30+ Firmware Engineer Interview Questions and Answers

List of DSA questions including merge sort, tree mirror check, rotated sorted array search, linked list palindrome and loop detection and removal.

• Merge sort is a divide and conquer algorithm that sorts an array in O(nlogn) time complexity.

• To check if two trees are mirror, we need to compare their left and right subtrees recursively.

• To find an element in a rotated sorted array, we can use binary search algorithm.

• To check if a linked list is palindrome, we can use stack or recu...read more

Structure padding is the insertion of unused bytes between members of a structure to align the data in memory.

• Padding is added to ensure that each member of the structure is aligned to a memory address that is a multiple of its size.

• Padding can be compiler-dependent and can vary based on the target architecture.

• Padding can affect the size of the structure and the performance of the program.

• Example: struct MyStruct { char a; int b; char c; }; - padding will be added between a ...read more

Design FSM to generate square waves at 1KHz and 2KHz on ports P1 and P2, optimize prime number code.

• Implement a Finite State Machine (FSM) to generate square waves at 1KHz and 2KHz on ports P1 and P2.

• Use counters and timers to control the frequency of the square waves.

• Optimize the prime number code by using algorithms like Sieve of Eratosthenes or trial division.

Implement traffic signal using C and Pascal's triangle.

• For traffic signal, use a state machine to switch between red, yellow, and green lights.

• For Pascal's triangle, use nested loops to calculate and print the triangle.

• Ensure proper timing and synchronization for the traffic signal.

• Use appropriate data structures and algorithms for efficient implementation.

The program prints integers in an array that are repeated thrice.

• Iterate through the array and count the occurrences of each integer.

• Print the integers that have a count of three.

Use bitwise operations to swap the bytes of the integer without using a second variable.

• Use bitwise AND and bitwise OR operations to swap the bytes of the integer.

• Shift the bytes to the correct positions using bitwise operations.

• Example: a = 0xabcd; a = ((a & 0x00FF) << 8) | ((a & 0xFF00) >> 8);

Pull-up resistors in I2C are used to ensure proper communication by providing a defined voltage level when the bus is in an idle state.

• Pull-up resistors are used to pull the signal high when no device is actively driving it low.

• They prevent floating bus conditions and help in maintaining signal integrity.

• Pull-up resistors are typically connected to the SDA and SCL lines in an I2C bus.

• Common values for pull-up resistors in I2C are around 2.2kΩ to 10kΩ.

• Without pull-up resistors...read more

This program reverses a given string in C language.

• Declare a character array to store the input string.

• Find the length of the string using the strlen() function.

• Initialize two variables, one pointing to the start of the string and the other pointing to the end.

• Swap the characters at the start and end positions using a temporary variable.

• Increment the start pointer and decrement the end pointer until they meet in the middle.

• Print the reversed string.

Communication protocols are sets of rules that govern the exchange of data between devices.

• Some common communication protocols include UART, SPI, I2C, CAN, Ethernet, and USB.

• Each protocol has its own advantages and disadvantages, and is suited for different types of applications.

• For example, UART is a simple protocol commonly used for serial communication between microcontrollers and sensors, while Ethernet is a more complex protocol used for networking.

• Understanding differen...read more

Code bloating refers to the unnecessary increase in the size of software code due to redundant or inefficient programming practices.

• Code bloating can occur when developers use inefficient algorithms or write redundant code.

• It can also happen when unnecessary features or libraries are included in the codebase.

• Code bloating can lead to slower performance, increased memory usage, and longer development times.

• Examples of code bloating include using nested loops when a single loop...read more

a++ is faster than a=a+1 because it is a single operation compared to two operations in a=a+1.

• a++ is a single operation that increments the value of a directly

• a=a+1 involves two operations - addition and assignment

• Example: int a = 5; int b = a++; // b will be 5, a will be 6

• Example: int a = 5; int b = a=a+1; // b will be 6, a will be 6

BJT and MOSFET are models used to represent transistors in electronic circuits.

• BJT stands for Bipolar Junction Transistor and has three regions: emitter, base, and collector.

• MOSFET stands for Metal Oxide Semiconductor Field Effect Transistor and has three terminals: source, gate, and drain.

• BJT is a current-controlled device while MOSFET is a voltage-controlled device.

• BJT has a low input impedance while MOSFET has a high input impedance.

• BJT is used in low power applications wh...read more

map and unordered_map are associative containers while vector and list are sequence containers.

• map and unordered_map are used to store key-value pairs while vector and list are used to store sequences of elements.

• map and unordered_map provide faster search and insertion of elements while vector and list provide faster insertion and deletion of elements.

• map and unordered_map use red-black trees and hash tables respectively while vector and list use arrays and linked lists resp...read more

Volatile keyword in C is used to indicate that a variable may be changed unexpectedly by external factors.

• Volatile keyword tells the compiler not to optimize the variable because it can be changed by external factors.

• Commonly used for memory-mapped hardware registers or variables accessed by multiple threads.

• Example: volatile int *ptr = (int *)0x1234; // pointer to a memory-mapped hardware register

Fibonacci series is a sequence of numbers where each number is the sum of the two preceding ones.

• Declare variables for first, second and next numbers

• Initialize first and second numbers as 0 and 1 respectively

• Loop through the desired number of terms and calculate the next number as the sum of the previous two

• Store the result in an array

• Return the array

HDD stands for Hard Disk Drive, a data storage device used in computers to store and retrieve digital information.

• HDDs use magnetic storage to store data on spinning disks called platters.

• They have read/write heads that move across the platters to access and modify data.

• HDDs are typically used for long-term storage of large amounts of data in desktops, laptops, servers, and other devices.

• Examples of HDD manufacturers include Seagate, Western Digital, and Toshiba.

