System Architect's Notes Issue 7: Embedded Systems and Software

An embedded system is a special computer system designed to perform a specific function or control a specific device. Different from general computer systems, embedded systems are usually embedded into other devices or systems to complete specific tasks, such as home appliances, automobiles, medical equipment, industrial control systems, etc. Embedded systems usually have the characteristics of small size, low power consumption, and high real-time requirements.

Embedded software is the software running in the embedded system, which is closely combined with the hardware. Embedded software is responsible for controlling the hardware components of the embedded system to achieve specific functions and tasks. Embedded software usually includes operating systems, drivers, applications, and more.

In an embedded system, embedded software has the following characteristics:

1. Tight integration: Embedded software is closely integrated with hardware, and is usually compiled into machine codes related to specific hardware platforms to optimize system performance and resource utilization to the greatest extent.
2. Real-time requirements: Many embedded systems require real-time response, that is, to complete tasks within a specified time. Therefore, embedded software needs to have real-time performance and be able to quickly respond to external events and real-time data.
3. Resource Constrained: Embedded systems often have limited processing power, storage space, and energy. Therefore, embedded software needs to efficiently utilize system resources to ensure system reliability and performance.
4. Reliability and stability: Embedded systems usually run continuously for a long time, which requires high reliability and stability of the system. Embedded software needs to have stability and fault tolerance to ensure that the system runs stably for a long time.

Common embedded operating systems include real-time operating systems (Real-time Operating System, RTOS), such as VxWorks, FreeRTOS, Embedded Linux, etc. Embedded software development usually uses low-level languages, such as C, C++ assembly language, etc.

The design and development of embedded systems and embedded software need to consider factors such as specific hardware platforms, real-time requirements, resource constraints, and stability. They play an important role in various fields and promote many applications of intelligence and automation.

The composition and characteristics of embedded systems

The composition and characteristics of the embedded system are as follows:

1. Processor (CPU): Embedded systems typically contain one or more dedicated processors that execute instructions and control the operation of the system. The processor can be single-core or multi-core, choose the appropriate processor according to the system requirements.
2. Memory: Embedded systems need to store information such as program codes, data, and temporary variables. Memory includes random access memory (RAM) and read-only memory (ROM), which are used to store runtime data and solidified program codes of the system.
3. Input/Output Interfaces (I/O Interfaces): Embedded systems communicate and interact with external devices, so appropriate I/O interfaces are required. These interfaces may include serial ports, parallel ports, USB, Ethernet, wireless communication, etc., for connecting external devices such as sensors, actuators, displays, and keyboards.
4. Operating System (Operating System): Embedded systems usually run on a specific operating system to manage and control system resources and tasks. Embedded operating systems need to have real-time performance and low resource consumption to meet the real-time requirements of embedded systems.
5. Application Software (Application Software): The application software of an embedded system is a software program developed for specific needs to realize specific functions of the system. Application software may include control algorithms, sensor data processing, user interface, etc.

Embedded systems are characterized by the following:

1. Real-time requirements: Many embedded systems require real-time response, that is, to complete tasks within a specified time. The system needs to respond quickly to external events within a certain time frame to meet the real-time requirements of the system.
2. Close integration of hardware and software: Embedded software is closely integrated with hardware and compiled into machine codes related to specific hardware platforms. Embedded software needs to make full use of hardware resources and cooperate closely with hardware to realize system functions.
3. Resource Constrained: Embedded systems often have limited processing power, storage space, and energy. Therefore, embedded systems need to efficiently utilize system resources to ensure system reliability and performance.
4. High reliability: Many embedded systems run continuously for a long time, which requires high reliability and stability of the system. Embedded systems need to have stability and fault tolerance to ensure that the system runs stably for a long time.
5. Size and power optimization: Embedded systems often require small size and low power consumption.

Classification of Embedded Systems

Embedded systems can be classified according to different classification criteria. The following are several common classifications of embedded systems:

1. Classification based on function:

o Real-time Embedded Systems (Real-time Embedded Systems): This system needs to respond to external events in real time, usually with strict time constraints.

o Control Embedded Systems (Control Embedded Systems): This system is used to control and monitor other devices or systems, such as industrial automation, automotive control systems, etc.

o Communication Embedded Systems (Communication Embedded Systems): This type of system is used for data communication and network connections, such as routers, modems, etc.

2. Classification based on application field:

o Automotive Embedded Systems (Automotive Embedded Systems): Used in various functions and control systems in automobiles, such as engine control units (ECUs), entertainment systems, driver assistance systems, etc.

o Medical Embedded Systems (Medical Embedded Systems): Used in medical equipment and medical instruments, such as heart monitors, blood pressure monitors, prosthetic control systems, etc.

o Industrial Embedded Systems (Industrial Embedded Systems): used in industrial automation and control systems, such as industrial robots, PLC (programmable logic controller), etc.

o Consumer Electronics Embedded Systems (Consumer Electronics Embedded Systems): used in home appliances and consumer electronics such as smartphones, smart TVs, home automation systems, etc.

