor network receiving node chip T5743 is a highly integrated PLL wireless receiving module capable of receiving and demodulating FSK-modulated Manchester encoded data and sending it out through a bidirectional data port. The wireless receiver chip uses a smart polling mode to make the receiving node stay in sleep mode most of the time. Only when it detects effective transmission, it will end the sleep mode to receive mode and send the data stream to the controller. In this way, energy consumption can be minimized. Figure 2 shows the schematic of the wireless receiving node circuit.
The XTO of T5743 of the receiving chip of Fig. 2 is the input end of the reference crystal, the pin LNA_IN provides RF to LNA input, the designed receiving frequency is 433.92MHz, so fXTO = 6.76438MHz, set the MODE pin to high level, The data clock cycle TCLK is 2.0697 μs. The DATA pin is connected to the RB0 pin, the DATA_CLK pin is connected to the RB2 pin, the POLLING pin is connected to the RC7 pin, and the IC_ACTIVE pin is connected to the RF1 pin. This completes the connection between the T5743 and the MCU microprocessor PIC18F6620.
The LF pin of the T5743 of the receiver chip is connected to a passive loop filter with a bandwidth of 100 kHz. The inductance L of LNA_GND pin is 25nH, L is the feed inductance, in order to establish the power DC passage. C7 and L together form a series resonant circuit. The LNA_IN pin is connected to the antenna and the middle part is a T-type matching network.
V. Data transmission error rate test
The validity of the data received by the receiving node of the wireless sensor network must be verified by verifying the performance of the system. When the system communication test is performed within a certain distance, the reliability and validity of the data transmission are judged. After the T5743 chip of the network receiving node completes the timing detection of the input and output waveforms and the circuit logic, the wireless network receiving node is connected with the PC, and the distance between the transmitting end and the receiving end is changed, and the communication distance and the corresponding bit error rate are tested. . In the design, the transmitting end sends the test data of 20062120133-20062240266 uniformly increasing at a data rate of 5kB. The error code test program synchronizes the received data with its own generated data sequence (20062120133-20062240266) and compares the measured bit error rate. Table 1 shows the data bit error rate test result of the receiving node.
In the communication distance and communication error rate test process, external interference has little impact on the system in the communication distance of 5m to 10m, even artificially manufactured electromagnetic interference has a small impact on its communication error rate, and the receiving node can be stable and effective. Work; 10m ~ 30m communication distance, external interference has a greater impact on the system, the receiving node communication error rate rises, but can still meet the communication requirements, the receiving node performance between the occurrence of instability or instability; more than 30m above the system work instability The communication error rate rises quickly and the receiving node can no longer meet the communication data transmission requirements.
Sixth, the conclusion
The wireless sensor network designs the network receiving node based on the wireless communication technology, adopts the RF data receiving chip T5743 to receive the data collected by the sensor, and processes the received data through the MCU microprocessor PIC18F6620 to realize the wireless network data transmission. This design realizes the wireless reception of the data collected by the sensor, and can effectively and accurately receive data in short-range wireless communication and reduce the occurrence of bit error rate.
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