Real Time and Embedded Systems - University of Gondar - PDF

University of Gondar Department of Computer Science Real time and embedded system  Chapter-3 Software Frameworks for Real-time and Embedded Systems Real-Time Operating Systems AA preencoded.png Time-Critical Applications 1 Strict deadlines 2...

University of Gondar Department of Computer Science Real time and embedded system  Chapter-3 Software Frameworks for Real-time and Embedded Systems Real-Time Operating Systems AA preencoded.png Time-Critical Applications 1 Strict deadlines 2 Deterministic behavior System must respond within specific Predictable response timeframes. times and performance. 3 High reliability Minimize errors and ensure system stability. preencoded.png Functionality of a Real-Time OS Task Management Resource Management Communication Creating, scheduling, and Allocating and controlling system Facilitating communication managing tasks. resources. between tasks. preencoded.png Features of a Real-Time OS Preemptive Scheduling Real-Time Clock Interrupting tasks to Precise timekeeping for prioritize higher-priority accurate scheduling. ones. Interrupt Handling Memory Management Responding to external Optimizing memory usage events promptly. for efficient operation. preencoded.png Microprocessor Support General-purpose Wide range of applications, microprocessors flexible but less efficient for real-time. Real-time microprocessors Optimized for timing accuracy and responsiveness, specialized for real-time systems. preencoded.png Inter-Process Communication Shared Memory Direct access to shared memory regions. Message Queues Asynchronous communication through queues. Semaphores Synchronization mechanisms for shared resources. preencoded.png Real-Time Task Scheduling Rate Monotonic 1 Prioritizes tasks with the highest frequency. Earliest Deadline First 2 Schedules tasks based on their deadlines. Dynamic Priority Scheduling 3 Adjusts priorities based on task requirements. preencoded.png Dynamic Task Allocation Resource Allocation Assigning resources to tasks dynamically. Task Migration Moving tasks between processors for load balancing. Real-time Adaptation Adapting to changing conditions and requirements. preencoded.png  Chapter-3 Real time operating system(RTOS) ▪ A general-purpose OS is system software that manages user applications and the hardware resources of a computer, defining rules and programming interfaces that allow a program to request OS services and interact with the rest of the system. ▪ A general-purpose OS that implements some real-time features can be used for soft real-time applications.  Chapter-3 Real time operating system(RTOS) ▪ For hard real-time systems, however, a RTOS, would be necessary in order to respond with bounded response time to external events which are typically associated with hard timing constraints (deadlines). ▪ The key characteristic of an RTOS is that its response time to an event should be deterministic (or predictable). ▪ In other words, an RTOS should provide reliable mechanisms, such as real- time signals, preemptive scheduling, and nonblocking interposes communications, for enabling a deterministic-response. Synchronization Techniques Essential for coordinating actions in parallel systems. AA preencoded.png Necessity of Synchronization Ensures consistent data access in shared environments. 1 Data Integrity 2 Resource Management 3 Performance Prevents corruption of data Avoids conflicts when Optimizes concurrency by by multiple processes. accessing shared resources. coordinating tasks. preencoded.png Types of Synchronization Varied approaches based on different requirements. Semaphores Mutexes Binary or counting signals Exclusive locks for critical for resource control. sections of code. Monitors Condition Variables Abstractions with Allow threads to wait for synchronized methods specific conditions. and data. preencoded.png Centralized Clock Synchronization Single time source for all systems. Time Server Clients Challenges Acts as a reference clock. Request time updates from the server. Single point of failure, latency impact. preencoded.png Distributed Clock Synchronization No single source, consensus among peers. Message Exchange Nodes exchange time information. Algorithm Computes time corrections based on delays. Synchronization Adjusts local clocks to align with peers. preencoded.png Real-Time Applications Synchronization essential for critical tasks. RTOS Semaphores Queues Events Support Resource Message Signal- control passing based communica tion preencoded.png  Chapter-3 Real time operating system(RTOS) ▪ Real-Time OS (RTOS)  Chapter-3 Semaphore ▪ Semaphore ▪ When multiple tasks gain access to a shared resource at the same time, the integrity of the resource is endangered like multithreading example ▪ where two consecutive reads of the shared variable can be different. The violation of data integrity can happen to multiple processes as well. ▪ The block of code that accesses a shared resource is often called a critical section. ▪ Two critical sections that access the same exclusive resource are called contending critical sections. ▪ We obviously need some tools to protect shared resources such that no two contending critical sections can be executed at the same time. ▪ One such tool is called a semaphore  Chapter-3 Semaphore ▪ A semaphore is a synchronization mechanism used in concurrent programming to manage resource sharing and coordinate tasks in multitasking systems. ▪ It acts as a signaling mechanism that allows threads or processes to communicate and synchronize access to shared resources like memory, files, or hardware components.  