Firmware interview practice
An interview workbench for embedded engineers. Solve real C problems, follow diagnostics back to your code, and build the fundamentals behind reliable firmware.
Bit operations to RTOS. Practice with a real C judge.
#include <stdint.h> int main(void) { uint8_t packet[4] = {0xAA, 0x10, 0x01, 0x00}; // The fifth byte is outside this buffer. packet[4] = 0xFF; return 0;}Line 7: Out-of-bounds write: 0 bytes past the end of packet, which is 4 bytes.
Check the index against the object's length.
Inside the workbench: source code, executable tests, and precise feedback.
Practice index
4 tracks
Coding is only one part of the interview. Move between implementation, architecture, technical questions, and the fundamentals behind them.
101 problemsC11 · bitwise
Write and run real embedded C against tests — bitmasks, registers, ring buffers, and protocol parsing.
16 lessonsISR · MMIO
A dependency-ordered firmware curriculum — the C contract, boot, registers, interrupts, RTOS, and field reliability — with the interview depth expected at each level.
9 promptsRTOS · OTA
Open-ended firmware architecture prompts: schedulers, OTA updates, drivers, and fault recovery.
100 questionsQ&A · debug
A searchable bank of conceptual questions interviewers actually ask, with concise answers.
Curriculum
10 topics
The catalog follows the work: registers, protocols, shared state, timing, memory, and recovery.
Pointers, volatile, fixed-width types, and the C that runs on metal.
19prob
Masks, shifts, and register flags without disturbing neighbors.
22prob
Working rhythm
3 stages
Every exercise keeps the feedback loop short enough to repeat, while leaving the reasoning to you.
Read
Start with a focused embedded problem statement and an explicit contract, not a puzzle wrapped in a story.
Implement
Work through register operations, buffers, protocols, and systems code in the browser-based C workspace.
Review
Check the result against a expected output and inspect the failing case without leaving the problem.
Example problem
1 / 101
A direct statement, an exact function contract, and cases you can reason through before writing code.
Modify a single bit of an 8-bit hardware register using masks — without touching the others.
uint8_t set_bit(uint8_t reg, uint8_t bit);
uint8_t clear_bit(uint8_t reg, uint8_t bit);
uint8_t toggle_bit(uint8_t reg, uint8_t bit);A short email when we publish new problems or study material. No weekly quota.
Drive peripherals through volatile register pointers.
7prob
UART, SPI, and I2C framing, parsing, and checksums.
12prob
Tasks, ISRs, atomicity, and shared-state race conditions.
9prob
Inspect broken firmware and explain the root cause.
5prob
Non-blocking timing, debouncing, and protocol framing.
8prob
Image integrity, CRCs, and safe OTA update flows.
8prob
Architect firmware: schedulers, drivers, and recovery.
4prob
Static allocation, pools, and fragmentation-free design.
7prob