Embedded systems are an important part of the computing field, serving as dedicated computer systems that perform specific functions within embedded objects. Embedded systems have advantages such as small size, low power consumption, high integration, and the ability for subsystems to communicate and integrate. With the development of automotive technology and the continuous advancement of microprocessor technology, embedded technology has been widely applied in automotive electronics. Currently, from body control, chassis control, engine management, active and passive safety systems to in-vehicle entertainment and information systems, all rely on the support of embedded technology.1 Development History of Automotive Embedded SystemsEmbedded systems originated in the microcomputer era, undergoing a long independent development path of single-chip microcomputers. The core of embedded systems 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) systems. Centered around 4-bit and low-end 8-bit microprocessors, integrating the CPU and peripheral circuits onto a single chip, configured with external parallel buses, serial communication interfaces, SFR modules, and Boolean instruction systems. The hardware structure and functions are relatively simple, with low processing efficiency, small storage, and a simple software structure that does not require an embedded operating system. This low-level automotive SCM system is mainly used in relatively simple control scenarios with small data processing and low real-time requirements, such as wipers, headlights, dashboards, and power windows.
Figure 1 Automotive Embedded SoC System StructureThe second stage: MCU (Micro Controller Unit) systems. Centered around high-end 8-bit and 16-bit processors, integrating more external interface functional units such as A/D conversion, PWM, PCA, Watchdog, high-speed I/O ports, etc., configured with serial buses between chips; the software structure is more complex, and the program data volume has increased significantly. The second-generation automotive embedded systems can complete simple real-time tasks and are currently widely used in automotive electronic control systems, such as ABS systems, intelligent airbags, active suspension, and engine management systems.The third stage: SoC (System of Chips) systems. Centered around high-performance 32-bit or even 64-bit embedded processors, using DSP as a coprocessor in scenarios requiring fast processing of massive discrete time signals. To meet the continuously expanding embedded application requirements of automotive systems, the processing degree is continuously improved, and storage capacity and integration are increased. Supported by embedded operating systems, it has real-time multitasking capabilities and tighter coupling with networks. Automotive SoC systems are high-end applications of embedded technology in automotive electronics, meeting the requirements of modern automotive electronic control systems for expanding functions, increasingly complex logic, and increasing communication frequency between subsystems, representing the development trend of automotive electronic technology. Automotive embedded SoC systems are mainly applied in hybrid powertrains, integrated chassis control, automotive positioning and navigation, vehicle status recording and monitoring, and other fields.2 Automotive Embedded SoC Systems2.1 Technical FeaturesAutomotive embedded SoC systems are the result of the transition of embedded systems towards high-end applications of real-time multitasking management, network coupling, and communication, greatly improving the real-time performance, 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 multitasking management, with an interrupt response time of 1 “2μs;(2) Strong storage area protection function;(3) Under the support of embedded real-time operating systems, it can reasonably schedule tasks and make full use of system resources;(4) Strong expansion capability for both hardware structure and software functions, significantly improving system integration and reducing costs;(5) Ultra-low power consumption, with static power consumption in vehicles at the level of watts;(6) Enhanced hardware anti-interference ability, adaptable to various working environments such as high temperature, humidity, vibration, and electromagnetic radiation;(7) The real-time operating system supports a multi-threaded software structure, enhancing the software’s anti-interference capability;(8) Provides powerful network communication capabilities, equipped with communication interfaces such as IEEE1394, USB, CAN, Bluetooth, or IrDA, supporting corresponding communication networking protocol software and physical layer driver software, providing fault-tolerant data transmission capabilities and greater communication bandwidth.
2.2 System StructureAutomotive embedded SoC systems consist of two main parts: hardware and software. Hardware includes embedded processing and peripheral devices, while software includes application software and operating systems. Software implements automotive electronic control strategies through data structures, algorithms, and communication protocols, while hardware provides the execution platform for software to perform specific controls.The integration of embedded SoC hardware systems is increasing, generally adopting a modular structure, as shown in Figure 1 (a). Outside the high-performance CPU core, real-time clock modules, SRAM (Static Random Access Memory), and large-capacity FLASH are expanded through IP buses, configured with CAN bus and USB communication modules, seamlessly integrating PWM output, multi-channel serial ports, A/D conversion interfaces, and unified high-speed buffers, supporting RISC technology, multi-level pipeline technology, and on-chip debugging technology. The real-time processing capability, reliability, and network communication capability of the system are greatly enhanced.Modern automotive electronic systems are gradually evolving from single control to multi-variable multi-task coordinated control, with software becoming larger and more complex, requiring embedded systems to seek new software solutions. Figure 1 (b) describes the typical structure of automotive embedded SoC system software. It adopts a modular software design based on standardized interfaces and communication protocols, with internal communication completed directly by the interaction layer, ensuring information transfer between applications. The network layer has data flow processing capabilities, serving as an intermediary interface for information exchange between different system levels, maximizing system resource integration. Embedded real-time operating systems abandon the front-and-back mode of traditional operating systems, using bus driver layers and hardware abstraction layers to manage I/O ports, reasonably allocate CPU resources, and adopt priority-based event management strategies, calling applications through API (Application Programming Interface) based on mailboxes, message queues, and semaphore