Chapter-3 Semaphore ▪ Therefore , semaphore is nothing but a value or variable or data which can control the allocation of a resource among d/f tasks in a parallel programming environment. ▪ So, Semaphores are a useful tool in the prevention of race conditions and deadlocks; however, their use is by no means a guarantee that a program is free from these problems. ▪ Semaphores which allow an arbitrary resource count are called counting semaphores, whilst semaphores which are restricted to the values 0 and 1 (or locked/unlocked, unavailable/available) are called binary semaphores.  Chapter-3 Semaphore ▪ Semaphore Semaphores Control access to shared resources. Initialization 1 Sets the semaphore's initial value. Wait 2 Decrements the semaphore value, blocking if negative. Signal 3 Increments the semaphore value, waking up waiting threads. preencoded.png  Chapter-3 Semaphore ▪ In general semaphore is an OS kernel object that allows mutually exclusive access to shared resources. ▪ Types of Semaphore ✓Binary Semaphores, ✓Counting Semaphores and ✓Mutexes  Chapter-3 Semaphore Usage of Semaphore in Real-Time Systems 1. Resource Management: 1. Ensures exclusive access to hardware resources (e.g., printers, ADCs, I2C buses). 2. Controls access to shared memory regions or data buffers. 2. Task Synchronization: 1. Coordinates execution of tasks in response to real-time events. 2. Ensures tasks wait for a signal or a specific condition before proceeding (e.g., waiting for a sensor input). 3. Interrupt Handling: 1. Synchronizes tasks with interrupt service routines (ISRs) to process critical events. 4. Deadlock Prevention: 1. Prevents two or more tasks from endlessly waiting for each other to release resources. 5. Task Prioritization: 1. Allows higher-priority tasks to preempt lower-priority ones when accessing shared resources  Chapter-3 Semaphore Examples in Real-Time and Embedded Systems 1. Real-Time Operating System (RTOS): 1. Many RTOSs like Free RTOS provide semaphore APIs to synchronize tasks and manage resource sharing. 2. Multitasking in Embedded Systems: 1. In a system where multiple threads access a shared display, a semaphore ensures that only one thread updates the display at a time. 3. Producer-Consumer Problem: 1. A semaphore ensures that a producer thread does not overwrite data before a consumer thread processes it. 4. Sensor Data Handling: 1. A semaphore signals when new data is available from a sensor, allowing a task to process the data efficiently. 5. Motor Control in Robotics: 1. Semaphores can synchronize tasks controlling multiple motors, ensuring safe and coordinated movements.  Chapter-3 Semaphore Advantages of Semaphores in Embedded Systems 1. Lightweight and efficient for resource synchronization. 2. Prevents race conditions and data corruption. 3. Promotes modular and maintainable code in multitasking environments. Limitations 1. Requires careful design to avoid deadlocks and priority inversion. 2. Debugging issues like semaphore leaks or incorrect usage can be challenging. Semaphores play a critical role in ensuring the reliability and responsiveness of real-time and embedded systems. Real-Time Operating Systems A specialized type of operating system. Designed for time-critical applications. A preencoded.png Time-Critical Applications 1 Strict deadlines 2 Deterministic behavior System must respond within specific Predictable response timeframes. times and performance. 3 High reliability Minimize errors and ensure system stability. preencoded.png  Chapter-4 Embedded Systems Design Issues  Chapter-4 memory management - Embedded Systems Design Issues Developing for a diverse range of devices. AA by Abebaw Agegn preencoded.png Design Challenges 1 Resource Constraints 2 Real-Time Constraints Requirements Limited processing power, Ensuring fast and power, memory, and energy. predictable responses. energy. 3 Environmental Factors 4 Cost and Complexity Balancing affordability with Temperature, humidity, and with performance. and vibrations impact design. preencoded.png Hardware Development and Constraints Choosing the Right Processor Memory Optimization Interfacing with Peripherals Processor Efficient use of limited memory Sensors, actuators, and Balancing power consumption and resources. communication modules. and processing speed. preencoded.png Software Development Real-Time Operating Systems (RTOS) Scheduling tasks and managing resources. Device Drivers Interfacing with hardware components. Application Logic Implementing specific functionalities. preencoded.png Memory Management Dynamic Memory Memory Fragmentation Allocation Fragmentation Allocating memory at runtime. Avoiding memory waste and and improving efficiency. Memory Protection Preventing unauthorized access. preencoded.png Reliability and Fault Tolerance Redundancy Error Detection Recovery Mechanisms Multiple Monitoring for Restoring components errors functionality preencoded.png Software Development and