Wireless sensor networks (WSNs) are networks composed of a large number of miniature sensor nodes that operate wirelessly and self-organizing. They integrate sensor, microelectromechanical, and wireless communication technologies, enabling real-time sensing, acquisition, and processing of object information within the network's coverage area, and transmitting this information to observers. WSNs offer advantages such as wide coverage, remote monitoring, high monitoring accuracy, rapid deployment, and low cost, making them promising candidates for applications in military, environmental protection, healthcare, space exploration, industrial monitoring, and precision agriculture. 1. Wireless Sensor Network Structure As shown in Figure 1, a typical WSN system includes several sensor terminal nodes, a sink node, and a set of backend monitoring software. The sensor terminal nodes have dual functions: local data acquisition and transmission, and forwarding data from neighboring nodes. They can acquire data under the control of the backend management software and the sink node, and transmit the data to the sink node via multi-hop routing. The sink node is the center of the network, acting as a coordinator and gateway, responsible for network configuration, management, data aggregation, and communication with the user's PC backend management software. 2. System Hardware Design The hardware of a WSN terminal node generally includes a processing unit, a wireless transmission unit, a sensor acquisition unit, and a power supply unit. The design comprises a processing unit responsible for controlling the operation of sensor nodes and storing and processing data; a sensing and acquisition unit responsible for collecting information within the monitoring area; a wireless transmission unit responsible for wireless communication between nodes; and a power supply unit responsible for powering the nodes. The Sink node has more functions, including the aforementioned functional units as well as an interface unit for communication with the background monitoring software. This paper uses a serial port as the communication interface between the Sink node and the background monitoring software. In this design, the processing unit uses the TI 16-bit low-power microcontroller MSP430F1611, the wireless transmission unit uses the low-power wireless transceiver module CC1100, the sensing and acquisition unit uses the temperature and humidity sensor DHT90, and the power supply module uses two ordinary AAA batteries. Furthermore, considering the time correlation of much data, this design also includes a time control unit composed of a real-time clock DS1337. The node composition is shown in Figure 2, and the actual node diagram is shown in Figure 3. 2.1 The outstanding feature of the MSP430F1611 processing unit is its extremely low power consumption. It has five programmable operating modes, with an operating current of only 280μA in active mode and only 0.1 μA in LPM4 mode. The MSP30F1611 has 44 KB of Flash memory and 10 KB of RAM, as well as a rich set of peripherals. In this paper, the MSP430F1611 uses an I2C interface to connect to the RTC, an SPI interface to connect to the wireless transceiver module, and a UART interface to connect to the serial communication unit. 2.2 Wireless Transceiver Unit The wireless transceiver unit uses the Chipcon CC1100 RF chip. This chip is small in size, low in power consumption, supports programmable control of data rates from 1.2 to 500 kbps, and can operate in four bands: 915 MHz, 868 MHz, 433 MHz, and 315 MHz, providing output power from -30 to 10 dBm in all bands. In this paper, the CC1100 operates at a frequency of 433 MHz, using FSK modulation, with a data rate of 100 kbps and a channel spacing of 200 kHz. The CC1100 is connected to the microcontroller via an SPI interface, as shown in Figure 4. SPI bus interface technology is a high-speed, high-efficiency serial interface technology, mainly used for expanding peripherals and exchanging data. The following is an example code for communicating with MSP430F1611 using SPI. (1) Write a value to the specified register of CC1100 (2) Read a single register value Figures 5 and 6 are flowcharts of data transmission and reception using CC1100. 2.3 Data Acquisition Unit The data acquisition unit of the node can select a suitable sensor according to actual needs and the characteristics of the monitored physical signal, such as light, pressure, vibration, temperature, humidity, soil salinity, etc. The data acquisition unit of this paper uses Sensirion's digital temperature and humidity sensor DHT90. DHT90 integrates temperature/humidity sensor, signal amplifier and conditioner, A/D converter and bus interface, and can perform fully calibrated digital output. It can directly provide digital output with a temperature range of -40℃ to 120℃ and a resolution of 14 bits, and a humidity range of 0 to 100%RH and a resolution of 12 bits. 2.4 Time Control Unit The time control unit is used to set and record the data acquisition time so that the background user can process the data based on the acquisition