Embedded Programming Interview Questions for Engineering Freshers Basics Tutorials

What are the functional requirements that are used in the embedded systems?

Functional requirements specifies the discrete and the logic to provide the services, functionality, features and the implementation that is independent from the components that are getting used in it. These are used to represent the constraints that are in the form of physical and define the probability to specify the components discretely from each other. The functional requirements are given for the hardware as well that gives more performance and measures the physical resources that are present like clock frequency, latency, etc. Functional requirements allow the system and hardware machines to transfer the functions with the non-deterministic probability.

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Why is Model transformations used in the embedded system?

Model transformations involve multiple models that are used to define different views of a system. It provides different level of granularity that it doesn't use either the top-down approach or the bottom-up approach to implement the basic functionality of the system. It is used to integrate the library components used that involves the iteration of the model that needs to be constructed. It also involves the analysis of the model so that the process can be made automated by using the construction tools. The compilation made the progress by improving the code that is written in high level language and the code generator produce the code that is required for the machine language.


What is interaction semantics used in embedded systems?

Interaction semantics allow the actions to be performed by the system components to allow it to get the global behavior. The interaction can be atomic or non-atomic dependent on the interaction between the components. These components can’t be modified using the interference having the other interactions. Languages that are used, having buffered communication, and other languages, that include multi-threaded languages that use non-atomic interactions. There are two types of interactions that are used:
• Strong synchronization: allow the components to participate together and have strong bonding in between. 
• Weakly synchronizing: are asymmetric that required the communication from both the objects.  


What are the different types of system involved in embedded system?

Embedded systems are used to give the response in real time. So, it consists of the real time systems that allow the correct information to be passed to get the correct responses. For example, it includes of the flight control system that produce the responses in real time and it always the take the values also in real time. If any delay been caused by the system then it deals in the fatal error. The real time system includes the system that provides the response on time with the small delay. Real time systems include of many other system such as:
- Hard Real-Time Systems - these are the systems that server the purpose of having constraints that are hard and it totally depends on the time to provide the response on time. 
- Soft Real-Time Systems - these systems serves the purpose of having few delays in giving up the responses that can tolerate small variations.
- Hybrid Real-Time Systems - these systems includes the properties from both the systems and increases the performance.

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What are the different types of Buses used by the embedded systems?

The buses are used to pass the messages between different components of the system. There are buses existing as:
• Memory Bus: it is related to the processor that is connected to the memory (RAM) using the data bus. This bus includes the collection of wires that are in series and runs parallel to each other to send the data from memory to the processor and vice verse. 
• Multiplexed Address/Data Bus: Multiplex data bus consists of the bus that can read and write in the memory but it decreases the performance due to the time consumed in reading and writing of the data in the memory. 
• De-multiplexed Bus: these consists of two wires in the same bus, where one wire consists of the address that need to be passed and the other one consists of the data that need to be passed from one to another. This is a faster method compared to other. 
• Input/Output bus: it uses the multiplexing techniques to multiplex the same bus input and output signals. This creates the problem of having the deadlock due to slow processing of it.


What is the main function of Multiplexed Address/Data Bus?

The memory bus is used to carry the address and the data from the processor to the memory so that it can be easily accessed by the devices. These buses carry the value of the data that has to be passed for the proper functioning. The use of the technique “Time division multiplexing” is used that allow the reading and writing of the data to be done from the same bus line. This requires lots of time to be given to the bus so that it can complete the read and write operation of the data in the memory. This is very expensive process due to the data transfer technique that is used in between the processor and the memory. This also gives the concept of cache and provides algorithms to solve the problems occurring in read and writes operations.


How does Input/Output bus functions?

Input and output devices or functions allow the user to interact with the external files. Input and output functions are used to transfer the load on the bus. It uses the multiplexes having the input and output signals that remain same. Input and output buses move at the slower rate or speed than the processor speed. This increases the problem of bottleneck or the deadlock due to poor performance. There is a possibility to send more transistors for a layout to be given. These different devices may have very different speeds of communication. When programming IO bus control, make sure to take this into account.
In some systems, memory mapped IO is used. In this scheme, the hardware reads its IO from predefined memory addresses instead of over a special bus. This means you'll have simpler software, but it also means main memory will get more access requests.

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 What is the function of simple thread poll in embedded system?

Simple thread poll allow the ready output to be passed for checking by giving it to the bus that is free and then the output is sent along the thread. The bus can send the output depending on the time that has been given and during the transfer the user won’t be able to perform any other operation. The input is given after finding out the bus is free or not and if it free then a check is made to see that the input exists or not. This thread poll is easy to understand but it is not efficient method to allow the data to be put over the bus manually. The problem of not doing multi-tasking can occur due to doing one task at a time. The method is only be used when input/output occurs at interval that are infrequent.


Why is it better to use multi-threading polling then single threading model?

Multi-threading allows a simple thread to be stored and polled. There is no Input/output function that is applied when it is having the poll. When there is no poll available to spawn it makes the system to sleep for an amount of time till the request for another poll reaches. If there is one process that is running then it divides that process into multiple threads and processes it accordingly. It allows the main thread to process all the request and produce the output by combining all other. Multi-threading allows the main thread not to put off the result or the output that will be generated. It also allow the priority of the thread to be changed by allowing to set the priority of the input/output process. It also has some problems with the polling interval that can make a thread starve for some time if the request isn’t handled properly.