and Debugging 1 Code Development Creating and testing embedded software. Debugging Tools 2 Using specialized tools for analysis and troubleshooting. Testing and Validation 3 Ensuring correct functionality and reliability. preencoded.png Future Trends and Innovations Cloud Connectivity Artificial Intelligence (AI) Remote management and data Advanced decision-making and data processing. automation. Internet of Things (IoT) Cybersecurity Connecting devices and enabling Protecting against threats and enabling communication. vulnerabilities. preencoded.png  Chapter-4 memory mgt -  Chapter-4 memory mgt -  Chapter-4 memory mgt -  Chapter-4 memory mgt Note ▪ Embedded systems often have limited memory ▪ RTOS: each task needs memory space for its stack ▪ The first method for determining how much stack space a task needs is to examine your code ▪ The second method is experimental ▪ Fill each stack with some recognizable data pattern at startup, run the system for a period of time  Chapter-4 memory mgt Program/code Memory: ▪ Limit the number of functions used ▪ Check the automatic inclusions by your linker: may consider writing own functions. ▪ Include only needed functions in RTOS ▪ Consider using assembly language for large routines  Chapter-4 memory mgt Data Memory Consider using more static variables instead of stack variables On 8-bit processors, use char instead of int when possible  Chapter-4 Hardware development In order to meet the user requirements, we consider a simple hardware design as specified below: The system has a microprocessor with an analog input interface. ✓ The system has a temperature sensor. ✓ The system has a status register SSR with a flag bit (s_flag) that indicates whether the sensor is on or off. It also has a data register SDR for storing the latest measure digitized from the analog input from the sensor. ✓ The system has an LCD for showing the current body temperature. ✓ The system has a buzzer circuit. It starts buzzing if the temperature measure has not changed ✓ The system has a group of three pushbuttons. The left button allows a user to toggle between degree Fahrenheit mode and degree Celsius mode. The middle button allows a user to stop the buzzer, if it is buzzing, or to start a new measure, if the buzzer is not buzzing. The right button allows the user to turn on/off the thermometer. ✓ The three buttons share one status register BSR, containing flags that indicate the status of the buttons and the buzzer.  Chapter-4 Hardware development Hardware concurrency  Chapter-4 Hardware development Hardware concurrency  Chapter-4 Hardware development Hardware concurrency  Chapter-4 software/firmware development Software design  Chapter-4 software/firmware development Software design  Chapter-4 software/firmware development Software design  Chapter-5 Real-time Communication  Chapter-5 Real time communication over internet Communication Interface: Communication interface is essential for communicating with various subsystems of the embedded system and with the external world The communication interface can be viewed in two different perspectives; namely; 1. Device/board level communication interface (Onboard Communication Interface) 2. Product level communication interface (External Communication Interface)  Chapter-5 Real time communication over internet  Chapter-5 Real time communication over internet  Chapter-5 Internet of things (IoT) The description of the Internet of Things is related to different definitions used by several groups for promoting the particular concept in the whole world. According to the Internet Architecture Board’s (IAB) definition, IoT is the networking of smart objects, meaning a huge number of devices intelligently communicating in the presence of internet protocol that cannot be directly operated by human beings but exist as components in buildings, vehicles or the environment. According to the Internet Engineering Task Force (IETF) organization’s definition, IoT is the networking of smart objects in which smart objects have some constraints such as limited bandwidth, power, and processing accessibility for achieving interoperability among smart objects.  Chapter-5 Internet of things (IoT) According to the IEEE Communications category magazine’s definition, IoT is a framework of all things that have a representation in the presence of the internet in such a way that new applications and services enable the interaction in the physical and virtual world in the form of Machine-to- Machine (M2M) communication in the cloud. According to the Oxford dictionary’s definition, IoT is the interaction of everyday object’s computing devices through the Internet that enables the sending and receiving of useful data  Chapter-5 Internet of things (IoT) IoT refers to the set of devices and systems that interconnect real-world sensors and actuators to the Internet. This includes many different systems.  