Western Digital Firmware Developer Interview Questions and Answers

Q1. Write monitor for APB protocol
Ans. 
A monitor for APB protocol is a verification component that checks for protocol compliance in APB transactions.
• Monitor should check for valid address, data, and control signals in APB transactions

• It should detect and report any protocol violations or errors

• Monitor should be able to track the state of the APB bus and ensure proper communication between master and slave devices
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Q2. Design FSM - halway with 2 detectors, accuire amout of pepole in room - only one person can pass halway each time.
Ans. 
Design a finite state machine to count the number of people passing through a hallway with 2 detectors, allowing only one person at a time.
• Create states for each detector and the hallway

• Transition between states based on detector inputs

• Use counters to keep track of the number of people passing through

• Implement logic to prevent multiple people from passing simultaneously
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Q1. Projects related questions
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Q2. C program for array swapping
Ans. 
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
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There were mostly embedded c programming questions, like what will be the output of the given code, what is the error that will occur if this program runs, etc. Lasted about 30 minutes.

Q1. Questions were on communications protocols like I2C, UART, SPI, etc. Working and block diagram of project, operating modes of a transistor.
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Q1. Difference between structure and union
Ans. 
Structure is a collection of different data types under one name, while union is a single memory location that can hold different data types at different times.
• Structure allows each member to have its own memory location, while union shares a single memory location for all members.

• In a structure, all members can be accessed simultaneously, while in a union, only one member can be accessed at a time.

• Example: struct Pers...read more
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Q2. What is structure padding and how to pack a structure
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Structure padding is adding empty bytes to align data in memory. Packing a structure removes padding to save memory.
• Structure padding ensures that data members are aligned to memory boundaries for efficient access

• Padding bytes are added between data members to ensure alignment

• Packing a structure removes padding to save memory but may impact performance

• Example: struct example { char a; int b; } - sizeof(struct example)
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Q3. How to check stack overflow
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To check for stack overflow, monitor stack usage and set a limit to trigger an alert if exceeded.
• Monitor stack usage by tracking the stack pointer and comparing it to the stack size.

• Set a limit for stack usage and trigger an alert if the limit is exceeded.

• Use tools like stack analyzers or profilers to detect stack overflow.

• Implement stack canaries or guard zones to detect stack corruption.
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Q1. Difference between semafore and mutex
Ans. 
A semaphore is a signaling mechanism while a mutex is a locking mechanism used to control access to shared resources in multithreaded environments.
• Semaphore is used to control access to a pool of resources, while mutex is used to control access to a single resource.

• Semaphores can be used to allow multiple threads to access a shared resource simultaneously, while mutex allows only one thread to access the resource at a ...read more
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Q2. How to set the priority of a task
Ans. 
Task priority can be set using priority levels or scheduling algorithms in firmware development.
• Use priority levels to assign importance to tasks

• Higher priority tasks are executed before lower priority tasks

• Implement scheduling algorithms like preemptive scheduling or round-robin scheduling to manage task priorities
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Q1. Why you want to join philips
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Q1. Bit manipulation
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Q2. Volatile keywords in c work in which way
Ans. 
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
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Q1. How do you handle stress
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Q2. How do you achieve work life balance
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Q1. Basic about project
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Q2. C coding question
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Q1. Related embedded systems and manual testing
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