Top 18 Embedded Systems Interview Questions & Answers


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. Interrupt architecture allows the use of interrupt by the processor whenever an Input/output is ready for the processing.

Whereas, Software design structure can be changed dynamically and re-usability features, used to define the components. It also includes easy creation, modification and removal of the components from the software. Examples could be the use of virtual drivers in case of Network simulators,also the support of virtual device drivers in case a user runs an additional OS in a virtual box kind of a software.

The thread uses the signaling concept that allows the initialization to be done using the semaphore that keeps the states updated and handle the interrupt in an easy way. The input/output device getting the request and it also passes the semaphore to handle. The thread is having the minimum latency that uses the first level interrupt handler to handle the interrupts completely. It allows the priority of the thread to be set and it doesn’t allow the context to be change as well.

It allows large virtual memory to be provided when only a smaller physical memory is available. Static keyword can be used with variables as well as functions. A variable declared static will be of static storage class and within a function, it maintains its value between calls to that function. A variable declared as static within a file, scope of that variable will be within that file, but it can’t be accessed by other files. In this scheme, the hardware reads its IO from predefined memory addresses instead of over a special bus.

Null pointer actually means a pointer that does not point to any valid location. We define a pointer to be null when we want to make sure that the pointer does not point to any valid location and not to use that pointer to change anything. If we don’t use null pointer, then we can’t verify whether this pointer points to any valid location or not.

Top 18 Embedded Systems Interview Questions

Analytical model allows the components to deal with the concurrency that are given during the process and the quantitative constraints that might come in between the components. Whereas, computational model deal with the non-deterministic abstraction hierarchy that has computational complexity to deal with the concurrency and allow it put also the physical constraints. Hardware design is designed with the collaboration of interconnected parallel components that inherits the properties of each other. Whereas, Software design is designed with sequential components, that are based on objects and threads. Mutex can be allocated to another mutex that is running some task at a particular time and allow the kernel to have synchronization in between them.

Whereas, Computational model can, deal with constraints easily and it provides an upgradeable solution. All interrupts are enabled during execution of the bottom half. The top half saves the device data into the specific buffer, schedules bottom half and exits. This way the top half can service a new interrupt while the bottom half is working on the previous.

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. Embedded systems require infinite loops for repeatedly processing or monitoring the state of the program.

Top 18 Embedded Systems Interview Questions & Answers

Obviously, the compiler won’t be able to inline a recursive function infinitely. It may not inline it at all or it may inline it, just a few levels deep. Semaphore object basically acts as a counter to monitor the number of threads accessing a resource. Here the use of registers is optimised as most of the memory access operations are limited to store and load operations. Analytical model is the equation based model that doesn’t have the time-sharing and parallelism concepts. Whereas, time-sharing and parallelism is used, in the abstract method that provides the theories of complexity and the real time evaluation.

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DMA stands for Direct Memory Access controller that handles the allocation of the memory dynamically to the components and allows the data to be transferred between the devices. It is used for the communication between different input/output devices. It automatically detects the devices that are present for the transfer of data between the input/output devices. The interrupt can be used to complete the data transfer between the devices.

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In this scheme, the operating system retrieves data from secondary storage in same-size blocks called pages. The paging scheme allows the physical address space of a process to be non continuous. Paging allows OS to use secondary storage https://globalcloudteam.com/ for data that does not fit entirely into physical memory. Interrupt latency is a time taken to return from the interrupt service routine post handling a specific interrupt. By writing minor ISR routines, interrupt latency can be reduced.

The processor in this case calls a special function to handle the request that comes and leave all the work that is getting performed at that time. The special function that is known as interrupt handler or the interrupt service routine consists of all the input, and output queries, or the interrupts handled by it. There are properties of starvation that can creep in when handling the input/output requests. The data can be lost if the interrupt doesn’t get handled before the time runs out. This is a technique that is use to deal with the short processes that involve input and output.

