Application and Development of Automotive Embedded SoC System
The embedded system is an important part of the field of pan-computing, and it is a special computer system that accomplishes a specific function in the embedded object host system. Embedded systems have the advantages of small size, low power consumption, high integration, and communication and integration between subsystems. With the development of automotive technology and the continuous progress of microprocessor technology, it has been widely used in automotive electronic technology. At present, from body control, chassis control, engine management, active and passive safety systems to in-vehicle entertainment, information systems are inseparable from the support of embedded technology.
1 Development history of automotive embedded systems
Embedded systems were born in the era of microcomputers, and have experienced a long road of independent development of single-chip microcomputers [2]. The core of the embedded system is the embedded microprocessor. Similar to the development of embedded microprocessors, automotive embedded systems can also be divided into three stages of development:
The first stage: SCM (Single Chip Microcomputer) system. With 4-bit and low-grade 8-bit microprocessor as the core
Figure 1 Automotive embedded SoC system structure
The second stage: MCU (Micro Controller Unit) system. With high-end 8-bit and 16-bit processors as the core, it integrates more external interface functional units, such as A / D conversion, PWM, PCA, Watchdog, high-speed I / O ports, etc., and configures the serial bus between the chips; The software structure is relatively complex, and the amount of program data has increased significantly. The second-generation automotive embedded system can complete simple real-time tasks, and is currently the most widely used in automotive electronic control systems, such as ABS systems, intelligent airbags, active suspensions, and engine management systems.
The third stage: SoC (System of Chips) system. Taking the 32-bit or even 64-bit embedded processor with extremely high performance as the core, DSP is used as a co-processor in the occasions requiring fast processing of massive discrete-time signals. In order to meet the ever-expanding needs of embedded applications in automotive systems, the level of processing is continuously improved, and storage capacity and integration are increased. With the support of embedded operating system, it has more real-time processing capabilities and is more closely coupled with the network. The automotive SoC system is a high-end application of embedded technology in automotive electronics. It meets the requirements of the continuous expansion of modern automotive electronic control system functions, the complexity of logic, and the increasing frequency of communication between subsystems. It represents the development trend of automotive electronic technology. Automotive embedded SoC systems are mainly used in the fields of hybrid powertrain, integrated chassis control, vehicle positioning and navigation, vehicle status recording and monitoring.
2 Automotive embedded SoC system
2.1 Technical characteristics
Automotive embedded SoC system is the product of the transition from embedded systems to high-end applications of real-time multi-task management, network coupling and communication, which greatly improves the real-time, reliability and intelligence of automotive electronic systems. In addition to the common characteristics of ordinary embedded systems, it also has the following advantages:
(1) Strong support for real-time multi-task management, interrupt response time 1 ~ 2μs;
(2) Has a strong storage area protection function;
(3) Under the support of embedded real-time operating system, it can reasonably schedule tasks and make full use of system resources;
(4) The hardware structure and software functions have strong expansion capabilities, the system integration is greatly improved, and the cost is reduced;
(5) Ultra-low power consumption, the static power consumption of the car is Haowa class;
(6) The anti-interference ability of the system hardware is enhanced, adapting to various working environments such as high temperature, humidity, vibration and electromagnetic radiation;
(7) The real-time operating system supports the software multi-thread structure, which enhances the system's software anti-interference
(8) Provide powerful network communication functions, with IEEE1394, USB, CAN, Bluetooth or IrDA communication interfaces, support the corresponding communication networking protocol software and physical layer driver software, provide fault-tolerant data transmission capabilities and greater communication bandwidth.
2.2 System structure
Automotive embedded SoC system is composed of hardware and software. The hardware includes embedded processing and peripheral devices, and the software includes application software and operating system. Software implements automotive electronic control strategies through data structures, algorithms, and communication protocols, while hardware provides a platform for the software to execute specific controls.
The embedded SoC hardware system is becoming more and more integrated, generally with a modular structure, as shown in Figure 1 (a). Expand the real-time clock module, SRAM (static random memory) and large-capacity FLASH outside the core of the high-performance CPU through the IP bus, configure the CAN bus and USB communication module, seamlessly integrate PWM output, multi-channel serial port, A / D conversion interface and unification The cache memory supports RISC technology, multi-stage pipeline technology and on-chip debugging technology. The real-time processing capability, reliability and network communication capabilities of the system are greatly enhanced.
Modern automotive electronic systems have gradually evolved from single control to multi-variable multi-task coordinated control. The software is getting larger and more complex, making embedded systems need to find new software solutions. Figure 1 (b) describes the typical structure of automotive embedded SoC system software. It uses a modular software design based on standardized interfaces and communication protocols. The internal communication of the system is directly completed by the interaction layer to ensure the transmission of information between applications. The network layer has data flow processing capabilities and is an intermediate interface for information exchange between different system layers, which can maximize the integration of system resources. The embedded real-time operating system abandons the front and back mode of the traditional operating system, uses the bus driver layer and the hardware abstraction layer to manage I / O ports, allocates CPU resources reasonably, adopts a priority-based event management strategy, and uses API (application program interface) Call the application program to manage interrupts, system behaviors, and tasks in a comprehensive manner based on mailboxes, message queues, and semaphore mechanisms.
