Technical screening questions
Ask for one example per question and listen for specifics.
- How do you debug an intermittent hardware fault? A good answer: Isolate with a logic analyzer, test timing and rule out software.
- What are the trade-offs of using an RTOS? A good answer: Scheduling and concurrency against overhead.
- How do you manage memory on a small device? A good answer: Static allocation, stack sizing and avoiding fragmentation.
- Explain how I2C and SPI differ. A good answer: Addressing, speed and wiring.
- How do you handle interrupts safely? A good answer: Short handlers, volatile access and shared data.
Quick screening questions
Use these when you have only a few minutes.
- Which MCUs and RTOS?
- Describe a hardware bug you traced.
- How do you test firmware?
What separates the levels
Match the level to the requirement before you submit.
- Junior: implements drivers and fixes bugs.
- Mid: owns subsystems.
- Senior: designs firmware architecture and power strategy.
Red flags
Any of these is a reason to probe further.
- Only application-level C++.
- No hardware debugging.
- Cannot discuss interrupts.
Tools you should hear mentioned
An embedded software engineer with real experience usually names several of these without prompting.
- C and C++
- RTOS (FreeRTOS, Zephyr)
- JTAG debuggers
- I2C, SPI and UART
- Oscilloscope and logic analyzer
- Git
Run the call well
Ask for the last project first, then dig into the second or third question. Take notes on versions, team size and outcomes, and record them with the submission so the vendor’s later technical interview does not surprise you.
Frequently asked questions
How long should an embedded software engineer screening call take?
Fifteen to twenty minutes is enough to cover the project, three technical questions and availability, rate and work authorization.
Do recruiters need to know the technology?
Working vocabulary is enough. Use the sourcing guide for the role and listen for specifics instead of judging technical depth yourself.