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mbedded Systems

Embedded Systems

Everything about embedded systems
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So-called embedded systems are, as the name suggests, systems that are embedded in a larger technical context. These are binary-valued digital systems, which in common parlance are usually referred to as computer or computing systems.

The embedded system interacts with the higher-level system. And this usually takes one of these two forms: In the first case, the computer is responsible for classic monitoring, control or regulation functions. In the second case, the embedded system processes signals or data, for example in encoding, decoding, encrypting, decrypting or filtering. This is often referred to as a computer unit or the control unit.

 

What are embedded systems and where are they used?

As already mentioned, an embedded system is always part of a larger system. By the way: If a system separates various functions into several embedded systems, this is called a self-contained system. For this higher-level system, an embedded system usually takes over important functions in order to maintain operation. This process takes place permanently and virtually everywhere in our modern everyday lives: Whether in ultrasonic devices, i.e. medical technology, in white goods such as refrigerators, in all automotive manifestations from cars to trucks and other vehicles, or of course within electrical engineering, where the IT infrastructure is one of the main areas of application - in all machines and devices, an embedded system works in the background. In these cases, the embedded systems always have a special task; after all, they were developed specifically for this purpose. A simple example of this is to switch the host device on and off, to send devices or messages to other systems when clearly defined events occur. It goes without saying that the software must be precisely adapted to the respective function.

 

Embedded Systems – Hardware and Software

The just mentioned adaptation of the software to the respective task is the rule. For this, the embedded system engineer most often uses an optimized, mixed hardware-software implementation, primarily for cost reasons. This is because it combines the high flexibility of the software with powerful hardware. The software takes over control and interaction tasks via specific interfaces and protocols such as CAN bus, ZigBee, Ethernet or LIN bus. Roughly speaking, the following applies to the hardware: An embedded system usually has only one or only a few microprocessors. The performance is accordingly limited and is usually only sufficient for pure hardware operation. Smaller embedded systems also usually operate without their own operating system. This means that they are dependent on the operating system of the higher-level system. RAFI embedded control units with embedded Linux tend to be the exception here in terms of performance.

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Structure and components of embedded systems

The logical structure of embedded systems is often very similar. Normally there are five components: the control unit, actuators and sensors, the user interface, the environment and the user. The control unit is the central element of embedded systems and their components. This is the main focus of embedded system engineering. However, the opposite is true for the implementation of the system in terms of self-similarity. Especially with regard to the hardware, the external circumstances and possible interference factors define the final result. Possible disturbance factors for the hardware and software systems are: Temperature (heat and cold), humidity and splash water, dust, vibrations, shocks, foreign bodies, electromagnetism or radiation.

 

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Definition of different embedded systems

As already explained, embedded systems can be realized in different forms. We have compiled a few criteria here that can be used to distinguish an embedded system from others.

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Memoryless and dynamic systems

Systems receive input signals and assign output signals to them. If this output signal depends only on the value of the input signal, the embedded system is a so-called memoryless system. However, if input signals from the past also play a role, this is referred to as a dynamic system.

Reactive and interactive systems

Here the name says it all. The system reacts to input events and delivers corresponding output events in response - often within a certain time frame (for example, a beverage dispenser). If the system can be changed by the user, it is called an interactive system (computer).

Hybrid systems

In this type of system, value-continuous stimuli are processed in addition to analog stimuli. In addition, interaction can occur over continuous periods of time or at discrete points in time. 

Monolithic and distributed systems

In the case of a distributed system, the individual system components are either logically or spatially distributed. This means that functionality must be ensured with the help of coupling or networking. Networking or coupling must function smoothly, especially when the time window is minimal, for example in real-time operation. The monolithic system, on the other hand, is logically and spatially structured in one place.

Safety-critical and non-safety-critical systems

This distinction is easy to remember: if safety-critical embedded systems fail, a threat to the system itself, facilities or people occurs. This is not the case with non-safety-critical systems.

Electronic Control Units

In the physical implementation of embedded systems, we speak of Electronic Control Units - the control unit of mechatronic systems. Incidentally, a mechatronic system is one in which the electronics required to control and regulate the mechanics are closely linked to these mechanics.

 

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Embedded System Design

Finally, we would like to turn our attention to design, which in the field of embedded systems is primarily concerned with the relationship between environmental events and the embedded system. Thereby, two different methods are preferably applied - time-driven design and event-driven design. We will now turn our attention to these two variants.

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Time-controlled design

In this case, the system calls up whether events are present at certain intervals - for example, with the help of a timer. This is based on the assumption that events occur at regular intervals. If such an event occurs, the system starts the corresponding reaction. Such a system is real-time capable if the time intervals between the event queries can hardly be measured.

Event-driven design

In the event-driven design of an embedded system, only a previously defined event triggers the likewise previously defined reaction. There are no query routines as in the time-controlled design.

In addition to these two methods of system design, the focus is currently on various methods of regulating the energy requirements of software components.

Software design with regard to the energy requirement

Within the energy-focused software design, independently whether in C code or other programming languages, the following three methods are mainly used:

Minimum runtime

Here it is paid attention to the fact that the actual run time of the program is as small as possible. In addition, the operating state immediately jumps into a kind of stand-by mode when the processor is not working. This can greatly reduce energy consumption.

Uniform design

The program is designed in such a way that the idle times of the processor are as uniform and recurring as possible in the respective time period. In the subsequent step, these idle times are then eradicated with the help of the processor clock frequency. The design thus operates evenly and thus with minimal power dissipation.

Specialized compilers

In addition, specialized compilers can be used to deliver code that is particularly favorable in terms of energy. This results in different energy requirements depending on the instruction, which in turn can be exploited.

 

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Conclusion

Embedded systems are not only diverse in terms of their application, structure and design, but also central to modern life as we know it. If you would like to learn even more about embedded systems, our experts will be happy to help.

 

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