time. This paper selects the Maxim Integrated DS1337 serial real-time clock chip as the time control unit. The DS1337 can operate from 1.8 to 5.5 V and has very low power consumption, requiring only 15 μA in sleep mode. 2.5 Power Supply Unit This paper uses two AAA alkaline Nanfu batteries to power the entire node. In order to obtain the node's battery power status in a timely manner and adjust the node's communication status according to the remaining battery power and discharge characteristics, this paper uses the ADC12 module integrated in the MSP430F1611 chip to measure the positive voltage level of the power supply. By comparing the measured voltage level with the reference voltage level, the converted data NADC is obtained. Finally, the power supply voltage Vin can be obtained by the following formula: Where: VR+ is the positive reference voltage, VR- is the negative reference voltage, Vin is the voltage value converted by ADC12, and NADC is the value of the microcontroller's conversion register. 2.6 Serial Communication Unit Only the Sink node in the network contains a serial communication unit; terminal nodes do not require one. The Sink node's processing unit, MSP430F1611, communicates with the background monitoring host via the serial communication unit. The Sink node can transmit the collected network information data to the background monitoring host through the serial communication module. Researchers then publish data and commands to the sensor network based on the intelligent processing results of the collected data by the monitoring software. 3. Protocol Software Design 3.1 Topology The first step in formulating the network protocol is to determine the network topology. The wireless sensor network protocol designed in this paper adopts a cluster-tree topology. A cluster-tree topology is a tree-like topology generated by a network coordinator, suitable for situations where nodes are stationary or move minimally; it does not require storing routing tables and has advantages such as low routing algorithm complexity and no initial delay. 3.2 Communication Protocol Stack The purpose of designing the wireless communication protocol is to separate the specific communication mechanism from the upper-layer application, providing network communication functionality for sensor nodes. To reduce the complexity of network design, a layered design is adopted, referencing the OSI model, dividing the entire protocol into four layers: the physical layer, providing simple yet robust signal modulation and wireless transceiver technology; the MAC layer, responsible for data framing, frame detection, media access, and error control; the network layer, primarily responsible for route generation and routing; and the application layer, including a series of application layer software based on monitoring tasks. The system communication protocol architecture is shown in Figure 7. The entire system protocol design includes the sink node protocol design and the terminal node protocol design. Due to space limitations, this paper only introduces the terminal node software protocol and the system main program. As shown in Figure 8, after successful initialization, the terminal node enters the channel scanning and listening state. When it detects activity from a neighboring node, it requests a time stamp frame from the neighboring node. The node synchronizes its clock according to the received time stamp frame. After clock synchronization, the node enters the access state. After successful access, the node enters the service state. In the service state, the node executes commands issued by the background and the sink node, performs data sensing and acquisition, transmission, and relay forwarding of data from neighboring nodes. To achieve low power consumption, the node must alternate between the service state and the sleep state. 4. System Energy Saving Energy saving is a top priority in the design of the entire network system. Energy saving relies on two aspects: the low power consumption of the hardware system itself and the low power consumption of the software protocol. On the hardware side, this paper selects low-power chips for the nodes, and the board layout fully considers low power requirements. On the software side, in addition to employing a sleep mechanism, a routing protocol based on a battery energy model is also used, enabling nodes to operate according to battery energy characteristics, thereby extending battery life. Conclusion This paper mainly introduces a hardware and software design scheme for a wireless sensor network based on the MSP430F1611 microcontroller and CC1100 wireless transceiver module, capable of accurately collecting environmental temperature and humidity information. In actual network testing, a demonstration system with 19 terminal nodes and 1 sink node was built. Nodes wake up every two hours from sleep, collect data, and send it to the observer. Experiments show that the wireless sensor network system built in this way has timely and accurate data acquisition and can operate with extremely low power consumption.