Design of data transmission interface circuit of automobile drive recorder

Car Audio Crystal 3.2*2.5mm 3225 24M (24.000MHZ) 20PF 10PPM 20PPM 30PPM

The outer diameter of the probe domestically produced P02-T chisel head nickel-plated needle is 0.68mm. The total length of the needle is 24

USB data transmission interface circuit design

The USB interface has the characteristics of fast data transmission, simple connection and good compatibility. The national standard for vehicle tachographs takes into account the popularity of the RS232 interface and the advancement of the USB interface, and stipulates that both interfaces are used for data communication. The PDIUSBD12 chip is used as a USB controller in the USB data transmission design. The PDIUSBD12 is fully compliant with the USB 1.1 specification; it also conforms to the classification specifications of most devices; it is also suitable for many peripherals such as printers, scanners, external storage devices and digital cameras, which makes current SCSI systems available. Reduce costs immediately.

The single-chip microcomputer directly reads and writes the flash disk, and can realize the plug-in mass storage of the portable device or the embedded system. The core of this technology is the USB-HOST technology, the implementation of the FAT file system specification, the implementation of the mass storage protocol and the implementation of the USB bulk transfer method. The protocols involved are numerous and the technical difficulty is very high. In the design shown in Figure 3, the USB interface chip uses Cypress's USB-HOST interface chip SL811, which supports the USB 1.1 protocol, low price, outstanding performance and high reliability. The file system is in FAT format and is compatible with Windows 98 and Windows 2000/XP. For most manufacturers, the flash drive can be successfully accessed.

In order to improve the reliability and EMI characteristics of the circuit, the following rules should be paid attention to in the process of circuit board design and wiring: add decoupling capacitor between power supply and ground line; try to widen the power supply and ground line width, preferably ground The line is wider than the power line; the signal line is placed on the electrical (ground) layer; in a large area of ​​ground (electric), the pins of the common components are connected to it, and the processing of the pins needs to be comprehensively considered; the wiring design is completed. After that, it is necessary to check whether the wiring design meets the rules set by the designer, and also to confirm whether the established rules meet the requirements of the printed board production process.