Roles they hire for
- System firmware engineer (RTOS BSP)
- System control and power firmware engineer
- Application and system firmware engineer
What they emphasise
- RTOS bootstrapping and board support packages
- Scheduling, synchronization, exception handling and IPC
- Memory hierarchies, DMA, timers and interrupt controllers
- Power and system-state sequencing as state machines
Brush up on
RTOS internalsDMA and cachesInterrupt controllersState machinesARM exceptionsPower optimization
How the rounds usually run
A typical consumer hardware loop for embedded roles. Companies vary by team and seniority.
Recruiter screen
- Background, role fit and logistics
Example: Walk me through your current project in two minutes.
Technical phone screen: C coding
- Live C coding: data structures, bit manipulation, memory
- Explaining your code and edge cases out loud
Example: Implement memmove and explain how you handle overlap.
Loop: embedded system design
- Architecture for a device feature end to end
- Power, memory and real-time trade-offs
Example: Design firmware for a wireless earbud's charging case.
Loop: RTOS, concurrency and debugging
- Scheduling, synchronization, priority inversion
- Hardware and software debugging with scopes and schematics
Example: Explain priority inversion and two ways to prevent it.
Hiring manager and behavioural
- Ownership, cross-functional work and judgement
Example: Tell me about a time you shipped under a hard deadline. What did you cut?
Practice questions
Original questions written for Apple's focus areas, not leaked ones.
- Design the state machine for a device's power sequencing: off, booting, on, sleep and fault. Which events and timeouts matter?
- Implement a fixed-size message queue for an RTOS. How do you handle ISR producers and priority?
- A DMA transfer completes but the CPU reads stale data. Walk through every cause you'd check.
- How does a context switch work on Cortex-M, step by step, and what does PendSV do?
- You have 64 KB of RAM for an RTOS, a protocol stack and logging. How do you budget and verify it?
Your prep playlist
UART receive ring bufferDrivers & ISRs · Medium · 4 bugs · ~6 min64-bit microsecond timestampsTiming · Medium · 2 bugs · ~5 minLogging over UART with DMADMA & graphics · Medium · 3 bugs · ~5 minFlags shared with an ISRDrivers & ISRs · Medium · 2 bugs · ~5 minSleep until there's workLow power · Hard · 3 bugs · ~7 minSynchronous request and replyRTOS · Hard · 3 bugs · ~8 minReport task stack overflowRTOS · Medium · 3 bugs · ~6 minPacking a log recordMemory & C · Medium · 3 bugs · ~6 minHelpers shared by two tasksMemory & C · Medium · 3 bugs · ~6 min
Design rounds to practise
Sources
Take an AI mock round styled on Apple, with follow-ups that probe what you missed.
Start a mock round