Design of USB interface communication circuit for multifunctional intelligent socket

　Existing sockets have shown a trend of diversification in terms of their usage, functions, and appearance features. Some have added insurance functions, power indication functions, and switch functions, and some have added voltage regulation functions. No matter what the functions of these sockets are, they can only have a single purpose: to provide a power interface for electrical equipment. Their common defect is that they do not have information and intelligent functions. In order to realize the informatization and intelligence of the socket, we will combine the intelligent information system we have studied and designed with the socket, integrate the intelligent device with the power socket, and design it into a multifunctional intelligent monitoring socket. Since the socket is fixed once during the electrical installation of the building and is powered by lighting power, people use it just like using an ordinary power socket, eliminating the need for excessive connecting wires.

　　Interface chip and its working principle

　　In this article, we use the PDIUSBD12 chip launched by Philips, which is a cheap and fully functional parallel interface chip that supports multiplexing, non-multiplexing and DMA parallel transmission. The PDIUSBD12 interface chip complies with the USB1.1 protocol and is suitable for transmission types for different purposes. PDIUSBD12 requires an external microcontroller (MCU) for protocol processing and data exchange. It has no special requirements for the MCU, and the interface is convenient and flexible. Therefore, designers can choose the MCU they are familiar with to control the chip, or use Philips' firmware structure to shorten development time, reduce risks, and reduce investment.

　　Performance characteristics: In addition to the general characteristics of USB devices, PDIUSBD12 also has the following characteristics: (1) It is a high-performance USB interface chip that integrates SIE (Serial Interface Engine), 320-byte FIFO, transceiver and voltage regulator. (2) It is applicable to most device class specifications. It can realize high-speed parallel interface with any external microcontroller/microprocessor, and its speed can be as high as 2Mbit/s. (3) It can perform completely independent DMA operations. (4) The master endpoint is configured with double buffering, which can improve data throughput, reduce data transmission time, and easily realize real-time data transmission. (5) When using synchronous transmission mode, the data transmission speed is 1Mbit/s; while the speed of bulk transmission mode is 1Mbyte/s. When using the above methods for data transmission, multiple interrupt modes can be conveniently used. (6) It has a programmable clock output, and the connection with the USB bus can be controlled by software (Soft Connect TM). (7) There are two operating voltages to choose from: 3.3±0.3V and 3.6~5.5V. (8) Output and data transfer status can be monitored via the USB connection indicator.

　　Communication hardware circuit design

　　In this paper, we choose 89C52 single-chip microcomputer as the microcontroller of the system. The circuit connection between PDIUSBD12 and 89C52 is shown in Figure 1:

　　Figure 1 USB interface communication circuit

　　Converter card circuit design

　　The design includes the MCU software (firmware) design and the host software design. The MCU software is developed using the WAVE simulation software provided by Weifu Company and debugged online through its simulator. The host software includes two parts: the driver and the application, which are generated using DDK and VC6.0 respectively.

　　Figure 3 USB interface conversion card circuit diagram

　　The research on the intelligent monitoring socket is still in the theoretical conception and design process. There is still a long way to go to make a product, and more people need to invest more energy. Especially in the use of USB communication, the writing of USB driver is a difficult point. With the continuous updating, improvement and development of technology, I believe that the realization of the multi-functional socket will become easier and easier.