Synchronizing thread blocks is important for efficient and correct execution of parallel programs.

• Thread blocks must be synchronized to avoid race conditions and ensure correct program output.

• Synchronization can be achieved using locks, semaphores, or barriers.

• Examples of synchronization include ensuring that shared resources are accessed by only one thread at a time, or that threads wait for each other before proceeding.

• Synchronization can also be used to optimize program pe...read more

To check stack overflow, monitor stack usage and compare it to the maximum stack size.

• Monitor stack usage by keeping track of the current stack pointer.

• Compare the current stack pointer to the start of the stack and the maximum stack size.

• Use a watchdog timer to detect stack overflow if the stack pointer exceeds the maximum stack size.

• Use a stack overflow handler to gracefully handle stack overflow and prevent system crashes.

Designing a path for a plane involves considering factors like altitude, speed, weather conditions, and air traffic.

• Consider the altitude and speed requirements for the flight

• Take into account weather conditions and potential turbulence

• Plan the route to avoid congested airspaces and potential conflicts with other aircraft

• Use navigation systems and communication with air traffic control to ensure a safe and efficient path

Dynamic polymorphism is the ability of an object to take on multiple forms during runtime.

• It allows objects of different classes to be treated as if they are of the same class.

• It is achieved through virtual functions and inheritance.

• Examples include function overriding and templates in C++.

C++ has four types of casts: static_cast, dynamic_cast, const_cast, and reinterpret_cast.

• static_cast is used for implicit conversions between related types

• dynamic_cast is used for runtime type checking and casting of polymorphic types

• const_cast is used to remove const or volatile qualifiers from a variable

• reinterpret_cast is used for low-level casting between unrelated types

• Examples: static_cast(3.14), dynamic_cast(basePtr), const_cast(str), reinterpret_cast(&ptr)

Micron is a global leader in memory and storage solutions, providing innovative products for a wide range of applications.

• Micron manufactures memory and storage products such as DRAM, NAND, and SSDs.

• They cater to various industries including data centers, automotive, consumer electronics, and more.

• Micron focuses on developing cutting-edge technologies to meet the growing demands of the digital world.

A counter can be created using D flip-flops by connecting the output of one flip-flop to the input of the next.

• Connect the Q output of one D flip-flop to the D input of the next flip-flop

• Use clock signal to trigger the flip-flops and increment the count

• Use additional logic gates if needed for specific counter functionality

Functors are objects that can be treated as functions in C++. They are used for generic programming and can be passed as arguments.

• Functors are often used in algorithms that require a function object as a parameter.

• They can be used to implement callbacks and event handlers.

• Functors can be used to create custom comparators for sorting algorithms.

• They can also be used to implement function objects for mathematical operations.

• Examples of functors in C++ include std::function, st...read more

IPC mechanisms in Linux are used for inter-process communication between processes running on the same system.

• IPC mechanisms include pipes, message queues, shared memory, and semaphores.

• Pipes are used for one-way communication between two processes.

• Message queues allow for asynchronous communication between processes.

• Shared memory allows multiple processes to access the same memory space.

• Semaphores are used for synchronization between processes.

• IPC mechanisms can be accessed ...read more

Storage classes in C specify the lifetime and visibility of variables.

• auto: default storage class for local variables

• register: stores variables in CPU registers for faster access

• static: retains value between function calls

• extern: used to declare variables that are defined in another file

• typedef: creates a new name for an existing data type

Coding threads with RTOS involves creating and managing multiple threads in real-time operating systems.

• Understand the RTOS scheduling algorithm to prioritize threads.

• Use synchronization mechanisms like semaphores and mutexes to avoid race conditions.

• Implement thread-safe data structures to share data between threads.

• Consider the stack size and priority of each thread to prevent stack overflow and ensure timely execution.

I have always been fascinated by the intersection of hardware and software, and enjoy the challenge of working on low-level programming.

• Passion for working on embedded systems

• Interest in developing efficient and reliable firmware

• Enjoy problem-solving and debugging at a low level

• Excitement for working on cutting-edge technology

• Desire to work in a dynamic and fast-paced environment

The question asks to predict the output of C programs.

• Understand the logic and flow of the program.

• Consider the input values and how they affect the output.

• Check for any conditional statements or loops that may alter the output.

• Compile and run the program to verify the output.

Implementing memcpy function in C programming language

• Use a loop to copy each byte from source to destination

• Ensure to handle overlapping memory regions correctly

• Consider using pointer arithmetic for efficient copying

A C program to swap elements in an array of strings

• Use a temporary variable to swap elements in the array

• Iterate through the array and swap elements at each index

Experience with MQTT protocol for communication in IoT devices.

• Developed firmware using MQTT protocol for real-time communication

• Implemented MQTT client libraries in embedded systems

• Worked on MQTT topics, QoS levels, and message retention policies

Controllers are devices that manage the operation of other devices or systems.

• Controllers receive input, process it, and send output signals to control the operation of other devices.

• Examples of controllers include microcontrollers, PLCs (Programmable Logic Controllers), and PID controllers.

• Controllers can be used in various applications such as industrial automation, robotics, and consumer electronics.

Interrupts are signals sent to the CPU to temporarily suspend the current program and execute a specific task.

• Interrupts allow the CPU to handle external events without constantly checking for them.

• There are different types of interrupts such as hardware interrupts and software interrupts.

• Examples of interrupts include keyboard input, timer expiration, and hardware errors.

A linked list is a linear data structure where each element is a separate object called a node.

• Nodes contain data and a reference to the next node in the sequence.

• Linked lists can be singly linked (each node points to the next) or doubly linked (each node points to both the next and previous).

• Example: Node 1 -> Node 2 -> Node 3 -> null