Design of USB video data acquisition system interface circuit

　　Nowadays, sockets and ports have many functions, and the interfaces or applications will be different depending on the usage. Some have added insurance functions, power indication functions, 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 power interfaces 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 sockets, we will combine the intelligent information system designed by research 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 powered by lighting power, people use it just like using an ordinary power socket, eliminating the need for excessive connecting wires.

　　USB interface chip and its working principle

　　In this article, we use the PDIUSBD12 chip, 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 operation. (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) With programmable clock output, 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.