Design of Wireless Meter Reading Terminal Circuit Based on MSP43O and Zigbee

This paper introduces a wireless meter reading terminal based on Zigbee network with MSP430F149 as the core. Specifically elaborated the terminal's main features, hardware circuit design and software design. The test results show that the design has the characteristics of stable operation and high reliability. It can be widely used in wireless centralized meter reading of various types of water, electricity, and gas meters, and has a good application prospect.

Circuit principle: The core processor uses TI's MSP430F149 microcontroller. In order to realize the requirement of low power consumption, two high-speed and low-speed crystal oscillators are used in the circuit, and a high-frequency crystal oscillator generates a high-frequency MCL-K to meet the requirements of high-speed data calculation of the CPU. When the CPU is not required to work, the high-speed crystal oscillator is turned off. The low-speed crystal generates the lower frequency ACLK and runs the real-time clock. The calendar clock chip uses PCF8563 from PHILIPS. This chip supports IIC bus interface, uses low-power CMOS technology, has a wide operating voltage range of 1.0V ~ 5.5V, under the 3.0V power supply conditions, the operating current and sleep current are typically 0.25μA ,Can record century, year, month, day, week, hour, minute, second, with timing, alarm and frequency output function. The memory uses FM24C04 from Fudan Microelectronics. This chip is a two-wire serial EEPROM, compatible with IIC bus interface, using low-power CMOS technology, with a wide operating voltage range of 2.2V ~ 5. SV, under the 3.0V power supply condition, the rated current is 1mA, and the sleep current is 5μA typical. In the case of power-down, the data in the memory can be stored for 100 years.

MSP430F149 has two serial interfaces with TTL level in hardware, one way is converted into RS485 serial interface through SP3485 chip and communicates with the digital power meter connected on the bottom, and the other way communicates with CC2430 directly. The RS485 bus is supported by most of the current digital energy meters. It uses balanced transmission and differential reception to achieve communication. It has strong resistance to common-mode interference, can transmit signals up to 1000 meters, and supports multi-point data communication. The CC2430 chip that complies with the Zigbee protocol supports a TTL-level serial interface, so it is possible to communicate with the core processor without interface conversion.

In the design process of this terminal, the selection of all devices takes into consideration the low power consumption requirements. Even if the battery is used, each battery replacement can be used for at least two years. And the selected components all support 3.3V voltage. All circuits need only a single power supply for stable operation. Figure 1 is the hardware schematic of the terminal, omitting the power supply voltage regulator circuit, filter circuit and some external components. The LED1, LED2, and LED3 in the figure are used to indicate reception data, transmission data, and wireless network status, respectively.

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