u/Prior-Mud2043

After many requests, I’m posting my prep strategy and interview experience here:

Old post : https://www.reddit.com/r/embedded/s/lBKgmJBEsC

Recently got selected after one of the most mentally exhausting interview processes I’ve been through, and I thought I’d share the full story because the outcome could give hope to others

Background:
- almost 4 years experience in automotive validation/testing
- Mostly worked on Vector stack and application-side testing , no regular coding or low level driver work

The important part:
I seriously prepared for around 60 focused days while working full-time.

Prep included:
- C fundamentals (Neso Academy etc.)
- Basic C++
- ARM Cortex-M basics
- RTOS concepts
- Threads, mutexes, semaphores
- Producer-consumer
- Memory layout / linker / stack / heap
- Embedded systems fundamentals
- DSA basics again from scratch
- Some LeetCode medium problems
- Reverse linked list
- Binary search variants
- Hash maps / LRU attempts
- Bit manipulation
- IPC/scheduling concepts

Sources:

- Neso Academy YT playlist for C fundamentals
- Udemy courses by fastbit academy on ARM cortex and RTOS fundamentals
- ChatGPT for fast learning
- online compilers for coding practice and leetcode medium problems here and there

FYI - I used these sources mostly as a tools for brushing up as i had prior context in these topics from my academic days.

Tip: I created separate chat boxes for each topic in ChatGPT and only a particular chat box for only that topic to avoid mixup and quick reference

Also makes it easier to have an interactive quiz generated by the ChatGPT to test how well I’m learning
Interview process was 5 rounds total.

Interview experience:

Round 1:
Concurrency problem involving ordered thread execution using semaphores (odd/even printing style logic). Needed hints but eventually converged. Questions from current work and some academic projects relevant to their work.

Round 2:
Coding:
- Merge two sorted arrays
- Search in sorted matrix

Onsite round 3:
- C Memory map layout in depth grilling
- C fundamentals grilling
- Linked list reversal
- Basic array and pointer manipulation questions
- Deep questions on my relevant project from masters

Onsite round 4:
- Motivation for job change
- Background discussion over work and academic history
- logistic discussions

Round 5.

Got grilled for ~1.5 hours.

Topics:
- Multithreading on single-core systems
- Scheduling overhead
- Why multithreading helps/hurts
- Thread allocation strategy for image-processing systems
- Core vs virtual thread discussion
- types of semaphores and usages
- Asked to design a small parallel processing system and how the resource allocation should be done( theoretical)
- Detailed questions about my exact work experience and implementation depth

Then coding:

1. Implement memmove
2. Reverse bits of a number with optimization discussion
3. matrix problem involving row/column suffix sums

I misunderstood the matrix question twice under pressure.

Then HR called.

Received the written offer letter just today.

Anyway, posting this because during prep I used to read posts like these myself and assume everyone getting into top companies was already cracked from day one.

A lot of us are figuring it out in real time.

FYI - I used ChatGPT for formatting this post, excuse me if any mistakes are there.

A few days ago I posted here seeking advice for interview prep and i am happy to say that i got the offer from the company.

And i would like to thank the people in this sub for giving their valuable suggestions.

I went through 3 rounds of interview after that and 2 before. Total 5 rounds, the 3rd and 4th were f2f and the rest were virtual, the final round was the toughest as , it was with org head I was expecting kind of a behaviour and team fit round but it was more in depth technical round compared all previous rounds with 45 mins of theory and 45 mins of live coding.

It felt like i didn’t make it as i had struggled at few moments, but i think they did see something beyond the struggle.

My last post: https://www.reddit.com/r/embedded/s/QT4s9FKA77

I recently got a call for an MNC, firmware engineer role, had done with 2 virtual rounds

1st round - C fundamentals key words, multithreading , C memory layout, mutexes semaphores and pseudo code for concurrency using semaphores

2nd round - 2 coding questions involving sorted arrays and sorted matrix search

Which i struggled in both, i was able to explain the logic but the second question coding part i kind of fumbled,

Interviewer told that the approach is in right direction but coding needs refinement

I thought I lost this interview, and a day later i got the feedback call asking me to brush up on coding and fundamentals and show up 10 days later for in person interview

I was coming from automotive testing backgr and have been studying only for the past few months. I still feel like i don’t have a chance due to domain switch,

Any inputs on how to prepare and what areas to focus on for next 10 days?