Programmable wireless remote control technology single chip microcomputer system design

　　This paper introduces a design method of a programmable wireless remote control multi-channel switch system, and describes its composition structure and working principle in detail. This system uses a single chip microcomputer to perform software decoding on the received signal, avoiding the limitations of using a dedicated decoding chip, and can enhance the scalability and flexibility of the system. It has been proved to be a feasible solution through experiments.

　　1 Introduction

　　With the rapid development of integrated circuit technology, new remote controls based on various chips continue to emerge. The central control components of remote control devices have gradually developed from early discrete components and integrated circuits to current single-chip microcomputers, and the degree of intelligence has been greatly improved. In the field of wireless remote control, the commonly used remote control methods are mainly ultrasonic remote control, infrared remote control, radio remote control, etc. Due to the technical characteristics of radio waves, they can be realized in a large area and space, becoming the main method of remote control, and have a wide range of application value in production, construction and daily life. To this end, based on previous research, a design method for a programmable radio remote control multi-channel switch system based on single-chip microcomputer control technology was explored. Research shows that the remote control switch system designed by this method is easy to control, suitable for occasions with more controlled electrical appliances, and can realize multi-channel multi-function control.

　　2 System Design

　　2.1 System Analysis

　　The system structure mainly consists of antenna receiving part, signal transmitting part, single chip control part and driving part. Since radio signals are easily interfered by environmental factors, it is difficult to make it successfully without professional equipment. Wireless data transmission is different from wired data transmission. The transmitted data is only stable in a short time and will be interfered with after a long time. Therefore, encoding must be used to transmit the data. In the design, the high-frequency part uses a dedicated transmitting and receiving module, and the encoding and decoding of the data are also completed by hardware, which greatly improves the success rate of production; the control part is the core of the system. In order to enhance the scalability and flexibility of the system, make the circuit simple and clear, and save hardware design costs, mature single chip control technology is introduced into the system control link. The specific composition of the system is shown in Figure 1.

　　Figure 1 System structure diagram

　　2.2 Main circuits of the system

　　2.2.1 Transmitter system circuit

　　The transmitting system is mainly composed of a key addressing circuit, an encoding circuit, and a remote control transmitting circuit. The main component to complete the key addressing circuit is the priority encoder CD74HC147. CD74HC147 has nine input terminals and four output terminals. Both input and output are valid at low level, and the encoding has priority restrictions, that is, when there are more than or equal to 2 inputs, only the input with higher priority is valid; the main component to complete the encoding circuit is PT2262, which is a low-power, low-cost general encoding circuit based on CMOS technology. It has 12-bit three-state address terminal pins, and any combination can provide 531441 address codes. There can be up to 6 data terminal pins. The set address code and data code are serially output from pin 17 for wireless remote control transmitting circuit; the remote control transmitting circuit uses a 315MHz wireless transmitting module, which has 3 pins: the positive power supply pin, the ground pin, and the serial signal input pin. This module has a wide operating voltage range of 3V~12V, so when the voltage changes, the transmission frequency remains basically unchanged, and the receiving module matched with the transmitting module can receive stably without any adjustment. The characteristics of this module are relatively large transmission power and long transmission distance, which is suitable for communication under harsh conditions. [page]

　　The schematic diagram of the transmitting system circuit is shown in Figure 2.

　　Figure 2 Transmitter system circuit diagram

　　2.2.2 Receiving system circuit

　　The receiving system is mainly composed of receiving circuit, decoding circuit, single chip microcomputer circuit and switching circuit.

　　The main function of the receiving system is to first demodulate and decode the received signal, and then send the decoded data to the microcontroller, which controls the corresponding switch to operate according to the data.

　　The radio receiving circuit uses the RF receiving module J04E which matches the RF transmitting module F05C. J04E has a wide receiving bandwidth, extremely low power consumption, and can be in a long-term standby state. The output port of J04E is directly connected to the data input port of PT2272.

