The technical interview is one of the most challenging parts of the hiring process. Embedded Systems Interview Questions and Answers are presented here so that you can review them and be better prepared for your interview.
An embedded system combines hardware and software to perform particular computing functions. It is extensively utilised in many industries and is expected to increase significantly due to computing and artificial intelligence advances.
List of 45 Embedded System Interview Questions and Answers
1. What is an embedded system?
Answer: An embedded system is a specialised computer system designed to perform dedicated functions within a larger mechanical or electrical system. It is typically embedded as part of a complete device and often has real-time computing constraints.
2. What are the key components of an embedded system?
Answer: The key components include:
- Microcontroller/Microprocessor: The core processing unit.
- Memory: ROM (Read-Only Memory) for firmware and RAM (Random-Access Memory) for data storage.
- Peripherals: Input and output interfaces (e.g., GPIO, UART, SPI, I2C) for communication with external devices.
- Operating System: Often a real-time operating system (RTOS) or bare-metal firmware.
3. What is the difference between a microprocessor and a microcontroller?
Answer:
- Microprocessor: Generally refers to a computer system’s CPU (Central Processing Unit). It requires external components (memory, peripherals) to function as a complete system.
- Microcontroller: This type includes the CPU, memory, and peripherals (like GPIO, timers, and ADC) on a single chip. It is designed for specific tasks and does not require external components beyond power and I/O devices.
4. Explain the difference between RAM and ROM in an embedded system.
Answer:
- RAM (Random-Access Memory): Used for temporary data storage during program execution. It is volatile, meaning its contents are lost when power is removed.
- ROM (Read-Only Memory): Used to store firmware and permanent data. It is non-volatile, retaining its contents even when power is off.
5. What is the role of an Interrupt in an embedded system?
Answer: An interrupt is a mechanism by which an external or internal event can alter the sequence of execution of instructions in a microcontroller. It allows the processor to respond promptly to important events, often for handling time-sensitive tasks and asynchronous events.
6. What is polling in the context of embedded systems?
Answer: Polling is a technique used in embedded systems where the processor continuously checks the status of an external device or condition (like a sensor or a flag) in a loop. It is straightforward but inefficient compared to interrupt-driven approaches regarding CPU utilisation and responsiveness.
7. What is a Real-Time Operating System (RTOS)? Give an example.
Answer: A Real-Time Operating System (RTOS) is designed to manage tasks with precise timing requirements. It ensures that critical tasks are executed within strict deadlines. Examples include FreeRTOS, VxWorks, and QNX.
8. Explain the difference between firmware and software.
Answer:
- Firmware: Software embedded into hardware devices (like microcontrollers or peripherals) to control their operation. It is typically stored in ROM.
- Software: General-purpose programs that run on a computer or a device with an operating system, providing user-level functionality.
9. What are watchdog timers, and why are they used in embedded systems?
Answer: Watchdog timers are hardware counters that reset the system if a software or hardware fault occurs and the system fails to respond within a specified time. They help increase the reliability of embedded systems by automatically recovering from faults.
10. Describe the process of debugging an embedded system.
Answer: Debugging an embedded system involves:
- Instrumenting Code: Adding print statements or debug messages.
- Using Debugging Tools: Such as JTAG/SWD debuggers, logic analysers, or oscilloscopes.
- Emulation and Simulation: Running the code on a development board or an emulator to trace and analyse program behaviour.
11. What are some real-time applications of embedded processors?
Answer:
- Passenger vehicles
- The Dishwasher
- Cell phones
- TV
- Medications
12. What operating system is used in embedded systems?
Answer: “Real-time operating systems” are used in embedded systems. 8051 has only 256 bytes of memory and cannot run Windows, Linux, or any similar desktop operating system.
13. Mention the embedded systems used in aerospace.
Answer:
- Control systems for aircraft
- Automated
- In-flight embedded system for passengers
- Controls for engines
14. How many embedded processors are needed to build a modern passenger car?
Answer: A total of 50 processors are installed.
15. Explain the FPGA expansion.
Answer: Field-programmable gate arrays: FPGAs.
16. Is Machine Code a Program?
Answer: Computers only accept machine or ”object code” instructions—computer language rather than programmer language. A programmer’s interpretation of the code is complicated and prone to error. Every piece of software, no matter its format, must be converted into machine code for the computer to execute.
