In instrumentation and measurement and control technology, wireless data communication is widely concerned for its advantages of saving transmission line and convenient use. The medium and short distance (less than 500 meters) wireless communication has a wide market in the practical application of automatic test system, wireless meter reading, computer telemetry and remote control system, vehicle monitoring system and community management. Among many wireless transceiver chips, nRF401 is popular because of its low cost, high reliability and simple peripheral design. However, due to the complexity of communication space, the wireless communication system is easy to receive error code. Even if the sender does not send data, the receiver will still receive a lot of interference data. In a medium-sized system design, the CPU has to carry out a variety of operations, such as external memory access, sensor data processing, etc., so when there are many wireless communication interference information, especially in the interrupt communication mode, frequent interrupts will seriously affect the operation of the main program, It is also necessary to switch the receiving and sending status and operation mode of nRF401. Therefore, for a system with bus structure (such as 485 communication mode), when the wireless communication part is also used as an independent ID module, the traditional design and processing encounter difficulties. Therefore, it is necessary to set an intermediate processing link, which can effectively filter information without affecting the communication speed.
In order to solve the above problems, this design based on nRF401 as wireless transceiver chip, using two AT89C2051 as control chip, designed a set of wireless communication system. One AT89C2051 (defined as control chip a) controls nRF401. The IO interface of AT89C2051 and serial port cooperate to control nRF401 to realize asynchronous communication; Another chip AT89C2051 (defined as control chip b) can not only meet the requirements of the bus serial port, but also solve the problem that control chip a can not respond to the bus in time due to frequent serial interruption. It plays the role of sharing tasks, isolating interference and expanding the serial port. Compared with the design of a single chip microcomputer with double serial ports, the design method of two 2051 single chips can reduce the cost, improve the utilization rate of the chip and isolate the interference. Practice shows that the system has simple structure, strong anti-interference ability, and can solve the problem of wireless communication between short distance systems.
Design of wireless communication module based on nRF401
NRF401 is a single chip UHF wireless transceiver developed by Nordic company, which works in 433MHz ISM band. In the receiving mode, nRF401 is configured as a traditional heterodyne receiver. The received RF modulated digital signal is amplified by a low noise amplifier, converted into if by a mixer, amplified and filtered before entering the demodulator. After demodulation, it is converted into digital signal output (dout end). In the transmitting mode, the digital signal is input through the din terminal, processed by the PLL and VCO, and then sent to the RF output of the power amplifier. In the design of this system, in order to avoid interference, the wireless transceiver based on nRF401 is made on a separate PCB board, which leads out the communication control interface (J1) to form an independent wireless transceiver module.