3. Classification based on processor architecture:

o Microcontroller-based Embedded Systems (Microcontroller-based Embedded Systems): Using a single-chip microcomputer or microcontroller as a processor, it integrates the processor core, memory and various peripherals.

o Embedded Systems based on Embedded Processors (Embedded Systems based on Embedded Processors): Use dedicated embedded processors, such as ARM, MIPS, etc., for high-performance and complex applications.

4. Classification based on operating system:

o Real-time Operating System-based Embedded Systems (Real-time Operating System-based Embedded Systems): Use a real-time operating system (RTOS) to manage and control system resources to meet real-time requirements.

o Embedded Linux Systems (Embedded Linux Systems): Embedded systems based on the Linux kernel provide rich functions and a development environment.

These are some common classifications of embedded systems. In fact, the classification of embedded systems can also be divided in more detail according to specific needs and applications. Different types of embedded systems have different characteristics and application fields.

Embedded Software

The composition and characteristics of embedded software are as follows:

composition:

1. Application Program: A software module that implements specific functions and tasks of an embedded system. The application program is written according to the system requirements and can include control algorithms, data processing, user interface, etc.
2. Drivers (Device Drivers): software modules that interact with hardware devices. Drivers are responsible for controlling and managing hardware devices, and providing communication interfaces with devices. For example, drivers that control sensors, actuators, or handle input/output devices.
3. Operating System: Software that manages and controls the resources and tasks of a system. The operating system is responsible for allocating and scheduling system resources, and providing functions such as task management, memory management, and device management. Common embedded operating systems include real-time operating systems (RTOS) and embedded Linux.
4. Middleware: A software component that provides specific functionality to simplify and speed up the development process. Middleware may include communication protocol stacks, data storage libraries, graphics libraries, and the like. They provide commonly used functions and interfaces, enabling developers to build embedded applications more quickly.

Features:

1. Hardware dependency: Embedded software is closely integrated with hardware and needs to interact directly with hardware. The software development process needs to consider the characteristics and limitations of the hardware to ensure that the software can properly control and operate the hardware device.
2. Real-time requirements: Many embedded systems require real-time response, that is, to complete tasks within a specified time. Embedded software needs to have real-time performance and be able to quickly respond to external events and real-time data.
3. Resource Constrained: Embedded systems often have limited processing power, storage space, and energy. Therefore, embedded software needs to efficiently utilize system resources to ensure system reliability and performance.
4. Stability and reliability: Embedded systems usually need to run continuously for a long time, and have high requirements for system stability and reliability. Embedded software needs to have stability and fault tolerance to ensure that the system runs stably for a long time.
5. High degree of customization: Embedded software is usually developed for specific application requirements, so it needs to be customized according to specific needs. Developers need to understand application scenarios and requirements, and optimize software functions and performance reasonably.
6. Difficult to update and maintain: Once an embedded system is deployed into a device, it can become difficult to update and maintain the software.

Security Design for Safety-Critical Software

The security design of safety-critical software is to ensure that the software has a high degree of security in the process of design, implementation and operation, so as to prevent security threats such as malicious attacks, data leakage and system failure. Here are some common security design principles and practices:

1. Risk assessment and threat modeling: During the design phase, conduct comprehensive risk assessment and threat modeling to identify potential security threats and vulnerabilities. By analyzing the threat model, understand the attacker's behavior, attack methods and potential security vulnerabilities, and provide guidance for subsequent security design.
2. Security Requirements Analysis: Clearly define security requirements and incorporate them into the software design and development process. Security requirements should cover identity authentication, access control, data protection, vulnerability repair, etc., to ensure that the software has the necessary security performance.
3. Security architecture design: Based on the results of risk assessment and threat modeling, design a security architecture to protect software and systems. Security architecture should include security hierarchy, border defense mechanism, identity authentication and access control policies, etc., to ensure the security and reliability of the system.
4. Secure Coding Practices: During software development, secure coding practices are employed to reduce code bugs and security breaches. This includes input validation, secure programming techniques, use of secure libraries, avoiding common security vulnerabilities (such as buffer overflows, injection attacks, etc.), etc.
5. Security testing and auditing: Conduct comprehensive security testing and auditing to discover potential security loopholes and weaknesses. Including static code analysis, dynamic vulnerability scanning, security testing, security audit, etc., to ensure that the software has a high degree of security in actual operation.
6. Security Updates and Maintenance: The software is regularly updated and maintained to fix known security holes and weaknesses. Respond promptly to new security threats and take steps to prevent malicious attacks and data breaches.
7. Security Training and Awareness: Provides security training and awareness campaigns to educate software developers and users about common security threats and security best practices. Increase security awareness and help personnel follow security norms and policies.