17. What is the maximum oscillator frequency and peak performance of the 8051?
Answer: An 8051’s oscillator frequency could reach 12 MHz, and its peak performance was 1 MIPS.
18. What are real-time embedded systems?
Answer: These systems monitor, respond to, and control environmental conditions in real time. Actuators, sensors, and other input-output interfaces connect this environment to the computer system.
19. Why do embedded systems matter?
Answer: Hardware logic gates, input buffers, timing circuits, output drivers, and so forth can be replaced by an embedded microprocessor.
20. What is a microcontroller?
Answer: As an embedded system, a microcontroller is a self-contained system with peripherals, memory, and a processor.
21. What is the DMA address used for?
Answer: Physical addresses are DMA addresses. During data transfer, a device drives the data and addresses the bus directly. The address is strictly physical.
22. What is interrupt latency? Can it be reduced?
Answer: The interrupt latency is the time it takes to return from an interrupt service routine after handling a specific interrupt. ISR routines can be written to reduce interrupt latency.
23. What is a Watchdog Timer?
Answer: When an electronic system problem occurs, a watchdog timer executes a specific action.
24. What is a semaphore?
Answer: Semaphores control access to the same resource by multiple process threads, such as those in a multiprogramming environment. There are usually two purposes for using semaphores.
25. Define HEXADECIMAL.
Answer: Using this system, large binary numbers can be represented compactly. In embedded systems, it is widely used. Numbers in hex are signified by the prefix ‘0X’ in C (and elsewhere).
26. Describe the memory regions in 8051 devices.
Answer: The 8051 devices have two distinct types of memory. Here they are:
- It is the area of data
- This is the code area.
27. Define the Mask read-only memory.
Answer: Mask programming, or factory-programmed ROM, is not cheap. Memory read-only masks operate at 1.5 times the speed of DRAM.
28. Define the prom.
Answer: Write-once, read-many (WORM) or “once-to-programmable” (OTP) memory.
29. Define the DRAM.
Answer: Information is stored in a small capacitor using read-write memory technology. The capacitor must be periodically refreshed to maintain the required information. The information may be lost if the chip’s power is cut off.
30. Define the SRAM.
Answer: Information is stored using an electronic flip-flop as a read-write memory. Circuits are more complex, but no refreshing is required. Accessing data may take one-third as long as DRAM.
31. State the differences between a mutex and a semaphore.
Answer: The differences between a mutex and a semaphore are listed below in the table:
| MUTEXES | SEMAPHORES |
| It is only released by the acquired thread. | Another thread or process can signal it. |
| Mutexes have a known owner. | The thread owner has yet to be discovered. |
| It provides a deadlock-free mutual exclusion. | It is a synchronisation tool that can overcome that critical section problem. |
| They are binary semaphores. Their states are locked or unlocked. | Semaphores are counterlocks. |
32. What is a recursive function?
Answer: The technique of repeating objects in a self-similar manner is known as recursion. A recursive call of the function occurs when a program permits you to call a function inside another function.
33. What are memory leaks?
Answer: A memory leak is a resource leak that occurs when a computer software poorly controls memory allocations, preventing memory from being freed that is no longer needed. When an item is saved in memory but cannot be accessible by the running code, this is known as a memory leak.
34. What is the automotive embedded system?
Answer: An automotive embedded system is a computer system that can act as a control system for electronic devices affecting the automobile’s mechanism or data.
35. What is an embedded C?
Answer: Embedded C is an extended version of the C programming language. It can be used to develop applications based on microcontrollers, such as device drivers (WiFi device drivers, Camera device drivers, etc.).
36. What causes segmentation fault error in embedded C?
Answer: A segmentation fault error in embedded C is a runtime issue that can occur for various reasons.
- It’s possible that a pointer doesn’t have a proper address or memory location to point to.
- If the user tries to access a read-only memory location.
- If the user tries to release a memory that has already been freed (through a pointer).
37. Why do we use a ‘volatile’ keyword in embedded C?
The volatile keyword prevents the compiler from optimising objects that can change unpredictably. Objects marked as volatile are not optimised because their values can be modified at any time by code outside the scope of the present function.
