3G car video transmission system design

At present, the requirements of data transmission in the field of vehicle monitoring are getting higher and higher. This paper starts with the hardware and software design of the system and introduces the 3G car video transmission module. The hardware part focuses on the design of video capture and 3G transmission. The software part introduces the driver design of the U6100 module, 3G network access program design and video transmission program design. Finally, the analysis of the RTP data packet and the observation of the client video prove that the design has achieved good results.

The vehicle 3G high-definition video transmission system uses dynamic image acquisition technology, automatic control technology, image processing technology, computer communication technology and other high-tech to establish a mobile video information forensics platform with the vehicle host as the core, and provides traffic law enforcement personnel with vehicle violation driving HD capture. , mobile video dynamic forensics, traffic scene command and other information services.

Due to the continuous development of 3G wireless network technology and embedded technology, the rapid development of video surveillance has been promoted, especially in the field of automotive monitoring. The 3G wireless network covers a wide area and can be flexibly accessed. Compared with the previous wireless video communication technologies such as GPRS and CDMA, the transmission speed is much faster, but the practical application of 3G technology in the field of automobile monitoring is not perfect. DM365 supports H.264 video coding technology to ensure high-quality transmission of video data under limited network bandwidth. The U6100 module can be integrated into any 3G mobile device and can be connected to high-speed networks such as HSDPA, HSUPA, and UMTS. Therefore, we designed a car video transmission module with TI's DM365 as the core and U6100 as the transmission module.

1 3G car video transmission module hardware design

The video transmission module designed in this paper is applied in the vehicle monitoring equipment, so when we carry out the design of the scheme and the choice of hardware, the transmission requirements of the video are the first to bear the brunt. In view of the good compatibility between the software and hardware of the DM36X series, the Davinci platform facilitates the algorithm expansion, so the TMS320DM365 chip is used to build the 3G vehicle video transmission system.

The hardware platform of this module is mainly composed of the following parts: video capture and processing part, local storage and display part, 3G video transmission part, power part. The hardware frame diagram of the video transmission module of the vehicle terminal is shown in Figure 1.

Figure 1: Hardware structure of the video transmission module of the vehicle terminal

1.1 Video Capture and Processing Section

The video capture part consists of a PAI/NTSC pan/tilt camera and a video codec chip TVP5151. The PTZ camera needs to be controlled by RS485. Since there are only two serial interfaces (UART) on the DM365, they are already occupied (one for connecting serial port debugging and one for connecting GPS module). Therefore, we use the USB port of the USB HUB to perform a two-level conversion. First, we use LP2303 to convert to 232, and use MAX485 to convert to 485 for PTZ control.

The TVP5151 and processor are docked with an I2C bus that converts the incoming analog signal into a digital signal.

The video processing part uses TI's DM365 HD video processor. DM365 supports H.264 video coding technology, which guarantees high-quality video data transmission under the condition of 3G wireless network transmission.

1.2 Local storage and display section

The DM365 provides a dedicated external memory interface that includes a Flash interface and an SDRAM interface that can be connected to external memory. In the design of this vehicle terminal, we chose Samsung's 1GB capacity, 8-bit data line K9F 8G08UOB NAND Flash chip and 128MB capacity, 16-bit data line K4T1G164QE DDR SDRAM chip.

In order to make the operation of the vehicle terminal more user-friendly, we chose a 5.7-inch TFT-LCD touch screen panel from Taiwan Jingcai Optoelectronics Co., Ltd. for the display part. The panel has a high resolution of 640X480. It supports I2C bus or SPI bus. Considering the actual situation of the upper layer driver, the I2C bus is used to connect with the main chip.

1.3 3G video transmission part

The U6100 module is selected for the 3G transmission part. His maximum transmission rate of uplink and downlink under the 3G network platform can reach 384Kbps, which meets the design requirements of the vehicle transmission module. The circuit design of the 3G transmission part is shown in Figure 2.

Figure 2: Circuit diagram of the 3G transmission part

The U6100's power supply requirements are 3.6 to 4.2 V, and we supply it with 3.8 V. The U6100 provides 6 SIM card interfaces to connect SIM cards, which are compatible with various 3G formats. The U6100 provides a standard RS232 interface, USB_DM and USB_DP, which can be directly connected to the user's CPU. Since this design requires 4 USB ports, we use a USB expansion chip to expand the DM365 with only one USB port into 4, and use the DP1 and DM1 to connect to the U6100. The power supply USB VBUS is filtered by a 5 V power supply. KPD_PWR_N is the power switch of U6100. It is effective when it is pulled low. We directly ground it through a 0 ohm resistor, so the U6100 is in the working mode by default when it is turned on. EXT_RET_IN is the reset signal of U6100. When it is pulled low, it is reset. We control it through the GPIO port of DM365.

Electronic motors applications.