Application of TMS320VC5402 in Automobile Anti-collision Warning Radar

　　In the past decade, many well-known automobile companies in the United States, Japan and Europe have invested huge amounts of money to successfully develop two types of automobile anti-collision radar systems: single pulse and frequency modulated continuous wave at three frequencies of 24GHz, 60GHz and 76.5GHz. These two types of radar systems have been used in high-end cars, but have not been widely popularized.

　　In recent years, the emergence of low-cost high-performance DSP chips has greatly promoted the development of electronic products in the world, making it possible to realize and popularize low-cost and high-performance anti-collision radar for automobiles. This paper proposes a principle scheme for the signal processing part of anti-collision warning radar for automobiles , which uses high-performance DSP chip TMS320VC5402 as digital signal processing task, CPLD to complete control and interface logic, and single-chip microcomputer AT89C51 to provide human-machine channel and other coordinated work , and briefly introduces its realization circuit and system structure.

　　1 Introduction to TMS320VC5402

　　TMS320VC5402 is a new product in TI's C54x series of fixed-point DSP chips. It concentrates the advantages of the earlier products in this series and provides many new functions, making development and use more convenient. C5402 has a flexible instruction system and operating performance. It can select mnemonic instructions or arithmetic instructions as programming instructions, and supports separate or mixed programming of assembly language and C language. C5402 adopts an improved Harvanl processing structure and instruction pipeline operation. The calculation and processing speed is very high, and the system single instruction cycle can reach 10ns. 16k of RAM is provided on the chip for program and data storage, and its maximum expandable addressing space is 1M bytes. The McBSP serial port and DAM data transmission method provided by C5402 greatly facilitate its application and development in the field of communications. C5402 has become the current mainstream product for language and static image processing due to its high performance and price:

　　(1) Fast computing speed. The instruction cycle is 10ns and the computing power is 100 MIPS.

　　(2) Powerful addressing capability. 1M×16-bit maximum addressable external storage space, built-in 16K×16-bit RAM, 4K×16-bit ROM.

　　(3) Optimized CPU structure. It has a 40-bit arithmetic logic unit, two 40-bit accumulators, two 40-bit adders, a 17×17 multiplier and a 40-bit barrel shifter. It has four internal buses (three 16-bit data memory buses and one program memory bus) and two address generators.

　　(4) Intelligent peripherals. In addition to standard serial ports and time division multiplexing (TDM) serial ports, the TMS320VC5402 also provides an automatic buffered serial port BSP and an HPI interface for communicating with an external processor. The BSP can provide 2K-word data buffer read and write capabilities, thereby reducing the processor's additional overhead. The BSP has a maximum data throughput of 100 Mbit/s and can operate at full speed even in IDLE mode. The HPI can directly interface with an external standard microprocessor.

　　(5) Low power mode. The TMS320VC5402 core power supply is 1.8V, the IO power supply is 3.3V, and the three low power modes (IDLE1, IDLE2, and IDLE3) can save the power consumption of the DSP, which is particularly suitable for battery-powered systems.

　　(6) Small size. 144-pin LQFP package.

　　(7) Easy development. JTAG scan simulation interface.

　　JTAG was originally used to test chips. The basic principle of JTAG is to define a TAP (Test Access Port) inside the device to test internal nodes through a dedicated JTAG test tool. JTAG testing allows multiple devices to be connected in series through the JTAG interface to form a JTAG chain, which can test each device separately. Nowadays, the JTAG interface is also commonly used to implement ISP (In-System Programmable) and program devices such as FLASH.

　　TMS320VC5402 has been widely welcomed by users in the industry as soon as it was launched due to its unique advantages of high performance, low power consumption and low price. This is also the main reason why we chose it as the digital signal processor of the automotive anti-collision warning radar.

　　2. Introduction to the design concept and performance parameters of anti-collision radar

　　The main design concept of the car anti-collision warning radar is to take into account that vicious traffic accidents such as head-on collisions and rear-end collisions often occur under complex road conditions, poor visibility, and driver fatigue. Therefore, its most important design purpose is to detect potentially dangerous targets in front as early as possible and to give an alarm in time to remind the driver to take corresponding handling actions. Since the signals received by the Doppler sensor are very complex during the driving process of the car, in order to detect, classify, track, judge and alarm multiple targets in front of the car in a very small field of view, a large number of complex real-time digital signal processing operations must be performed. Therefore, we use the high-performance DSP chip TMS320VC5402 to complete this series of complex algorithms; at the same time, in order to improve the flexibility and reliability of the system, we use CPLD devices to complete the various control and interface functions required by the system.

　　The main technical parameters of the radar are as follows:

　　(1) It is an all-weather warning radar system that can operate normally in various adverse weather environments and complex road conditions such as fog, rain, snow, and night.

　　(2) Working band: microwave or millimeter wave.

　　(3) Transmitter type: Gunn diode.

　　(4) Transmitter output power: 20mW.

　　(5) Antenna horizontal beam width: 6°.

　　(6) Operating distance: 200m.

　　(7) Update rate: 20 times/second.

　　Since TMS320VC5402 has strong capabilities in numerical algorithms, but is not good at transaction scheduling, we use an AT89C51 to cooperate with it and adopt a master-slave structure processing method. TMS320VC5402 completes A/D sampling and a series of processing related to numerical calculations, including clutter filtering, time domain windowing, FFT, power spectrum estimation, spectrum peak search, target extraction, target tracking, etc.; the single-chip microcomputer completes transaction scheduling, human-machine interface, display and danger alarm tasks. The data exchange between TMS320VC5402 and AT89C51 adopts parallel mode. The system signal processing principle block diagram is shown in Figure 1. [page]

    In Figure 1, the CPLD mainly completes four tasks: (1) Address decoding of each port, including the start-up and reading of AD775, address generation of each flag unit, etc. (2) Data exchange between TMS320VC5402 and the single-chip microcomputer. (3) Control logic of AD775. AD775 is an 8-bit parallel A/D device with a sampling frequency of up to 20MHz produced by A/D Company. It is very convenient to control. After starting the A/D, the BIO port of TMS320VC5402 queries the end flag of AD775 to read the valid conversion data. (4) Interface between TMS320VC5402 and FLASH EPROM. The application of CPLD greatly simplifies the circuit design of the entire system, and it has a compact structure, coordinated and orderly, easy debugging, and reliable performance. Figure 2 is a block diagram of the main functions inside the CPLD.

　　4 Software Design

　　The main tasks that TMS320VC5402 needs to complete are: (1) Start A/D and read the converted data. (2) Target extraction, including data preprocessing (clutter filtering, time domain windowing), power spectrum estimation, spectrum peak search, target classification, dangerous target identification and tracking, etc. (3) Exchange data with AT89C51.

　　The MCU mainly completes tasks such as exchanging data with DSP, setting thresholds, human-machine interface, judging alarms, etc. We divide these contents into different subroutines and design them by module, which is very convenient for debugging and expansion. The following is the flowchart of TMS320VC5402 software programming we give, as shown in Figure 3.

　　The automotive anti-collision radar system is not only low-cost, small in size and highly reliable, but also uses advanced digital signal processing algorithms to make it highly sensitive, with a low false alarm probability, and can detect dangerous targets in a timely and accurate manner.