100+ Embedded Software Engineer Interview Questions and Answers

Program to implement linked list using dynamic memory allocation

• Allocate memory for each node using malloc() function

• Use pointers to link nodes together

• Free memory using free() function to avoid memory leaks

I enjoy developing embedded systems because of the challenge and the opportunity to work with hardware.

• I like the challenge of working with limited resources and optimizing code for performance.

• I enjoy the opportunity to work with hardware and see the direct impact of my software on the physical world.

• Embedded systems are used in a wide range of industries, from automotive to aerospace, providing opportunities for diverse and interesting projects.

• I appreciate the ability to w...read more

Different types of pointers, volatile variable, storage classes, Static and extern keywords, ISR

• Pointers: Null pointer, void pointer, function pointer

• Volatile variable: Used to indicate that a variable may be changed by external factors

• Storage classes: auto, register, static, extern

• Static keyword: Used to declare variables that are only accessible within the same file

• Extern keyword: Used to declare variables that are defined in another file

• ISR: Interrupt Service Routine, a fu...read more

A slave in an embedded system can handle two masters by using a bus arbitration mechanism.

• The slave device can prioritize requests from one master over the other based on a predefined protocol.

• The slave can use a bus arbitration technique such as round-robin or priority-based arbitration to manage access from multiple masters.

• The slave may have separate buffers or registers to store data from each master to prevent data corruption or loss.

• The slave can communicate with both m...read more

A shell program to list the last 3 recently opened files.

• Use the 'ls' command with the '-lt' option to list files in descending order of modification time.

• Pipe the output of 'ls' to 'head' command to get the first 3 lines.

• Use 'awk' command to extract only the file names from the 'ls' output.

Code to reverse a linked list

• Create three pointers: prev, current, next

• Iterate through the linked list, updating pointers accordingly

• Set the next of current to prev, move prev and current pointers forward

• Update the head of the linked list to the last node visited

8051 registers are used for I/O operations and control of the microcontroller.

• 8051 has 4 register banks, each with 8 registers

• Registers are used for arithmetic, logical, and bit manipulation operations

• Special function registers (SFRs) control the microcontroller's peripherals

• Examples of SFRs include P0 for I/O operations and TMOD for timer control

I have worked on various embedded boards including Raspberry Pi, Arduino, and BeagleBone.

• Raspberry Pi

• Arduino

• BeagleBone

You can copy files from one device to another by using file transfer protocols like FTP, SCP, or by physically transferring the files via USB or external storage devices.

• Use FTP (File Transfer Protocol) to transfer files over a network

• Use SCP (Secure Copy Protocol) for secure file transfers

• Physically transfer files by connecting devices via USB or using external storage devices like USB drives or SD cards

OOPs concept in C++ involves encapsulation, inheritance, polymorphism, and abstraction.

• Encapsulation: Bundling data and methods that operate on the data into a single unit (class). Example: class Car { private: int speed; public: void accelerate() { speed += 10; } };

• Inheritance: Allows a class to inherit properties and behavior from another class. Example: class ElectricCar : public Car { public: void chargeBattery() { batteryLevel = 100; } };

• Polymorphism: Ability to present ...read more

Flow chart for a project on implementing a temperature control system

• Start with initializing the system

• Check the current temperature

• If temperature is too high, activate cooling system

• If temperature is too low, activate heating system

• Continue monitoring temperature and adjusting as needed

• End the system when temperature is within desired range

CAN protocol is a communication protocol used in embedded systems for reliable and efficient data transmission.

• CAN protocol stands for Controller Area Network protocol.

• It is a serial communication protocol used for real-time applications.

• CAN protocol uses a differential signaling scheme to transmit data.

• It supports multi-master and multi-slave communication.

• CAN protocol uses message-based communication with a priority-based arbitration scheme.

• It provides error detection and e...read more

A BLDC driver module can be made by designing a circuit that controls the commutation of the BLDC motor based on sensor feedback.

• Design a circuit that includes power transistors to drive the motor phases.

• Implement a control algorithm to determine the commutation sequence based on sensor feedback.

• Use Hall effect sensors or encoder feedback to detect the rotor position.

• Apply PWM signals to the power transistors to control the motor speed and direction.

• Consider safety features l...read more

Structures are used to store different data types under one name, while unions allow different data types to be stored in the same memory location.

• Structures allocate memory for each member separately, while unions share the same memory location for all members.

• Structures are used when all members need to be accessed independently, while unions are used when only one member needs to be accessed at a time.

• Example: struct Person { char name[20]; int age; }; union Data { int num...read more

Use a balance scale to compare groups of stones to find the heavier one.

• Divide the stones into 3 groups of 3, 3, and 2 stones.

• Weigh the 3 groups of 3 stones against each other.

• If one group is heavier, weigh 2 of those stones against each other to find the heaviest one.

