The automotive industry utilizes reconfigurable hardware technology to flexibly integrate vehicle functions.
Today's car manufacturers are adding more and more advanced functions to the automotive electronic control unit (ECU) to improve the driving experience and enhance safety, and of course expect to exceed the sales of similar products. Under such circumstances, the Automotive Open System Architecture (AUTOSAR) program and the functional safety international standard ISO26262 are rapidly becoming the technical and architectural basis for automotive ECU design.
In order to meet the increasing functional requirements of new models, the density of automotive electronic products continues to increase, and FPGA manufacturers are also constantly introducing larger devices. These devices can integrate all applications, and compared with previous generation devices, lower power consumption and more competitive prices. This trend means that reconfigurable computing technology will be further promoted and applied in the automotive industry.
We introduced a groundbreaking method that uses programmable FPGA devices instead of MCU-based platforms as the basis for ECUs, and designs an automotive ECU that can meet both AUTOSAR and ISO 26262 standards. Our design approach fully explores the key features of reconfigurable hardware, such as parallelism, customizability, flexibility, redundancy, and versatility. After the conceptual design is completed, we hope to implement the design in the prototype. For this reason, the Xilinx Zynq ™ -7000 scalable processing platform has become an ideal choice. This FPGA platform combines an ARM® dual-core Cortex ™ -A9 MPCore hard processor and a 28 nm Xilinx 7 series programmable logic device with dynamic partial reconfiguration, which not only fully meets the required requirements, but also It is also equipped with on-chip communication controllers commonly used in vehicle networks such as CAN and Ethernet.
Emerging applications
At present, the computing power of automobiles is distributed by means of ECUs interconnected through a communication network. In the next few years, due to the rise of new applications in motor vehicles, such computing power is expected to be further improved. These new applications include safety and driver assistance functions, inter-vehicle communication functions, comfort and control functions, in-vehicle entertainment functions, and numerous hybrid electric technologies. There is no doubt that the number of vehicle electronic devices is expected to increase. According to analysts' forecasts, the size of the automotive application semiconductor market will grow at an average annual compound growth rate (CAGR) of 8% over the next five years. One of the fastest growing market segments involves microcontrollers (MCUs) and programmable logic devices, such as field programmable gate arrays (FPGAs).
While the number and advanced nature of in-vehicle functions are increasing, the design and management of these systems are becoming more and more complex. Automakers believe that it is necessary to adopt effective methods to solve this problem. The result is that today's two major standards, AUTOSAR and ISO 26262, are affecting the architecture, design, and deployment of actual automotive ECU hardware and software systems (see sidebar).
In 2003, the AUTOSAR standard jointly developed by a number of car manufacturers aimed to define a standard system software architecture for ECUs distributed in vehicles. The purpose of the ISO 26262 standard is to focus on functional safety, which is essentially to avoid or detect and deal with failures, so as to mitigate the impact of failures and prevent violations of any existing system safety goals. With the introduction of new safety-critical functions (such as driver assistance or dynamic control), functional safety has become one of the key issues in automotive development. The ISO 26262 standard was approved and entered into force in 2011 and can support the safe development of software and hardware.
Therefore, the entire ECU design and development process is managed by standards that require systematic processes. Our job is to design a cost-effective embedded computing platform that uses reconfigurable hardware technology to achieve an optimized system architecture.
system structure
The AUTOSAR and ISO 26262 standards are mainly focused on the perspective of software development, and are oriented towards computing platforms based on microcontroller units. However, the combination of hardware / software design and the application of reconfigurable computing technology can bring many advantages to this field. Although standard MCUs are often the best choice for automotive ECU hardware platforms, as the cost of new FPGAs continues to decrease, and some FPGA products have integrated hard core processors, FPGA devices have also become worthy of widespread application in this market. The ideal solution. In addition, the trend of continuously integrating new embedded functions in automobiles has also raised the demand for parallel computing architectures. This is particularly evident in today's in-vehicle infotainment field, where high-speed digital signal processing is opening the door to FPGA technology. Programmable logic vendors like Xilinx and EDA tool vendors like MathWorks have already shown a clear interest in this area.
