[Photos] RF chip 401 and high-reliability remote control circuit constructed with it

Radio frequency chip 401 and high-reliability remote control circuit formed by using the same

RF401 is the latest single-chip wireless transceiver chip with a digital transmission frequency band of 433MHz launched by Nordic Company of Norway. The chip integrates high-frequency transmission, high-frequency reception, PLL synthesis, FSK modulation, FSK demodulation, multi-channel switching and other functions. It has the characteristics of excellent performance, low power consumption and easy use. The peripheral components of nRF401 are very few, including only a reference crystal oscillator and several passive components, and no debugging components, which brings great convenience to the development and production.
Table 1 is the electrical performance parameters of NRF401

Table 2 is the NRF401 pin function table

Figure 1 is a typical application circuit of RF401. In the figure, the antenna ports ANT1 and ANT2 are output to a 600 printed antenna. C10 and C11 are the resonant capacitors of the antenna loop. The function of R4 is to appropriately reduce the Q value of the antenna loop. The maximum transmission power of this circuit is 10dBm, and the receiving sensitivity is as high as -105dBm. The maximum operating distance in open areas can reach 1000 meters. If you need to increase the operating distance, you can add a 600-50 balanced-unbalanced conversion circuit to the ANT1 ANT2 output port and connect it to the input and output amplification and conversion circuit.

Figure 2 is a high-reliability wireless remote control circuit composed of NRF401.

This circuit is both a transmitting circuit and a receiving circuit. The single-chip microcomputer IC2.PIC16C57 is used to control the receiving and transmitting state of NRF401. At the same time, the single-chip microcomputer also completes the encoding and decoding work. In the transmitting state, IC2 receives the low-level signal of the key being pressed, and sends a high level from the foot to make NRF401 enter the transmitting state. At the same time, different crystals are randomly selected and the transmitting frequency jumps between 4.44..6 with the cooperation of CS. At each frequency point DIN, the same data information of two frequencies is transmitted. After burning, it jumps to the next frequency point. The transmission timing is as shown in the figure below.

When no key is pressed, it is in receiving state. At this time, IC2 pin sends a low level to make NRF401 enter receiving state. At the same time, each crystal is selected in sequence and the receiving frequency changes from low to high in 4.44... with the cooperation of CS. The working time of each receiving frequency is 7 times that of the transmitting frequency. To ensure that a complete transmission information can be received within the working time of each receiving frequency. The receiving working sequence is as shown in the figure below.
The received information is processed and decoded by IC2 and sent from the corresponding key port. Since the working time of each frequency point in the receiving state is 7 times that of the transmitting, when several transmitting frequency hopping patterns with different transmissions work at the same time, the receiving can receive each transmitted information in time-sharing and make corresponding outputs. In a remote control system with multiple remote controllers, it is guaranteed that when more than two remote controllers are used at the same time, the control information of each remote controller can be executed. It overcomes the problem that two remote controllers cannot be used at the same time in a remote control system with a single working frequency. At the same time, the multi-frequency working mode also greatly enhances the anti-interference ability of the system. In a remote control system requiring very high reliability, the remote control can understand whether the operation is executed through the information sent back by the receiver.
The EEPROM in the circuit is used to store the sequence and coding data of the transmitting frequency jump.