INTRODUCTION. What is a system? A system is a way of working, organizing or doing one or many tasks according to a fixed plan, program or set of rules. This tutorial has been designed to help the students of electronics learn the basic -to-advanced concepts of Embedded System and Microcontroller. PDF | 5+ minutes read | Embedded systems in robotics are the framework that This document will cover the basics of C/C++ programming.
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The slides contain material from the “Embedded System Design”. Book and Lecture of Peter Marwedel and from the “Hard. Real-Time Computing Systems” Book. First Steps with Embedded Systems is protected by copyrights. All rights Section 4, Programming Fundamentals, includes brief explanations of basic. SYSTEM EXAMPLES. WASHING MACHINE. It is an automatic clothe washing SYSTEM. Parts: Status display panel, Switches & Dials, Motor,. Power supply.
The system must be kept running for safety reasons. Often backups are selected by an operator. Examples include aircraft navigation, reactor control systems, safety-critical chemical factory controls, train signals.
The system will lose large amounts of money when shut down: Telephone switches, factory controls, bridge and elevator controls, funds transfer and market making, automated sales and service. This encapsulation keeps faults from propagating from one subsystem to another, thereby improving reliability.
This may also allow a subsystem to be automatically shut down and restarted on fault detection. Immunity Aware Programming High vs. For low-volume or prototype embedded systems, general purpose computers may be adapted by limiting the programs or by replacing the operating system with a real-time operating system.
Embedded software architectures[ edit ] There are several different types of software architecture in common use. Simple control loop[ edit ] In this design, the software simply has a loop. The loop calls subroutines , each of which manages a part of the hardware or software.
Hence it is called a simple control loop or control loop. Interrupt-controlled system[ edit ] Some embedded systems are predominantly controlled by interrupts.
This means that tasks performed by the system are triggered by different kinds of events; an interrupt could be generated, for example, by a timer in a predefined frequency, or by a serial port controller receiving a byte. These kinds of systems are used if event handlers need low latency, and the event handlers are short and simple. Usually, these kinds of systems run a simple task in a main loop also, but this task is not very sensitive to unexpected delays.
Sometimes the interrupt handler will add longer tasks to a queue structure.
Later, after the interrupt handler has finished, these tasks are executed by the main loop. This method brings the system close to a multitasking kernel with discrete processes. Cooperative multitasking[ edit ] A nonpreemptive multitasking system is very similar to the simple control loop scheme, except that the loop is hidden in an API. The advantages and disadvantages are similar to that of the control loop, except that adding new software is easier, by simply writing a new task, or adding to the queue.
Preemptive multitasking or multi-threading[ edit ] In this type of system, a low-level piece of code switches between tasks or threads based on a timer connected to an interrupt.
This is the level at which the system is generally considered to have an "operating system" kernel. Depending on how much functionality is required, it introduces more or less of the complexities of managing multiple tasks running conceptually in parallel.
As any code can potentially damage the data of another task except in larger systems using an MMU programs must be carefully designed and tested, and access to shared data must be controlled by some synchronization strategy, such as message queues , semaphores or a non-blocking synchronization scheme.
Because of these complexities, it is common for organizations to use a real-time operating system RTOS , allowing the application programmers to concentrate on device functionality rather than operating system services, at least for large systems; smaller systems often cannot afford the overhead associated with a generic real-time system, due to limitations regarding memory size, performance, or battery life. The choice that an RTOS is required brings in its own issues, however, as the selection must be done prior to starting to the application development process.
This timing forces developers to choose the embedded operating system for their device based upon current requirements and so restricts future options to a large extent. These trends are leading to the uptake of embedded middleware in addition to a real-time operating system.
Microkernels and exokernels[ edit ] A microkernel is a logical step up from a real-time OS.
The usual arrangement is that the operating system kernel allocates memory and switches the CPU to different threads of execution. User mode processes implement major functions such as file systems, network interfaces, etc. In general, microkernels succeed when the task switching and intertask communication is fast and fail when they are slow. Exokernels communicate efficiently by normal subroutine calls.
The hardware and all the software in the system are available to and extensible by application programmers.
Monolithic kernels[ edit ] In this case, a relatively large kernel with sophisticated capabilities is adapted to suit an embedded environment. This gives programmers an environment similar to a desktop operating system like Linux or Microsoft Windows , and is therefore very productive for development; on the downside, it requires considerably more hardware resources, is often more expensive, and, because of the complexity of these kernels, can be less predictable and reliable.
Common examples of embedded monolithic kernels are embedded Linux and Windows CE. Despite the increased cost in hardware, this type of embedded system is increasing in popularity, especially on the more powerful embedded devices such as wireless routers and GPS navigation systems. Here are some of the reasons: Ports to common embedded chip sets are available.
It is typically written in a high level format and then compiled down to provide code that can be lodged within a non-volatile memory within the hardware. Embedded systems hardware When using an embedded system there is a choice between the use of a microcontroller or a microprocessor. As they require more devices on the board, but they allow more expansion and selection of exact peripherals, etc, this approach tends to be used for the larger embedded systems.
Whatever type of processor is used in the embedded system, it may be a very general purpose type of one of the many highly specialised processors intended for a particular application.
In some cases custom designed chips may be viable for a particular application if quantities are sufficiently high. One common example of a standard class of dedicated processor is the digital signal processor, DSP. This type of processor is used for processing audio and image files in particular. Processing is required very quickly as they may be used in applications such as mobile phones and the like.
Embedded systems software One of the key elements of any embedded system is the software that is used to run the microcontroller. The code is normally in hex code and provides the basic instructions for each operation of the processor.
This form of code is rarely used for embedded systems these days. It is difficult to understand and debug. To overcome this, high level programming languages are often used.
The code for the embedded system will typically be stored on a form of non-volatile memory held on the processor board. The code is called firmware - the idea is that it is not updated in the same way that software is, being held in the embedded system and it cannot be changed by the user. Often it is possible to update the software, but this can mean changing the memory card on which the firmware is held, or by updating it in another way.
Often additional tools may be used to help with the development of the firmware.