Skip to content
JOBSPOT 360 Career guidance, interview preparation and genuine jobs

Embedded / Hardware Engineer interview questions

Embedded and hardware-adjacent interviews go deep on C, how code runs on real hardware, and debugging with limited visibility. Expect bit manipulation, memory layout, interrupts, RTOS concepts and communication protocols, often asked on paper.

11 questions with answer notes · 4 rounds · By the JOBSPOT 360 team

How the selection process usually works

  1. 1

    Online assessment

    C output-prediction, pointers, bit manipulation and digital electronics MCQs.

  2. 2

    Technical round 1

    C programming, memory, data structures and microcontroller basics.

  3. 3

    Technical round 2

    RTOS, drivers, protocols (I2C, SPI, UART, CAN), computer architecture and your projects.

  4. 4

    Managerial / HR

    Project discussion, team fit and offer.

Rounds vary between companies. Smaller teams often merge the technical and managerial rounds, while larger companies may add an extra technical round.

Skills to brush up on

  • C (pointers, memory, bitwise operations)
  • C++ basics
  • Microcontrollers (ARM Cortex-M, AVR, ESP32)
  • RTOS concepts (FreeRTOS)
  • Communication protocols (UART, I2C, SPI, CAN)
  • Computer architecture and OS internals
  • Linux kernel and device driver basics
  • Debugging with JTAG, oscilloscope and logic analyser

Technical questions

  1. 01 What does the volatile keyword do, and when is it required?

    How to answer: It tells the compiler the value may change outside the program's flow, so it must not cache it. Use it for memory-mapped registers, variables shared with ISRs and multi-threaded flags.

  2. 02 Write code to set, clear, toggle and check a bit, and to count set bits.

    How to answer: Use |=, &= ~ and ^= with a mask 1u << n, and & to test. For counting, Brian Kernighan's n &= n - 1 loop is the classic answer.

  3. 03 Explain the memory layout of a C program.

    How to answer: Text (code), initialised data, BSS, heap growing up and stack growing down. Know where globals, statics, locals and malloc'd memory live.

  4. 04 What should and should not be done inside an interrupt service routine?

    How to answer: Keep ISRs short: clear the flag, record data and signal a task. Avoid blocking calls, heavy printing and dynamic memory allocation.

  5. 05 What is the difference between a mutex and a semaphore, and what is priority inversion?

    How to answer: A mutex has ownership and is used for mutual exclusion; a semaphore is for signalling or counting. In priority inversion, a low-priority task holding a lock blocks a high-priority one. It is fixed with priority inheritance.

  6. 06 Compare I2C, SPI and UART.

    How to answer: I2C uses two wires with addressing and supports multiple devices, but is slower. SPI is fast and full duplex, with a chip select per device. UART is asynchronous point-to-point with no clock line.

  7. 07 What is endianness? How would you detect it in code?

    How to answer: It is the byte order in memory. Store 1 in an int and inspect its first byte through a char* pointer.

  8. 08 What is a watchdog timer and why use it?

    How to answer: A hardware timer that resets the system if the software stops "kicking" it, so the device recovers from hangs.

Scenario questions

  1. 01 Your device resets randomly in the field. How do you debug it?

    How to answer: Read the reset-reason register, check for stack overflow, watchdog timeouts, brown-out and power supply issues, and add persistent logging before the reset.

  2. 02 Design firmware that reads a sensor every 10 ms and sends the data over UART.

    How to answer: Use a timer interrupt or RTOS task for sampling, a ring buffer between producer and consumer, and DMA or interrupt-driven UART transmission.

  3. 03 An I2C sensor is not responding. What do you check?

    How to answer: Wiring and pull-up resistors, the device address, bus speed, then probe SDA and SCL with a logic analyser to see whether you get an ACK.
Then comes the HR round Almost every interview ends with HR questions about you, your plans and your salary expectations. See the common ones and how to answer them.

Resume tips for this role

  • Name the exact microcontrollers, boards, RTOS and protocols you have worked with.
  • Describe projects in terms of hardware and outcome, such as "designed a CAN-based data logger for an EV battery pack".
  • Mention lab tools you can use: oscilloscope, logic analyser, JTAG debugger.
  • Include relevant coursework or internships at semiconductor or automotive companies.

This guide is written by the JOBSPOT 360 team from common interview patterns for this kind of role. It is not provided by any employer, and real interviews will differ. Read our editorial policy.