• If the groups of 3 stones weigh the same, weigh the remaining 2 stones to find the heaviest one.

Add two elements without using a third variable in C program.

• Use bitwise XOR operation to add two elements without carry

• Store the result in one of the variables

• Example: int a = 5, b = 3; a = a ^ b; b = a ^ b; a = a ^ b; // a=3, b=5

C program to arrange elements in ascending order

• Use bubble sort algorithm to compare adjacent elements and swap if necessary

• Iterate through the array multiple times until no more swaps are needed

• Ensure proper error handling for input validation

• Example: int arr[] = {4, 2, 7, 1, 5};

Software designed to run on embedded systems with limited resources and specific functions.

• Embedded software is tailored to the specific hardware it runs on.

• It is often written in low-level languages like C or assembly.

• It must be efficient and optimized for limited resources like memory and processing power.

• Examples include firmware for a smart thermostat or a car's engine control unit.

Use 2 weighs to find the heavier ball out of 8 (7 identical) on a scale

• Divide the 8 balls into 3 groups: 3 balls, 3 balls, and 2 balls

• Weigh the 2 groups of 3 balls against each other

• If one group is heavier, weigh 2 balls from that group to find the heavier ball

• If both groups of 3 balls weigh the same, weigh the remaining 2 balls to find the heavier one

Contact dictionary can be implemented using hash table for fast lookups with O(1) time complexity.

• Use a hash table to store contacts with keys as names and values as contact information.

• Example: { 'John Doe': '555-1234', 'Jane Smith': '555-5678' }

• Time complexity for searching, inserting, and deleting contacts is O(1) with a hash table.

Storage class in C determines the scope, visibility, and lifetime of variables.

• C has four storage classes: auto, register, static, and extern.

• Auto storage class is the default and is used for local variables.

• Register storage class is used for variables that should be stored in CPU registers for faster access.

• Static storage class is used for variables that retain their values between function calls.

• Extern storage class is used to declare variables that are defined in other fil...read more

A program to find prime numbers

• Start with a loop to iterate through numbers

• Check if each number is divisible by any number less than itself

• If not, add it to a list of prime numbers

Structure is a data type that allows storing different data types in a single variable, while union is a data type that allows storing only one value at a time.

• Structure allows storing multiple data types in a single variable, while union allows storing only one value at a time

• In structure, each member has its own memory location, while in union all members share the same memory location

• Example: struct Person { char name[20]; int age; }; union Data { int num; float value; };

• S...read more

The volatile keyword is used in C/C++ to indicate that a variable may be changed unexpectedly by external factors.

• Used to prevent compiler optimizations that assume the variable's value will not change.

• Commonly used for variables shared between threads or accessed by interrupt service routines.

• Example: volatile int sensorValue; // variable updated by hardware interrupts

Example program for single linked list with insertion and deletion of nodes

• Create a struct for the node with data and a pointer to the next node

• Implement functions for insertion at the beginning, end, and at a specific position

• Implement functions for deletion of a node by value or position

Strengths in problem-solving and teamwork, weakness in time management

• Strength: Strong problem-solving skills - able to analyze complex issues and find effective solutions

• Strength: Excellent teamwork - able to collaborate with others to achieve common goals

• Weakness: Time management - sometimes struggle to prioritize tasks and meet deadlines

Deadlock is a situation in which two or more competing actions are each waiting for the other to finish, preventing any of them from completing.

• Occurs in multitasking environments

• Caused by resource contention

• Can be resolved using techniques like deadlock prevention, deadlock avoidance, and deadlock detection

• Example: Process A holds Resource X and waits for Resource Y, while Process B holds Resource Y and waits for Resource X

Call by value passes a copy of the variable, while call by reference passes the actual variable itself.

• Call by value passes a copy of the variable, so changes made to the parameter inside the function do not affect the original variable.

• Call by reference passes the actual variable itself, so changes made to the parameter inside the function affect the original variable.

• In call by value, the function receives a copy of the variable's value. In call by reference, the function r...read more

A diode is a semiconductor device that allows current to flow in one direction only.

• Diodes are used in rectifiers to convert AC to DC.

• They are used in voltage regulators to maintain a constant voltage.

• Diodes are also used in signal processing, such as in radio frequency detectors.

• Light-emitting diodes (LEDs) are used in displays, indicators, and lighting.

• Zener diodes are used for voltage regulation and protection against voltage spikes.

Macro code to set a bit in embedded software

• Define a macro using bitwise OR operator to set a specific bit in a register

• Example: #define SET_BIT(reg, bit) ((reg) |= (1 << (bit)))

• Call the macro with the register and bit number as arguments

ISR routine is a function that is executed in response to an interrupt signal.

• ISR stands for Interrupt Service Routine

• It is used to handle hardware interrupts

• ISR routines are written in C language

• They are executed when an interrupt signal is received

• ISR routines should be short and efficient

• They should not block other interrupts

• Examples of ISR routines include handling keyboard input or timer interrupts

Embedded C is a subset of the C programming language used for programming embedded systems. The volatile keyword is used to indicate that a variable may change unexpectedly.

