Design of Programmable Radio Remote Control Multi-way Switch System

Compared with wired remote control, wireless remote control is not affected by distance, completely eliminating the hidden trouble caused by the towing cable remote control device, and bringing more convenience to people's daily work and life. With the rapid development of digital processing technology, wireless digital communication technology is becoming more and more mature. Its advantages such as strong anti-interference ability and easy processing of digital signals have gradually improved the anti-interference performance of wireless remote control systems and greatly improved safety performance. At present, the main fields of wireless remote control include ultrasonic remote control, infrared remote control and radio remote control. Compared with ultrasonic remote control and infrared remote control, radio remote control uses radio signals to propagate in the air and controls remotely according to the frequency of radio waves. It can penetrate certain obstacles and has a long transmission distance. Therefore, it has become the first choice in the field of wireless remote control and is increasingly used in the fields of national defense, military, scientific research and daily work and life.

The wireless remote control multi-way switch system with a frequency of 433.92 MHz is designed and manufactured using the wireless transmitter chip Si4010, wireless receiver chip Si4313 and C8051F920 microcontroller developed by Silicon Laboratories. It has a simple structure, stable performance, and convenient control. It is suitable for occasions with a large number of controlled electrical appliances and can realize multi-channel and multi-functional control.

1 System Working Principle

The wireless remote control multi-way switch system consists of two parts: the radio transmitter circuit and the radio receiver control circuit. The system composition block diagram is shown in Figure 1.

Figure 1 System composition block diagram

The working principle of the switch system is to first input the bit number of the required control switch circuit through the key circuit, and at the same time start the command encoding circuit. The command encoding circuit generates a coded pulse signal with address coding information and switch status information under the control of the internal circuit. The pulse signal modulates the carrier signal. The modulated carrier signal is amplified and tuned and transmitted by the RF transmitting circuit. After the radio receiving circuit receives the carrier modulation signal, the demodulation and decoding circuit demodulates the carrier modulation signal to obtain a coded pulse signal, and then confirms the coded address to confirm whether it is the address of this remote control switch system. If the received signal address code is the same as the local address code, the coded pulse signal is decoded and output, and the corresponding switch circuit action is controlled by the single-chip microcomputer circuit. Otherwise, no decoding is performed, the single-chip microcomputer control circuit does not respond, and the switch circuit has no action.

2 Hardware Introduction 2.1 Introduction to Si4010 Silicon Laboratories' Si4010 RF transmitter is a single-chip remote control IC that only requires an external bypass capacitor, a printed circuit board, a battery, and a housing with buttons to form a complete radio remote control. The patented high-reliability crystal-free oscillator architecture does not require an external clock source and is not affected by shock and vibration. Its carrier frequency accuracy is ±150 ppm in the commercial temperature range and ±250 ppm in the industrial temperature range. Its accuracy is twice that of traditional (SAW) transmitters and no external crystal oscillator is required. It has automatic antenna tuning, which can maximize the transmission distance, provide stable output power, and effectively reduce adverse effects on the remote control. It contains an embedded 8051-compatible microcontroller with 1 4 kB RAM, 1 8 kB one-time programming (OTP) non-volatile memory, 1 128-bit EEPROM and 12 kB ROM for library functions. The digital peripheral functions on the microcontroller include touch wake-up GPIO, 1 patented 20-bit EEPROM with a read-write life of 1 million times, 1 LED driver, 1 sleep timer, 1 debugger, and 1 high-speed 128-bit Advanced Encryption Standard (AES) accelerator that can provide a secure unidirectional link. The operating voltage range of Si4010 is 1.8 to 3.6 V, providing ultra-low current consumption (less than 10nA standby current and less than 20 mA peak current) and low-power touch wake-up mode. It supports FSK and OOK modulation modes, supports PCB loop antennas, and has an operating frequency band of 27 to 960 MHz. The chip also contains LDO, temperature sensor, and low voltage detection alarm. 2.2 Introduction to Si4313 Silicon Laboratories' Si4313 chip is a single-ended general-purpose ISM band receiver with an operating frequency of 240 to 960 MHz, a programmable receiving frequency bandwidth of 2.6 to 260 kHz, a receiving sensitivity of -118 dBm, a data rate of 0.2 to 128 kb/s, and uses FSK, GFSK, and OOK modulation schemes. It supports frequency modulation, single capacitor tuning network, and PCB loop antennas. The operating power supply voltage is 1.8 to 3.6 V, and it has ultra-low power consumption, high flexibility, and low shutdown mode. Internal functions include: wake-up timer, automatic frequency calibration, front-end code detection, radio signal strength detection, integrated voltage regulator, on-chip oscillator, 64 kB FIFO, etc. 3 System Hardware Circuit Design 3.1 Radio Transmitter System The radio transmitter system is mainly composed of key circuit, coding modulation circuit and radio transmitter circuit. The circuit schematic diagram of the radio transmitter system is shown in Figure 2.

