🚗 EV Embedded Software Engineer Interview Questions with Answers

If you are preparing for an Embedded Software Engineer role in the Electric Vehicle (EV) industry, technical interviews often focus on embedded C, microcontrollers, RTOS, CAN communication, and EV-specific modules like Battery Management Systems (BMS) and motor control. To help you succeed, we’ve compiled the top 25 interview questions most frequently asked by EV companies. These questions will guide you in revising key concepts and demonstrating practical problem-solving skills required for EV embedded systems.

🔹 Core Embedded Systems Questions

1. Difference between a microcontroller and a microprocessor?

• Microcontroller → CPU + memory + peripherals on a single chip, used for control tasks (e.g., ECU in EV).
• Microprocessor → Only CPU, needs external memory & peripherals, used in high-performance systems (e.g., infotainment).

2. What is an interrupt? How is it handled?

• An interrupt is a signal that temporarily halts the CPU to handle an urgent task.
• Handled using Interrupt Service Routine (ISR), then control returns to main program.

3. How does CAN communication work? Why in automotive?

• CAN = Controller Area Network, a serial bus for ECUs.
• Uses priority-based arbitration, high reliability, error detection.
• Standard in automotive due to robustness & real-time capabilities.

4. Advantages of RTOS in automotive systems?

• Deterministic response.
• Priority-based scheduling for safety-critical tasks.
• Better modularity & debugging.
• Essential for BMS, Motor Control, ADAS.

5. Explain memory-mapped I/O.

• Peripherals are assigned specific addresses in memory space.
• CPU reads/writes to these addresses → directly controls hardware.

6. What is debouncing? How is it implemented?

• Mechanical switches cause multiple transitions (bouncing).
• Implemented in software (delay/filtering) or hardware (RC filter, Schmitt trigger).

7. Debugging an embedded system without OS/console?

• Use LED toggling, UART logs, JTAG/SWD debugger, oscilloscopes, logic analyzers.

8. Polling vs. interrupt-driven systems?

• Polling: CPU keeps checking status (wastes CPU cycles).
• Interrupt: CPU only reacts when needed (efficient).
• For EVs → interrupt-driven is preferred (real-time response).

🔹 Programming & Embedded C

9. Program to toggle LED with delay (pseudo C):

while(1) {
   LED = 1; delay_ms(500);
   LED = 0; delay_ms(500);
}

10. What is volatile keyword in C?

• Tells compiler a variable can change anytime (e.g., hardware register, ISR).
• Prevents unwanted optimizations.

11. How to avoid race conditions in embedded C?

• Use mutexes, semaphores, disabling interrupts, or atomic operations.

12. Structure vs. Union in C?

• Structure: All members occupy separate memory.
• Union: Members share same memory.
• Useful for interpreting sensor data in different formats.

13. How to optimize C code for speed & memory?

• Use inline functions, avoid recursion, optimize loops, fixed-point math, reduce global variables.

🔹 Automotive / EV-Specific

14. What is AUTOSAR?

• AUTOSAR (Automotive Open System Architecture) → Standardized software framework for automotive ECUs.
• Promotes reusability, safety, and scalability.

15. Battery Management System (BMS) role in EVs?

• Monitors voltage, current, temperature of cells.
• Manages charging/discharging, balancing, safety cut-offs.

16. Communication protocols in EVs?

• CAN, LIN, FlexRay, Automotive Ethernet.
• CAN = control, LIN = simple nodes, FlexRay = safety-critical, Ethernet = high-speed data (ADAS).

17. Functional safety in EVs (ISO 26262)?

• Ensures system reliability & safety under faults.
• Uses ASIL (Automotive Safety Integrity Level) classification.
• Requires fail-safe mechanisms, redundancy.

18. Regenerative braking (embedded perspective)?

• During braking, motor acts as generator, converts kinetic energy → electrical energy.
• Embedded system controls motor inverter & battery charging.

19. Motor control in EVs (BLDC, PMSM)?

• Use PWM + feedback loops (FOC – Field Oriented Control).
• Requires current, position, speed sensors + control algorithms.

20. Safety for overcurrent/overheating?

• Use sensors, watchdog timers, cutoff circuits.
• Implement software limits + hardware protection.

🔹 RTOS & Real-Time Behavior

21. Hard vs. soft real-time systems?

• Hard RT: Missing deadline = system failure (e.g., airbag ECU).
• Soft RT: Occasional delays tolerated (e.g., infotainment).

22. Task prioritization in RTOS BMS?

• Safety-critical (overvoltage/overcurrent) → highest priority.
• Communication (CAN, logging) → medium.
• Background tasks (SOC calculation) → lowest.

23. Deadlock in RTOS? How to avoid?

• Deadlock: Two/more tasks waiting indefinitely for each other’s resources.
• Avoid by resource ordering, timeouts, priority inheritance.

24. Task scheduling in FreeRTOS?

• Preemptive priority-based scheduler.
• Highest-priority ready task always runs.

🔹 Testing & Debugging

25. How to test safety-critical embedded software in EVs?

• Unit testing, integration testing.
• Hardware-in-the-loop (HIL) simulation.
• Stress & fault injection testing.
• Compliance with ISO 26262.

26. Debugging tools (examples)?

• JTAG, SWD, Logic Analyzers, Oscilloscopes, UART logs, ETM (trace modules).

27. Simulating hardware without physical EV?

• Use HIL simulators, MATLAB/Simulink models, Proteus/Multisim simulations.
• Virtual ECUs to test software before real deployment.