A New Design of Programmable Wireless Remote Control Multi-way Switch

    Home lighting systems are closely related to people's lives. Most families still use ordinary switches, which can only control one set of lamps, and the service life of existing wireless remote control switches is relatively short, generally 2 to 3 years. It is very necessary to design a new wireless remote control switch that can control the lighting system and effectively increase the service life so that people can use it safely. This paper takes the wireless control of daily electric lights as the research object, and uses the Si1000 wireless transceiver chip developed by SILICon Laboratories to design a wireless remote control switch with high reliability, power saving and convenience. Si1000 integrates C8051f9xx low-power microcontroller and Si4432 RF module. Using this chip, a wireless light remote control switch with a frequency of 433.92 MHz is designed. It has a simple structure and stable performance to realize the function of multi-channel control of electric lights, and can also be applied to other applications.

    1 Working principle of wireless remote control switch

    The wireless remote control multi-way switch consists of a handheld remote control and a receiving control implementation unit. The system composition block diagram is shown in Figure 1.

    The working principle of the wireless remote control multi-way switch is as follows: first, the corresponding function key signal is input through the key circuit, and the internal single-chip microcomputer encodes the input key signal and adds the address code information, so as to form a coded pulse signal with address code information and corresponding light switch control status information, and then modulates it. The modulated signal is then amplified and tuned and then transmitted by the RF transmitting circuit; the radio receiving circuit receives the carrier modulation signal transmitted by the handheld remote control and demodulates it, and verifies and confirms its address code. If the remote control address code matches, the coded pulse signal is decoded to obtain data, and the single-chip microcomputer inside Si1000 controls the switch circuit, and the corresponding high and low level control circuit is output by the pin, thereby realizing wireless light control. Otherwise, no decoding is performed, and the single-chip microcomputer control circuit has no response.

    2 System Design

    2.1 Chip Introduction

    The Si1000 chip series launched by Silicon Labs integrates the ultra-low power C8051f9xx microcontroller and wireless RF module. When the processor performs data-related operations, it can provide very low operating current, thereby reducing power consumption. The low power consumption characteristics of Si1000 make its operating voltage 0.9-3.6 V, which can be powered by batteries. The Si1000 series of wireless microcontrollers integrates a 25 MHz 8051 core, an EZRadioPRO series RF transceiver device slightly lower than 1 GHz, a maximum of 64 kB Flash, and a maximum 12-bit resolution ADC. At the same time, the internal FLASH memory of Si1000 has reprogramming capabilities, which is convenient for users to further develop and use. The C2 interface is used for joint debugging of software and hardware, which is convenient and fast.

    2.2 Hardware Circuit Design

    As shown in Figure 2, it is the circuit schematic of the wireless remote control transmitter unit. The entire circuit is based on Si1000, and the wireless remote control can be divided into a power supply unit, a signal processing unit, a programming unit, and an antenna. The handheld remote control is powered by a battery. The main function of the wireless remote control transmitter unit is to collect the status information of the key circuit under the control of the internal MCU of Si1000, encode the status information, and at the same time, the internal module adds the corresponding preamble, synchronization word, data length and check bit according to the corresponding data packet format, and then performs FSK modulation. The modulated signal is amplified and tuned, and then transmitted by the transmitting antenna.

    
    As shown in Figure 3, the circuit schematic diagram of the wireless remote control receiving unit is shown. The wireless remote control receiving unit can be divided into a power supply unit, a wireless receiving unit, a signal processing unit, a programming unit, and a control implementation unit. The receiving single-channel power supply unit is composed of a transformer voltage regulator chip. The Si1000 supply voltage is 1.8 to 3.6 V. The wireless receiving unit uses a matching filter network to receive 433.92 MHz harmonics and sends the received signal to the microcontroller for processing; the signal processing and programming unit is processed by the Si1000 built-in microcontroller. The C8051f9xx low-power microcontroller integrated in the Si1000 demodulates the signal sent by the receiving unit through software settings, checks whether the address code information matches, and decodes it if it matches. The microcontroller processes the obtained information and sends a signal to the control unit through the port output, thereby finally realizing wireless control; otherwise, the circuit has no response.

    2.3 Software Design

    The system software adopts modular design, and the functional modules mainly include: chip parameter initialization module, wireless transmission module, wireless reception module, etc. The system adopts C2 interface programming, and the C2DATA, C2CLK port, V CC and GND of Si1000 are connected to the 4 ports of JTAG interface.

    The communication between wireless transceiver modules is carried out in the form of data packets. The data packet format used by this wireless remote control system is shown in Table 1. A data packet consists of a preamble, a synchronization word, a data length, data, and a check bit. The preamble is used to synchronize the transmitting and receiving units well, that is, to find the starting position of a frame of data. It consists of several groups of 10101010, with a total of 8n bits, and the size of n is determined by user programming; the synchronization word is for better synchronization in order to find the frame header, and the flag code of the synchronization mode is the set synchronization word. The data carries the key information, that is, the encoding of each key . Finally, the check bit is used to check the frame data to detect the correctness of the data. In practical applications, it can be selected according to the actual situation. The wireless transmission module uses such a data packet to send the data out.

    Si1000 contains C8051FXX and RF module, so it can complete signal modulation, signal demodulation, data encoding and data decoding, etc. The hardware automatically adds preamble, synchronization word, data length and data check bit. After power-on, the program completes the parameter initialization of Si1000 and the initialization of SPI interface and RF, and writes the corresponding initialization RF control word into the configuration register. After the system initialization and parameter configuration are completed, the level of pin nIRQ is detected. If it is low, it means that the system has changed to receiving mode and has detected the data packet. The data packet length information is read through register 4BH, and the "valid packet interrupt" and "data packet interrupt" are turned on. Other interrupts are prohibited, and the system receives and processes data.

    The radio control system sets the synchronous mode flag code to 0x2DD4. Once the receiving module detects this synchronous word, it will receive data synchronously. Wait for the interrupt to be generated, the nIRQ pin becomes low level, receive the data packet, and read the interrupt flag to reset the nIRQ pin, so that the nIRQ pin becomes high level to prepare for the next interrupt trigger detection; through the received data, first confirm the address information, if it matches, decode it, judge the light control state from the code word, and then the built-in microcontroller of Si1000 performs corresponding processing and outputs the corresponding control signal, so as to realize the control function, otherwise the circuit will not respond.

    3 Conclusion

    According to the existing problems and design requirements, this paper uses the Si1000 integrated chip to design a wireless communication control system with the advantages of convenience, speed, low power consumption and long service life. It also conducts software and hardware debugging and proves the feasibility of the design under limited conditions. At the same time, this paper only takes daily lighting control as an example, but this series of chips can be further promoted and applied in industrial production, access control systems, smart homes and other aspects in the future.