Design of positioning card: STM32 is the main control core of the positioning module. St (Italian French semiconductor) stm32wcbu6x chip is used in the positioning module, which adopts 32-bit armcortex-m3 core; Stm32wcbu6x integrates a 2.4GHz ieee18.104.22.168 compatible transceiver with 128KB flash and 8KB ram. It is a high-performance wireless system on chip (SOC). The schematic diagram of the main control is shown in Figure 3.
Fig. 3 Schematic diagram of main controller
Circuit analysis:The system needs an external MCU to control the data sending and receiving of the module, so the external MCU needs to communicate with the module, and its connection mode is (USART) serial port. The module provides a standard compliant USART interface, whose IO level is limited to 2.4 ~ 3.6V, and the nominal logic level is 3.3V. The module serial port connects its TX end to the RX end of the external MCU without using hardware flow control; The RX end of the module is connected to the TX end of the external MCU.
Summary:In the design of the positioning system, the ZigBee module of the hardware part adopts STM32 as the main controller, which improves the work efficiency of the whole system and provides great help to the accuracy of personnel positioning. The ZigBee equipment in this scheme can be powered by ordinary batteries, and one battery can be used for at least 6 months, reducing the cost to a certain extent. For the relationship between communication distance and signal strength, the maximum likelihood estimation method is used to reduce the error.