　　The decoding circuit uses the decoding chip PT2272 in the codec chipset PT2262/2272. The chip has address decoding, oscillation and system timing, data detection, synchronization detection, control logic, and decoding logic circuits. The A0~A7 terminals of PT2272 are the address code setting ports of the chip. Only when the address code of the receiving end and the address code of the transmitting end are exactly the same, the output end will have an output signal. The decoding chip PT2272 decodes and identifies the signal received at the data input end through the internal circuit. If the address code of the received signal is the same as the local address code, D0~D3 outputs the switch information corresponding to the radio transmission system to the single-chip microcomputer circuit, and the single-chip microcomputer controls the corresponding switch circuit action.

　　Otherwise, the decoding chip does not decode, the microcontroller circuit does not respond, and the switch circuit maintains its original working state unchanged.

　　The single-chip microcomputer circuit uses AT89C2051 to process the input signal and control the switch circuit. The P1.0~P1.3 terminals of AT89C2051 are used as data input ports, which are respectively connected to the data output D3~D0 terminals of the decoding chip PT2272. The signal output from the effective output terminal of PT2272 is used as the external interrupt trigger signal of the single-chip microcomputer. When the external interrupt samples the effective trigger signal, it interrupts the signal of the P1.0~P1.3 pins to control the state of the switch circuit. The P3.7 pin of AT89C2051 is connected to a buzzer to prompt the effective switch action.

　　The switch circuit is composed of 8550 transistors, 4007 diodes and relay groups. The relay in the switch circuit is a high-voltage circuit and cannot be driven directly by an integrated circuit chip. Therefore, a circuit to drive the relay must be set between the single-chip microcomputer and the relay. This system uses the cutoff and saturation states of the transistor to turn off or on the relay switch. Figure 3 only shows the switch control circuit schematic of the P1.7 port. The connection method of the I/O port not shown in Figure 3 and the P1.7 port is the same, so this design can remotely control 9 circuits.

　　The receiving system circuit is shown in Figure 3.

　　Figure 3 Schematic diagram of receiving system circuit

　　3 System Application

　　3.1 System control principle

　　The system mainly controls the state of the switch circuit by programming the single-chip microcomputer. By making full use of its software and hardware resources, it can control the various states of the controlled circuit, and can also control multiple circuits with a single key. Using the single-chip microcomputer control circuit to control the switch circuit also makes the control circuit easy to expand and flexible to control. The software decoding main program flow chart and interrupt control flow chart based on the single-chip microcomputer AT89C2051 are shown in Figure 4. [page]

　　Figure 4 MCU control flow and interrupt handling program flow chart

　　3.2 System Structure Analysis

　　The transmitting system addresses the switch of the controlled circuit through the encoder, and the receiving system controls the switch state of the controlled circuit through the single-chip microcomputer. The system expansion is relatively convenient and is suitable for occasions with more controlled electrical appliances. It can realize multi-channel multi-function control (for example, it can realize timing, delay and other operations). The radio frequency transmitting and receiving modules are adopted, which are easy to install and debug, with simple circuits, good reliability and high stability. The special encoding and decoding integrated circuits are adopted, and the repeated identification and confirmation inside the circuit improves the reliability of the system and avoids the problem of multiple radio remote control switch systems with the same structure interfering with each other within the effective distance.

　　4 Summary

　　In summary, the design of the multi-channel wireless remote control switch based on the single-chip microcomputer discussed in this paper uses a single-chip microcomputer to replace the traditional dedicated decoding chip PT 2272 to perform software decoding on the received signal, breaking through the strict requirements and paired use limitations of the traditional dedicated chip, and greatly expanding the scope of use of the chip. In addition, this method greatly enhances the scalability and flexibility of the system, makes the circuit simple and clear, and saves the cost of hardware design. The transmitting circuit adopts a special design to improve the transmission efficiency and reduce power consumption. This design is not only a good design idea, but also has very good use and promotion value.