Figure 2 Schematic diagram of the transmitting system circuit

The radio transmitting system is designed with Si4010 as the core. The four input and output ports of Si4010 are directly connected to the buttons, and the internal circuit can directly collect the button status information. The signal differential output terminals TXM and TXP of Si4010 are respectively connected to the two ends of the loop antenna. The loop antenna is directly printed on the PCB board, which reduces the size of the transmitting system. Using C2 interface programming, the C2DATA and C2CLK ports of Si4010 are connected to the four ports of the JTAG interface. C3, C4, and C5 form a power filter circuit. The light-emitting diode provides a button action indication. When a button is pressed, the light-emitting diode is on, and when no button is pressed, the light-emitting diode is off. The main function of the radio transmitting system is to collect the status information of the button circuit under the control of the internal MCU of Si4010, realize data encryption and encoding, and then perform FSK modulation. The modulated signal is amplified and tuned and transmitted by the loop antenna.

3.2 Radio receiving system The radio receiving system is mainly composed of radio receiving circuit, demodulation and decoding, single chip control circuit and switch circuit. The circuit principle of the radio receiving system is shown in Figure 3.

Figure 3 Schematic diagram of receiving system circuit

The receiving demodulation circuit is implemented by the wireless receiving chip Si4313 that matches the RF transmitter module. The control unit uses the C8051F920 microcontroller.

The RX port of Si4313 is connected to the antenna through capacitor C1 to receive the remote control modulated carrier signal. The communication between Si4313 and the microcontroller is realized through the SPI bus. The SPI bus read and write operation consists of the following parts: read and write flag (1 bit), address (7 bits) and data (8 bits). The read and write flag indicates whether the current operation is read or write; the 7-bit address indicates the operation object, which can address any one of the 128 8-bit control registers; the data field contains the contents of the Si4313 internal register written or read. The SCLK, SDI, SDO, nSEL, and nIRQ ports of Si4313 are connected to the P0.0~P0.4 ports of the microcontroller respectively. SCLK is the clock interface; SDI is the serial data write port, and the microcontroller writes data to Si4313; SDO is the serial data output port, and the demodulated digital signal is output to the microcontroller from this port. The microcontroller P1.0~P1.3 is the control port, which is connected to the switch circuit.

The main function of the radio receiving system is to receive the remote control carrier modulation signal, demodulate and decode the modulation signal through the demodulation and decoding circuit, and output it serially to the microcontroller, which processes the data and then controls the corresponding switch action of the switch circuit through the control port.

4 System Software Introduction

The software programming adopts modular design concept. Each main functional module in the system is compiled into an independent application function and called by the main program.

4.1 Transmitter System Software

The software design of the radio transmitter system mainly realizes the control of the state of the wireless transmitter circuit by the 8051MCU integrated in Si4010 through C2 interface programming. It includes chip initialization program, keyboard scanning and reading program, RF parameter setting program, wireless transmission program, etc. The transmitter system software flow is shown in Figure 4.

Figure 4 Transmitter system software flow chart

4.2 Receiving system software The software of the radio receiving control system is designed based on the C8051F920 single-chip microcomputer, and the single-chip microcomputer controls the state of the switch circuit through C2 programming. When the single-chip microcomputer samples a valid interrupt request signal, it executes the interrupt service subroutine. In the interrupt service subroutine, the single-chip microcomputer will execute the corresponding subroutine according to the data obtained from the I/O port, thereby realizing the control of the switch circuit. The receiving system software flow is shown in Figure 5.

Figure 5 Receiving system software flow chart

5 Conclusion This paper uses low-cost, ultra-low power single-chip wireless remote control IC and single-chip microcomputer to design a programmable radio remote control multi-way switch system, which has the characteristics of low cost, small size, low power consumption, strong anti-interference ability, long remote control distance, and high reliability. After comprehensive testing of software and hardware in the laboratory, the receiving demodulation circuit receives and demodulates the remote control signal of the transmitting circuit normally, the switch circuit operates in place, and the multi-channel multi-function control of the radio remote control switch system is normal. It can be further promoted and applied, and has broad application prospects in industrial production, security monitoring, smart home and other fields.