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This means you’ll have simpler software, but it also means main memory will get more access requests. The const keyword make sure that the value of the variable declared as const can’t be changed. So, the use of const with volatile keyword makes perfect sense. Hardware design focuses on individual components that are represented using analytical model that uses the transfer functions. Whereas, Software design represent the components using computation model that can have abstract execution engine or it can use the virtual machine that are non-deterministic. Paging is a memory management scheme by which computers can store and retrieve data from the secondary memory storage when needed in to primary memory.

Interrupt latency can be reduced by writing minor ISR routines. But doing so, the result will be having a private copy of that variable in each source file which includes the header file. So it will be wise not to declare a static variable in header file, unless you are dealing with a different scenario.

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For instance, the case of a program state continuously being verified for any exceptional errors that might just happen during run-time such as memory outage or divide by zero, etc. The C’s volatile keyword is a qualifier that tells the compiler not to optimize when applied to a variable. By declaring a variable volatile, we can tell the compiler that the value of the variable may change any moment from outside of the scope of the program.

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But you have to make sure that you are not including the same file twice. There is no limit to how many header files that can be included. But the number can be compiler dependent, since including multiple header files may cause your computer to run out of stack memory. According to the instruction sets used, computers are normally classified into RISC and CISC.

Reason behind this is that at loop termination, comparison to zero can be optimized by the compiler. So they don’t need to load the loop variable and the maximum value, subtract them and then compare to zero. embedded system meaning It is used to reset to the original state whenever some inappropriate events take place such as too many commands being given at the same time or other activities that result in malfunctioning of the GUI.

Hence to avoid the input/output units from getting overloaded with requests, we use multibyte buffers. An ISR is an interrupt handler, a callback subroutine which is called when a interrupt is encountered. A semaphore S is basically an integer variable that apart from initialization is accesses only through atomic operations such as wait() and signal(). Analytical models can’t deal with the partial and incremental specifications that are non-deterministic. It is also not good in controlling the computation complexity that is used in the hardware design.

Multi-threading provide lot of functionality to the system to allow more than one task can be run at a time. But, if there any problem comes in any program or the process than the entire system comes to a halt and slows down the whole system. To control the behavior of this the preemptive multi-threading is used.

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It’s normally the case that some devices transfer the output either in a bursty or a sequential manner and also during input entry. If we take the example of keyboards, all the data entered is stored in a buffer and given at a time or one character at a time. RISC could carry out a few sets of simple instructions simultaneously. Fewer transistors are used to manufacture RISC, which makes RISC cheaper. RISC has uniform instruction set and those instructions are also fewer in number. Due to the less number of instructions as well as instructions being simple, the RISC computers are faster.

The embedded system should have a function that can allow the fixing the system if anything goes wrong with it. Watchdog timer is a tool that is used in embedded system and having a long-fuse that runs several seconds. Watchdog require the user to put some value before it runs out of time and reset the whole process as this can harm the data and the system.

It is used to give the high quality performance as, the input/output device can perform the operations that are in parallel with the code that are in execution phase. It consists of 8-bit microcontrollers that are used to control the overall system in execution. The interrupts that comes in between the input/output operations gets detected when the input/output devices are ready. The interrupt never gets handled directly rather, it sends the interrupt signal to the thread to the input/output device that is ready to allow the thread to take necessary actions.

An ISR returns nothing because there is no caller in the code to read the returned values. Enter the email address you signed up with and we’ll email you a reset link. Suppose you have a chess board how many boxes will be there then you have to find no boxes of type 2×2, 3×3, 4×4, 5×5, 6×6, and 7×7 (question-answer/aptitude). Explain binary search time complexity in every case (this wasn’t the exact question but related to this). So I went through the Qualcomm interview which is pretty good and had a great conversation with the interviewer, and I’m going to share every possible aspect of mine.

External signals, some condition in the program or by the occurrence of some event, these could be the reasons for generation of an interrupt. In case of interactive systems display of menu list and reading in the choices of user’s could be encapsulated as a single unit. CISC again have their own advantages and they are preferred whenever the performance and compiler simplification are the issues to be taken care of.

Resetting by WDT can be done when the process is half complete. Watchdog timer have the counter that is used to watch the processes that are running and if there is any issue occurs then WDT itself times out. The resetting of the system will be done to always give it the best possible way to execute the process.

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