In order to take full advantage of reconfigurable hardware in automotive applications, we will focus on one of the most important ECUs in the automotive computing network that deploys end-user functions-the "body controller module", and demonstrate this through use cases. The potential of technology. The ECU is also known as the "body domain controller" and is responsible for integrating and controlling the main electronic body functions in the vehicle, such as windshield wipers / water spray systems, lights, window shakers, engine ignition / turn-off, and exterior rearview Mirror and central lock. Our goal is to design an AUTOSAR-compliant ECU system equipped with safety-critical functions on the FPGA platform.
Actual situation
If car manufacturers want to cost-effectively manage increasingly complex vehicle functions, standardization of the ECU system architecture advocated by AUTOSAR is the only way. It can achieve a high degree of integration of various functions distributed in the ECU and reuse of software components. The main purpose of AUTOSAR is to define a unified ECU architecture to separate hardware and software. In this way, AUTOSAR can improve the reuse of software by defining hardware-independent interfaces. In other words, if a software component written in accordance with the AUTOSAR standard, as long as it is correctly integrated into the operating environment that complies with the AUTOSAR standard, it can be run on a microcontroller of any manufacturer.
This feature gives automakers more flexibility. Due to the inherent plug-and-play nature of the AUTOSAR standard, car manufacturers can transparently replace various versions of the same software module developed by different suppliers on the entire car platform, and will not cause negative effects on the remaining functions of the car. . The final hardware and software implementation is highly independent of each other. This separation is achieved by interconnecting the abstraction layers through standard software APIs. Figure 1 is an exploded view of the functional layer defined by AUTOSAR.
Figure 1 AUTOSAR layered model from MCU to application layer
The black layer at the bottom indicates the hardware layer or physical layer, which is composed of the MCU itself (that is, the CPU and some standard peripherals connected to it). Above the microcontroller is the basic software (BSW), which is divided into three layers: a pink microcontroller abstraction layer (MCAL), a green ECU abstraction layer (ECUAL) and a complex driver, and a purple service layer (SRV). These three layers are organized to form multiple columns or protocol stacks (memory, communication, input / output, etc.).
Close to the hardware components is the microcontroller abstraction layer. As the name suggests, this layer is an abstraction of the MCU. The purpose of this layer is to provide a hardware independent API, which is responsible for processing the hardware peripherals in the microcontroller. The upper layer of the microcontroller abstraction layer is the ECU abstraction layer, which is responsible for abstracting other smart devices on the ECU development board, generally directly contacting the MCU (for example, system voltage regulators, intelligent switching controllers, configurable communication transceivers, etc.) . The next third layer is the service layer. This layer is basically hardware independent and its role is to handle the different types of background services required. Such as network service, NVRAM processing or management of system watchdog. Through these three layers, AUTOSAR defines a set of basic software functions. This set of software functions supports all functions of each high-level abstraction layer of the automotive ECU under a specific hardware platform.
The fourth layer is the operating environment (RTE), which provides communication services for application software. It consists of a set of signals (transmitter / receiver ports) and services (client and server ports) that can be accessed from the upper BSW layer and application layer (APP). The RTE abstracts applications from basic software and clearly outlines the software protocol stack architecture that separates common exchangeable software code (APP) and specific hardware-related code (BSW). In other words, RTE can separate software applications from hardware platforms. Therefore, all software modules running on RTE are platform independent.
On top of RTE, through the application layer, the software architecture changes from layering to component-based. The functions are mainly encapsulated in software components (SWC). Therefore, the completion of the standardization of the AUTOSAR software component interface is the central link to support the scalability and portability of ECUs with different functions across different vehicle platforms. In addition to complex drivers, the AUTOSAR standard clearly specifies the API and features of these components. SWC communicates with other modules (inter-ECU or internal) only through the operating environment.
As ECUs continue to integrate more and more functions, FPGA devices have become a smart alternative to single-core or multi-core MCUs. By grasping the different levels of AUTOSAR as a whole, we can foresee the advantages that designers can bring when deploying this architecture in programmable logic. The following will introduce in more depth how our design implements a solution based on custom static hardware (FPGA technology based on flash memory or SRAM), and then extends this method to a runtime reconfigurable hardware implementation solution (based on SRAM Part of the reconfigurable FPGA).
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