- Embedded system - Wikipedia
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Using this embedded system definition it is possible to understand the various basic characteristics one. Typically they are:. When using an embedded system there is a choice between the use of a microcontroller or a microprocessor. 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. One of the key elements of any embedded system is the software that is used to run the microcontroller. 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.
Both Von Neumann as well as various degrees of Harvard architectures are used. Most architectures come in a large number of different variants and shapes, many of which are also manufactured by several different companies. Numerous microcontrollers have been developed for embedded systems use.
Embedded system - Wikipedia
General-purpose microprocessors are also used in embedded systems, but generally, require more support circuitry than microcontrollers. Sometimes these boards use non-x86 processors. In certain applications, where small size or power efficiency are not primary concerns, the components used may be compatible with those used in general purpose x86 personal computers. Boards such as the VIA EPIA range help to bridge the gap by being PC-compatible but highly integrated, physically smaller or have other attributes making them attractive to embedded engineers.
The advantage of this approach is that low-cost commodity components may be used along with the same software development tools used for general software development. Systems built in this way are still regarded as embedded since they are integrated into larger devices and fulfill a single role.
Examples of devices that may adopt this approach are ATMs and arcade machines , which contain code specific to the application.
When a system-on-a-chip processor is involved, there may be little benefit to having a standardized bus connecting discrete components, and the environment for both hardware and software tools may be very different. One common design style uses a small system module, perhaps the size of a business card, holding high density BGA chips such as an ARM -based system-on-a-chip processor and peripherals, external flash memory for storage, and DRAM for runtime memory.
The module vendor will usually provide boot software and make sure there is a selection of operating systems, usually including Linux and some real time choices. These modules can be manufactured in high volume, by organizations familiar with their specialized testing issues, and combined with much lower volume custom mainboards with application-specific external peripherals. Implementation of embedded systems has advanced so that they can easily be implemented with already-made boards that are based on worldwide accepted platforms.
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These platforms include, but are not limited to, Arduino and Raspberry Pi. A common array for very-high-volume embedded systems is the system on a chip SoC that contains a complete system consisting of multiple processors, multipliers, caches and interfaces on a single chip. Embedded systems talk with the outside world via peripherals , such as:. As with other software, embedded system designers use compilers , assemblers , and debuggers to develop embedded system software. However, they may also use some more specific tools:. As the complexity of embedded systems grows, higher level tools and operating systems are migrating into machinery where it makes sense.
For example, cellphones , personal digital assistants and other consumer computers often need significant software that is purchased or provided by a person other than the manufacturer of the electronics. Embedded systems are commonly found in consumer, cooking, industrial, automotive, medical applications. Household appliances, such as microwave ovens, washing machines and dishwashers, include embedded systems to provide flexibility and efficiency.
Embedded debugging may be performed at different levels, depending on the facilities available. The different metrics that characterize the different forms of embedded debugging are: does it slow down the main application, how close is the debugged system or application to the actual system or application, how expressive are the triggers that can be set for debugging e.
Unless restricted to external debugging, the programmer can typically load and run software through the tools, view the code running in the processor, and start or stop its operation. The view of the code may be as HLL source-code , assembly code or mixture of both. Because an embedded system is often composed of a wide variety of elements, the debugging strategy may vary.
For instance, debugging a software- and microprocessor- centric embedded system is different from debugging an embedded system where most of the processing is performed by peripherals DSP, FPGA, and co-processor. An increasing number of embedded systems today use more than one single processor core. A common problem with multi-core development is the proper synchronization of software execution.
Real-time operating systems RTOS often supports tracing of operating system events. A graphical view is presented by a host PC tool, based on a recording of the system behavior. The trace recording can be performed in software, by the RTOS, or by special tracing hardware. RTOS tracing allows developers to understand timing and performance issues of the software system and gives a good understanding of the high-level system behaviors.
Embedded systems often reside in machines that are expected to run continuously for years without errors, and in some cases recover by themselves if an error occurs. Therefore, the software is usually developed and tested more carefully than that for personal computers, and unreliable mechanical moving parts such as disk drives, switches or buttons are avoided.
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A variety of techniques are used, sometimes in combination, to recover from errors—both software bugs such as memory leaks , and also soft errors in the hardware:. For high volume systems such as portable music players or mobile phones , minimizing cost is usually the primary design consideration. 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. 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. 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.
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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. 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. 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.
5 Steps to Getting Started with Embedded Programing
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. Suppose we have a temperature data logger. And it needs to store the data every one hour. It means we need the data at runtime after the system is started. And it will be permanent. And you can retrieve the data later. In some application, we need to generate some delay. Like for blinking an LED, we need a delay. For making square pulse we need a delay. But there is some issue when we generate the delay from the normal coding style by making any loop running for a particular time.
Definitely, this will give you some delay but the code after this loop remains in waiting for state and delayed. So it is not the best approach to generate the delay. For such kind of application where we need a delay for a specific time interval without affecting the normal code execution, we use timer and counter. By setting some register for timer and counter using the programming we get the desired delay. The amount of delay depends on the system frequency and crystal oscillator. Embedded systems hardware has different types of communication ports to communicate with the other embedded devices.
For sending data from one board to other we can use these serial protocols. But for that, we need to program it. To interact with the embedded systems we need input. The input may be provided by the user or by some sensor. Sometimes some systems need more input or output. These input and output are generally divided into ports like P0, P1, P2 and P3 in microcontrollersr. And for that, we need to refer the datasheet of the manufacturer. Some hardware components are common while designing the embedded systems.
But some are different and depends on the application need.