• Embedded C is a subset of the C programming language that is optimized for embedded systems.

• It typically has limited resources and requires efficient code execution.

• Embedded C may have specific syntax and libraries tailored for the target hardware.

• The volatile keyword is used to indicate that a variable ma...read more

Enum is used to define a set of named constants while struct is used to define a collection of variables of different data types.

• Enum is used to define a set of named constants, while struct is used to define a collection of variables of different data types.

• Enum values are typically integers, while struct members can be of any data type.

• Enums are used when you have a fixed set of values that won't change, while structs are used to group related variables together.

• Example: en...read more

Different function call methods include pass by value, pass by reference, and pass by pointer.

• Pass by value: Copies the value of the actual parameter into the formal parameter of the function.

• Pass by reference: Passes a reference to the memory location of the actual parameter.

• Pass by pointer: Passes the memory address of the actual parameter.

Moral motivation is driven by personal values and beliefs, while monetary motivation is driven by financial incentives.

• Moral motivation is based on doing what is right or ethical, regardless of financial gain.

• Monetary motivation involves being driven by financial rewards or incentives.

• Some individuals may prioritize moral motivation over monetary motivation, while others may prioritize financial gain.

• Examples: A person may choose to work for a non-profit organization out of a...read more

Program to find factorial of a number

• Use a loop to multiply the number with all the numbers less than it

• Handle the case when the number is 0 or 1 separately

• Use recursion to find factorial of a number

Storage classes in C define the scope and lifetime of variables.

• Storage classes include auto, register, static, extern, and typedef.

• Auto variables are local to the block and have automatic storage duration.

• Register variables are stored in CPU registers for faster access.

• Static variables retain their value between function calls.

• Extern variables are declared outside any function and can be accessed by other files.

• Typedef is used to create new data types.

A pointer is a variable that stores the memory address of another variable.

• Types of pointers include null pointers, void pointers, function pointers, and array pointers.

• Example: int *ptr; // pointer to an integer variable

• Example: char *str = 'hello'; // pointer to a character array

Watchdogs are hardware or software timers that monitor the operation of a system and reset it if it fails to respond within a certain time.

• Watchdogs are used to ensure the reliability and safety of embedded systems.

• They can be implemented as hardware or software timers.

• Watchdogs monitor the system by periodically checking for a response or heartbeat signal.

• If the system fails to respond within a specified time, the watchdog timer triggers a system reset.

• Examples of watchdogs ...read more

Use sorting to find the nth largest number in a jumbled array.

• Sort the array in descending order.

• Access the nth element in the sorted array to find the nth largest number.

Zener diode is used as a voltage regulator and to protect circuits from overvoltage.

• Zener diode maintains a constant voltage across its terminals when reverse biased

• It is used in voltage regulator circuits to provide a stable output voltage

• Zener diodes are also used to protect circuits from overvoltage by shunting excess voltage to ground

• They are commonly used in power supplies, voltage regulators, and surge protectors

Biasing is the process of providing a DC voltage or current to establish a desired operating point for electronic components.

• Biasing is used to ensure that electronic components operate within their specified range.

• It involves setting the appropriate voltage or current levels to achieve the desired performance.

• Biasing is commonly used in transistors, amplifiers, and other electronic circuits.

• There are different types of biasing techniques such as fixed bias, self-bias, and vo...read more

Recursion is a process where a function calls itself until a base condition is met.

• Recursion involves breaking down a problem into smaller subproblems and solving them recursively

• It requires a base case to stop the recursion and prevent infinite looping

• Example: Factorial function - n! = n * (n-1)!, where the function calls itself with n-1 until n=1

I heard about ASML through a job search website.

• Job search website

• Online job board

• Referral from a friend who works at ASML

Debugging with gdb involves setting breakpoints, stepping through code, inspecting variables, and analyzing memory.

• Set breakpoints at specific lines of code using 'break' command

• Step through code using 'next' or 'step' commands

• Inspect variables using 'print' command

• Analyze memory using 'x' command

• Use 'continue' command to resume execution

Static, global, and local variables are different types of variables in programming with different scopes and lifetimes.

• Static variables have a fixed memory location and retain their value between function calls.

• Global variables are accessible throughout the entire program.

• Local variables are only accessible within the block of code where they are declared.

I have extensive experience working with telemetry systems in embedded software development.

• Designed and implemented telemetry systems for monitoring and transmitting data in real-time

• Utilized protocols like MQTT, CoAP, and HTTP for communication between embedded devices and servers

• Integrated sensors and actuators to collect and transmit data for remote monitoring and control

• Worked on optimizing telemetry data transmission for efficiency and reliability

• Experience with telemet...read more