Radio frequency chip RF401 and a highly reliable remote control circuit composed of it

RF401 is the latest 433MHz single-chip wireless transceiver integrated chip in the data transmission frequency band launched by Norwegian Nordic Company. The chip integrates high-frequency transmission, high-frequency reception, PLL synthesis, FSK modulation, FSK demodulation, multi-channel switching and other functions, and has excellent performance. , low power consumption, easy to use and other characteristics, nRF401 has very few peripheral components, including only a reference crystal oscillator and several passive components, and no debugging components, which brings great convenience to development and production. Table 1 is the electrical performance parameters of NRF401. Paremeters Value Unit Working channel 433.92/434.33 MHz Modulation method FSK Frequency offset 15 KHz Frequency offset output power 0.4k, 3v 10 dBm Receiving sensitivity 0.4k, BR=20 kbit/s BER<10 -105 dBm Maximum transmission bit rate 20 K bit/s Applicable voltage range 2.7" 5.25 V Receiving state power consumption 250 uA Transmitting state power consumption -10 dBM 8 mA Waiting state power consumption 8 8uA Table 2 is the NRF401 pin function table Pin Name Pin function Description 1 XC1 input reference oscillator input terminal 2 VDD power supply port (+3-5V DC) 3 VSS ground (0V) 4 FILT1 input filter access port 5 VCO1 input voltage-controlled oscillation inductor port 6 VCO2 input voltage-controlled oscillation inductor Port 7 VSS Ground (0V) 8 VDD Power supply port (+3-5V DC) 9 DIN input transmit data input 10 DOUT output receive data output 11 RF_PWR input RF power setting 12 CS input channel selection CS="0"=> 433.92MHz(Channel#1) CS="1"=>434.33MHz(Channel#2) 13 VDD Power supply port (+3-5V DC) 14 VSS Ground (0V) 15 ANT2 input/output antenna interface 16 ANT1 input /Output antenna interface 17 VSS ground (0V) 18 PWR_UP Input power on/off PWR_UP="1" =>Power up (Operating mode) PWR_UP="0" =>Power down (Standby mode) 19 TXEN Input operating mode TXEN = "1" => Transmit mode TXEN = "0" => Receive mode 20 XC2 output reference oscillator output terminal Figure 1 is a typical application circuit of RF401. In the figure, the antenna port ANT1 ANT2 outputs to a 600 Ω printed antenna, C10 C11 is the common vibration capacitor of the antenna loop, and the function of R4 is to appropriately reduce the Q value of the antenna loop. The maximum transmit power of this circuit is 10dBm, and the receiving sensitivity is as high as -105dBm. The maximum distance of use in open areas can be up to 1000 meters. For a large usage distance, a 600-50 balanced unbalanced conversion circuit can be added to the ANT1 ANT2 output port and connected 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 . Circuit. The microcontroller IC2.PIC16C57 is used to control the transceiver status of NRF401. At the same time, the microcontroller also completes encoding and decoding tasks at the same time. In the sending state, IC2 receives the low-level signal when the button is pressed, and sends a high-level signal from the pin to make NRF401 enter the transmitting state. At the same time, different crystals are randomly selected and with the cooperation of CS, the transmitting frequency is between 4.44 and 6. Jump between times. At each frequency point, DIN transmits the same data information of the two frequencies. After burning, it jumps to the next frequency point. The transmission timing is as shown below. When no button is pressed, it is in the receiving state. At this time, the IC2 pin sends a low level. Put NRF401 into the receiving state. At the same time, select each crystal in order and with the cooperation of CS, make the receiving frequency change sequentially from low to high at 4.44. The working time of each receiving frequency point is 7 times the working time of the transmitting frequency point. .To ensure that a complete transmission information can be received within the working time of each receiving frequency point. The receiving working sequence is as shown below. The received information is processed and decoded by IC2 and then sent out from the corresponding key port. Due to each receiving status The working time of the frequency point is 7 times that of the transmitter. Therefore, when several transmitters with different frequency hopping patterns work at the same time, the receiver can receive the information of each transmitter in time and make corresponding output. In a remote control with multiple remote controls The system ensures that when two or more remote controls are used at the same time, the control information of each remote control can be executed. It overcomes the problem that two remote controls cannot be used at the same time in a remote control system with a single working frequency. Simultaneous multi-frequency point working mode It also greatly enhances the anti-interference ability of the system. In remote control systems that require very high reliability, the remote control can understand whether the operation has been executed through the information sent back by the receiver. The EEPROM in the circuit is used to store the sequence of transmitting frequency jumps and Encoded data.