38. What are Soft and Hard real-time systems?
Answer: A hard real-time system is one in which missing even a single deadline can result in total or catastrophic system failure.
A soft real-time system is one in which one or more failures to reach the deadline are not seen as complete system failures but rather as decreased performance.
39. What are the various levels of testing in an embedded system?
Answer: We have four levels of testing in an embedded system:
- Unit testing.
- Integration testing.
- System testing.
- User acceptance testing.
40. What are the phases of the Software Development Life Cycle?
Answer: The software development life cycle is divided into five stages:
- Customer Requirement: During this phase, the customer fills out a requirement form to write down exactly what they require from the product.
- Analysis: In this phase, the requirements are transformed into documents that include all of the functional requirement specifications.
- Design: During this phase, the product’s design is finalised. The requirements are translated into a design for architecture. The following items are included in this phase:
a.) Design Documentation at the Lowest Level (LLD)
b.) Design Documentation at a High Level (HLD) - Coding: The requirements are transformed into a coded form during this phase.
- Testing: During this phase, the software under development is tested to ensure its high quality. There are two forms of this:
a.) Testing in a static environment
b.) Testing in a dynamic environment - Maintenance: During this phase, the product’s maintenance is carried out.
41. What is software quality assurance?
Answer: Software testing and quality assurance refer to the software development process:
- Improving and monitoring the process
- Ensuring that procedures and standards are followed
- Ensuring that the problems are found and corrected or rectified.
42. What is equivalence partitioning?
Answer: Equivalence partitioning means designing a test case to detect the error in a group or a class.
43. What are some common testing tools for embedded systems?
Answer: Some common testing tools for embedded systems are:
- QTP (Quick Test Professional)
- LoadRunner
- WinRunner
- Silk Test
- TestDirector
44. How does a combination of functions minimise memory requirements in embedded systems?
Answer: The amount of code that needs to be dealt with is decreased, reducing overhead and removing redundancy if the functions have anything in common.
Another feature that is optimised is memory allocation. Grouping a set of related functions as a single unit rather than having them distributed across the programme makes sense.
45. How does using a local variable’s address lead to less-than-optimal code?
Answer: Register allocation is the compiler’s most effective optimisation. It uses the register to manipulate the variable before using memory.
Local variables are often assigned in registers. The compiler won’t assign a local variable to a register if we take its address.
IoT Interview Questions and Answers
Q1. Describe Raspberry Pi
Answer: As a computer, Raspberry Pi can perform all the operations like a conventional computer. Other features include onboard WiFi, GPIO pins, and Bluetooth for external devices.
Q2. Running Raspberry Pi headless – how to?
Answer: SSH can be used to run Raspberry Pi in headless mode. The latest operating system has an inbuilt VNC server for remote desktop access on a Raspberry Pi.
Q3. Stack of IoT protocols
Answer: According to the IoT protocol stack, there are four layers: 1) Sensing and information, 2) Network connectivity, 3) Information processing layer, and 4) Application layer.
Q4. Arduino: Define
Answer: Unlike many other platforms, Arduino uses easy-to-use hardware and software. The microcontroller can read sensor inputs and programmatically control the motors.
Q5. The most common types of sensors in IoT
Answer: IoT sensors mostly use the following types:
- Sensor for smoke
- Thermometers
- Sensor for pressure
- Sensors that detect movement
- Sensor for gas
- Sensors that measure proximity
- Sensors for IR
Q6. How does IoT differ from the business of sensors?
Answer: A sensor business doesn’t need to be connected to the Internet. However, the Internet of Things needs a control side to work.
Q7. PWM is what?
Answer: Pulse width modulation is a method of varying the time the signal is high in analogue form. Users can change the percentage of time as well as signal strength.
Q8. Describe how PWM is used in IoT
Answer: PWM can be used in a wide range of IoT applications, such as controlling a DC motor’s speed or motor’s direction, dimming LEDs, etc.
Q9. Low energy Bluetooth – what is it?
Answer: This wireless technology is a Personal Area Network (PAN) based on Bluetooth Low Energy. Short-distance transmission requires less power than long-distance transmission.
Q10. Defining MicroPython
Answer: MicroPython is a fragment of the Python standard library that implements some of it. ModeMCU microcontrollers can be used to optimise it.
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