Design of short-range wireless data transmission system based on microprocessor and RF transceiver chip
This paper introduces a specific method for designing short-range wireless data transmission system using high-performance, low-power 32-bit microprocessor STM32F103 and RF transceiver chip nRF24L01.
1 System Design The short-range wireless data transmission system is mainly composed of power manager AMC7635, microcontroller STM32F103, and RF transceiver nrf24l01. The key circuits are described below.
1.1 Power Circuit The power supply of this design is powered by a 3.7V lithium battery, and then passed through the low-voltage drop power management chip AMC7635 to generate a voltage of 3.0V to supply power to the STM32F103 and nRF24L01. Figure 1 shows the power supply circuit of the system.
Figure 1 System Power Supply Circuit 1.2 Microcontroller Circuit The microcontroller uses the STM32F103 with ARM Cortex -M3 core. The STM32F103 controller features high performance, low power consumption, low voltage, and high integration and ease of development. Figure 2 shows the microcontroller circuit in the system. The interface between the controller and the RF transceiver nRF24L01 is realized by the SPI port, namely, the four signal lines SPICS, MOSI, MISO and SCK in Figure 2 and the two signal lines CE and INT0. In addition, the controller can also extend the output of one motherboard RS232 port and eight GPIO ports.
Figure 2 Microcontroller circuit
1.3 RF Transceiver Circuit The nRF24L01 can operate in the 2.4 GHz to 2.5 GHz ISM band. The transceiver is equipped with a frequency synthesizer, power amplifier, crystal oscillator, modulator and other functional modules. It is a highly integrated wireless transceiver. The external circuit of the nRF24L01 is relatively simple and incorporates the enhanced ShockBurst technology, where the output power and communication channel can be configured through the program. At the same time, the chip's power consumption is extremely low. When transmitting at -6 dBm, its operating current is only 9 mA. At the time of reception, the operating current is only 12.3 mA. The control circuit of the nRF24L01 can be connected to the SPI port and GPIO port of the STM32 controller. Figure 3 shows the schematic diagram of the RF transceiver circuit composed of the chip.
Figure 3 RF transceiver circuit 2 System programming This system can transplant UCOSII operating system on STM32F103. The system program is mainly divided into three parts: the system initialization program of the host, the keyboard and display program, and the control program of the RF transceiver nRF24L01. Figure 4 shows the software program flow.
Figure 4 System program flow chart The key to system programming is the migration of UCOSII operating system and SPI port communication control. Regarding the porting of the operating system, the chip manufacturers have provided examples on the official website, and will not be repeated here.
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