Chapter-5 Internet of things (IoT)  Chapter-5 Internet of things (IoT)  Chapter-5 Internet of things (IoT) offers a number of benefits to organizations, enabling them to: ▪ Monitor their overall business processes; ▪ Improve the customer experience; ▪ Save time and money; ▪ Enhance employee productivity; ▪ Integrate and adapt business models; ▪ Make better business decisions; and ▪ Generate more revenue Sensors and Actuators Sensors and actuators are the fundamental building blocks of modern technology, enabling devices to interact with the physical world. Sensors collect data from the environment, while actuators convert digital signals into physical actions, powering a wide range of applications. by Abebaw Agegn preencoded.png Sensor Types and Characteristics Temperature Sensors Proximity Sensors Pressure Sensors Measure ambient heat and Detect the presence and Measure the force or weight provide crucial data for climate distance of objects, enabling applied to a surface, crucial for control, safety monitoring, and applications like automated applications like tire pressure process optimization. doors, robotics, and security monitoring and industrial systems. process control. preencoded.png Actuator Types and Characteristics Electric Motors Solenoids Convert electrical energy into rotational motion, Produce linear motion through the use of an powering a wide range of devices from household electromagnetically induced magnetic field, common appliances to industrial machinery. in valves, locks, and switches. Hydraulic Actuators Piezoelectric Actuators Utilize the power of pressurized fluid to generate large Respond to electrical signals by expanding or forces and precise movements, ideal for heavy-duty contracting, enabling precise and fast-acting control in applications. devices like inkjet printers. preencoded.png Sensor-Actuator Integration 1 Sensing Sensors collect data from the environment, measuring physical quantities like temperature, pressure, or movement. 2 Processing A controller or microprocessor receives the sensor data and determines the appropriate response. 3 Actuation Actuators convert the electronic signals from the controller into physical actions that affect the environment. preencoded.png Resource Reservation, Traffic Shaping, and Policing 1 Resource Reservation 2 Traffic Shaping Ensuring availability of Controlling the rate, critical resources like volume, and timing of bandwidth, storage, and data flow to optimize processing power to network performance guarantee Quality of and prevent congestion. Service. 3 Traffic Policing Enforcing policies to monitor and limit network traffic to maintain service-level agreements and security protocols. preencoded.png Scheduling Mechanisms and QoS Models Real-Time Scheduling Ensuring critical tasks are executed within strict time constraints to meet performance and safety requirements. QoS Models Defining service-level objectives and metrics to prioritize and differentiate network traffic based on application needs. Dynamic Adaptation Adjusting resource allocation and scheduling in response to changing conditions to maintain optimal performance. preencoded.png Challenges and Future Trends Scalability Real-Time Responsiveness Energy Efficiency Handling the exponential Ensuring critical applications Optimizing power consumption growth in the number of can react instantaneously to of sensor networks and connected devices and the changes in the physical world. actuators to enable long-term, volume of data generated. sustainable deployments. preencoded.png Sensor and Actuators: Powering Intelligent Systems Sensors and actuators are the building blocks of smart, interconnected devices, enabling data collection and dynamic control. by Abebaw Agegn preencoded.png Sensor Types and Characteristics Diverse Sensors Smart Sensing Accuracy Matters Temperature, pressure, light, Advanced sensors integrate Sensor precision and reliability motion - sensors monitor a wide processing capabilities for on- are critical for robust system range of environmental device analytics and decision- performance. conditions. making. preencoded.png Actuator Types and Characteristics Motors Solenoids Provide mechanical motion Translate electrical signals and force for control into linear or rotational systems. motion. Valves Servos Regulate the flow of liquids Precise angular position and gases in industrial control for robotics and applications. automation. preencoded.png Sensor-Actuator Integration 1 Sensing Collect data on environmental conditions and system state. 2 Processing Analyze sensor data to determine appropriate control actions. 3 Actuation Execute control commands to modify system behavior. preencoded.png Resource Reservation and Traffic Control Resource Reservation Traffic Shaping Ensure reliable resource Regulate data flow to allocation for mission- optimize network critical applications. performance and utilization. Traffic Policing Enforce policies to prevent network congestion and abuse. preencoded.png Scheduling and Quality of Service Prioritization Schedule mission-critical tasks and data to meet deadlines. Bandwidth Allocation Assign network resources based on application requirements. Latency Control Minimize delays for time-sensitive applications and services. preencoded.png Challenges and Future Trends 1 Scalability 2 Energy Efficiency Accommodate growing Optimize power numbers of connected consumption for devices and data. battery-operated sensor networks. 3 Autonomous 4 Interoperability Control Ensure seamless Leverage AI and integration across machine learning for heterogeneous systems self-healing and and platforms. adaptation. preencoded.png  Chapter-5 THEND