2.3 Commonly used SoC system platforms
In order to adapt to the development trend of automotive electronic systems, semi-heterogeneity and software manufacturers in various countries have launched corresponding embedded SoC products.
Famous SoC hardware platforms include: Intel's StrongArm core processor, with 32-bit RISC data bus, 512KB FLASH, 256KB SRAM and 16-bit THUMB instruction set, support on-chip debugging, three-stage pipeline technology and LCD control; Motorola The company's Dragonball core processor, which is a 32-bit RISC processor, has a clock frequency of 16.85MHz and a processing speed of 2.7MIPS, seamlessly integrates SRAM, EPROM, FLASH, LCD controller and PWM output, supports 16-bit port DRAM; NEC The company's VR core processor, which is a 64-bit RISC chip, has a 300MHz clock and 603MIPS processing level, integrated unified L2 cache memory, DRAM controller, PCI-X bridge and 10 / 100MAC device. Well-known SoC software platforms, real-time operating systems include "QNX QNX, Wind River Vxworks and Integrated System PSOSystem. They are all real-time, micro-core, priority-based, messaging, preemptive multitasking, multi-user The distributed network operating system has a modular structure, the core runs at high speed and stability, and the communication ability and expansion and cutting ability are very strong.
In the above platform, the StrongArm core processor and Dragonball core processor and the VxWorks operating system have good application prospects in the automotive SoC system.
3 Typical application of SoC system
The automotive embedded SoC system fully adapts to the working environment and technical requirements of automobiles, and is widely used in automotive electronic technology. Among them, the automobile ABS / ASR / ACC customized control system that Beijing University of Technology is studying is representative.
The ABS / ASR / ACC integrated system is a combination of brake anti-lock braking function (ABS), drive anti-skid function (ASR) and adaptive cruise function
The system selects a 32-bit SoC hardware platform such as the MC68E328 at the core of the Dragon ball to replace the original 16-bit ABS controller, which improves the hardware processing speed and anti-interference ability, and the port resources are more abundant. The vehicle-mounted radar uses the AC110 type 77GHz millimeter-wave vehicle Xida produced by France AutoCruise. The radar signal is processed by a DSP processor and communicates with the ABS / ASR / ACC integrated system controller through the CAN bus. CAN bus transmission has the capability of data differential transmission and reception, fault tolerance and non-destructive arbitration, and the transmission rate is up to Mbps. The use of CAN communication improves the real-time nature of the control system and provides convenience for system function expansion and vehicle sensor information sharing. The CAN communication topology is shown in Figure 3.
The difficulty of the integration of automotive ABS / ASR / ACC system software is: how to perform interrupt management and coordinate the priority of various tasks under the premise of ensuring real-time control, so it is necessary to introduce an embedded real-time operating system in the system. The real-time operating system can reasonably allocate software and hardware resources, perform multi-task parallel processing in real time, and provide conditions for the system to expand functions such as HAC (elevation assist system) and EBD (electronic braking force distribution system), while supporting multi-threaded software Structure, enhance the software anti-interference. The operating system uses VxWorks, and the task scheduling adopts a preemptive strategy based on priority. Based on the operating system and task priority settings, specific ABS, ASR, and ACC control functions are implemented by API calling application programs.
Automobile ABS / ASR / ACC integrated system uses a new generation of embedded technology, which improves the real-time, reliability, maintainability and scalability of the system.
4 Development trend of SoC system
Automotive embedded SoC system has excellent performance, and its superiority is gradually recognized by the automotive industry. In the future, automotive embedded SoC systems will show the following development trends:
(1) Automotive embedded SoC system will be developed in the direction of FPGA / CPLD (Online Programmable Gate Array). The system is composed of split programmable interconnected logic units. Information can be exchanged between the units. A large number of operations are completed directly by hardware. More flexible architecture and higher integration;
(2) Follow the universal open platform and unified standards for automotive electronic systems in system development. In order to improve the versatility of software and hardware, speed up development and reduce costs, SoC systems urgently need to build a unified standard and development platform. The MODISTARC specification based on the OSEK / VDX standard issued by Europe will be the development trend of automotive embedded system development platforms;
(3) With the development of automotive LAN technology and intelligent transportation technology, the embedded SoC system will form a vehicle-wide distributed control system based on C-level or D-level networks and remote high-frequency network communication based on wireless communication system;
(4) The application scope of the embedded SoC system will gradually expand from high-end cars and imported cars to low-end cars and domestic cars.
Automotive embedded systems have developed very rapidly in recent years. With the advent of the post-PC era, embedded high-end applications based on network communications and real-time multitasking parallel processing will become more widespread. Automobile embedded SoC system adopts 32-bit or 64-bit high-performance processor in hardware, embeds real-time operating system in software, has the characteristics of versatility, high integration, communication network, rapid development and low cost. Control and vehicle network communication systems have a wide range of applications and are the best solution for future automotive electronics.
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Current rating
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