mechanisms to comprehensively manage interrupts, system behaviors, and tasks.2.3 Common SoC System PlatformsTo adapt to the development trend of automotive electronic systems, semiconductor and software manufacturers worldwide have launched corresponding embedded SoC products.Famous SoC hardware platforms include: Intel’s StrongArm core processor, which has a 32-bit RISC data bus, 512KB FLASH, 256KB SRAM, and a 16-bit THUMB instruction set, supporting on-chip debugging, three-level pipeline technology, and LCD control; Motorola’s Dragonball core processor, a 32-bit RISC processor with a 16.85MHz clock frequency and 2.7MIPS processing speed, seamlessly integrating SRAM, EPROM, FLASH, LCD controllers, and PWM outputs, supporting 16-bit port DRAM; NEC’s VR core processor, a 64-bit RISC chip with a 300MHz clock and 603MIPS processing capability, integrating unified L2 cache, DRAM controllers, PCI-X bridges, and 10/100 MAC devices. Well-known SoC software platforms, namely real-time operating systems, include QNX from QNX Software Systems, VxWorks from Wind River, and PSOSystem from Integrated Systems. They are all real-time, microkernel, priority-based, message-passing, preemptive multitasking, multi-user distributed network operating systems with modular structures, running at high speeds and stability, with strong communication capabilities and scalability.Among these platforms, the StrongArm core processor, Dragonball core processor, and VxWorks operating system have good application prospects in automotive SoC systems.3 Typical Applications of SoC SystemsAutomotive embedded SoC systems fully adapt to the working environment and technical requirements of automobiles, being widely applied in automotive electronic technology. The automotive ABS/ASR/ACC integrated control system being researched by Beijing Institute of Technology is representative.The ABS/ASR/ACC integrated system is a new type of active safety system for automobiles that integrates anti-lock braking function (ABS), anti-slip driving function (ASR), and adaptive cruise function (ACC), with the system structure shown in Figure 2. It fully utilizes existing components from various subsystems, forming a sensor network composed of wheel speed sensors, engine speed sensors, throttle position sensors, accelerator pedal sensors, and detection radars, sharing controllers and execution elements. The software applies information fusion and centralized control technology to achieve anti-lock braking, anti-slip driving, and adaptive cruise functions through comprehensive adjustment of braking torque and engine output power. The control process fully considers the interrelationships between three logical modules, achieving information fusion sharing, for example, the wheel slip rate calculation of ABS and ASR can be unified, and the vehicle speed information obtained by the ACC detection radar can be used to correct the ABS reference speed.The system selects a 32-bit SoC hardware platform such as the Dragonball core MC68E328 to replace the original 16-bit ABS controller, improving hardware processing speed and anti-interference capability, with richer port resources. The onboard radar is selected from the AC110 type 77GHz millimeter-wave onboard radar produced by AutoCruise in France, with radar signal processing using DSP processors, communicating with the ABS/ASR/ACC integrated system controller via CAN bus. CAN bus transmission has the capabilities of differential data transmission, fault tolerance, and non-destructive arbitration, with transmission rates up to Mbps. Using CAN communication improves the real-time performance of the control system and facilitates the expansion of system functions and the sharing of vehicle sensor information. The CAN communication topology is shown in Figure 3.
The difficulty of software integration in the automotive ABS/ASR/ACC system lies in how to manage interrupts and coordinate the priorities of various tasks while ensuring control real-time performance. Therefore, it is essential to introduce embedded real-time operating systems in this system. Real-time operating systems can reasonably allocate software and hardware resources, perform real-time parallel processing of multiple tasks, and provide conditions for the expansion of functions such as HAC (Hill Start Assist) and EBD (Electronic Brakeforce Distribution), while supporting multi-threaded software structures, enhancing software anti-interference capabilities. The operating system selected is VxWorks, with task scheduling adopting a priority-based preemptive strategy. Based on the operating system and task priority settings, the specific ABS, ASR, and ACC control functions are implemented by calling application programs through APIs.The automotive ABS/ASR/ACC integrated system adopts the new generation of embedded technology, improving the system’s real-time performance, reliability, maintainability, and scalability.4 Development Trends of SoC SystemsAutomotive embedded SoC systems have excellent performance, and their 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 systems will develop towards FPGA/CPLD (Field Programmable Gate Array), with the system composed of fractional programmable interconnect logic units that can exchange information, with a large amount of computation completed directly by hardware, resulting in more flexible architecture and higher integration;(2) In system development, it will follow a universal open platform and unified standards for automotive electronic systems. To enhance the universality of software and hardware, accelerate development speed, and reduce costs, SoC systems urgently need to establish unified standards and development platforms. The MODISTARC specification based on the OSEK/VDX standard issued by Europe will be the development trend of automotive embedded system platforms;(3) With the development of automotive local area network technology and intelligent transportation technology, embedded SoC systems will form distributed control systems for the whole vehicle based on C-level or D-level networks and remote high-frequency communication systems based on wireless communication;(4) The application scope of embedded SoC systems will gradually expand from high-end and imported vehicles to low-end and domestically produced vehicles.Automotive embedded systems have developed rapidly in recent years. With the arrival of the post-PC era, high-end applications of embedded systems based on network communication and real-time multitasking parallel processing will become increasingly widespread. Automotive embedded SoC systems adopt high-performance 32-bit or 64-bit processors in hardware and embed real-time operating systems in software, featuring diverse functions, high integration, network communication, rapid development, and low cost, with broad applications in automotive electronic control and vehicle network communication systems, making them the best solution for future automotive electronics.
Source: Electronic Enthusiasts Network
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