Is there a LeetCode for embedded systems?

Use three practice sessions to connect your C knowledge to working firmware. Choose the topics that match the job description.

1. Explain the C and hardware concepts

   Review pointers, bit masks, volatile, memory lifetime and interrupt shared state. Explain which problems volatile solves and which still need synchronization. Read the task and state your assumptions before coding.

2. Implement and test a firmware task

   Choose a GPIO, timer, serial communication or sensor challenge from the catalog. Write the firmware, run the tests and investigate failures. Practise explaining timeouts, boundary cases and resource constraints.

3. Review your decisions out loud

   Explain why you chose the implementation, how you would debug it on a physical board and what could fail. Use a written or video walkthrough where available, then retry without looking at the solution.

These examples come from the current public catalog. Open a brief to check its target, requirements and access. During a Pioneer event, the brief also shows whether the task is part of the active set or opens afterwards.

• Seatbelt Reminder Lamp

  Nano 33 BLE · Arduino · Easy

  On an Arduino Nano 33 BLE, flash a belt warning lamp when the ignition is on and the belt stays unlatched for two seconds, and start the grace period over every time the situation begins again.

• Charger Status Indicator

  Nano 33 BLE · Arduino · Easy

  On an Arduino Nano 33 BLE, turn three active-low charger status lines into one LED: off, steady, slow blink or fast blink, chosen by priority, with a fault overriding everything and one STATE line per change.

• Greenhouse Climate Monitor

  STM32 · HAL · Medium

  The HS3001 is a small temperature and humidity sensor that talks over I2C. Your job is to wire it up (including the pull-up resistors on the I2C lines), read its 4 byte measurement, work out the temperature and humidity from those bytes, and send the results out over UART. It's the sort of code you'd write for any board that needs to keep track of its surroundings.

Browse all challenges

• The code runs on a microcontroller, not a desktop: memory is small and there is no operating system by default.
• Correctness means hardware behavior: the right pin toggles at the right time, the right bytes leave the UART, the sensor is read correctly.
• Peripherals, interrupts and timing matter more than clever data structures.
• Interviewers ask about volatile, interrupts, race conditions, bit manipulation, buses and debugging, and often want to see working firmware.

• Bit manipulation and register access in C.
• GPIO, debouncing, timers and interrupt handlers.
• UART output and simple command parsing.
• I2C sensor reads, unit conversion and thresholds.
• Ring buffers, state machines and FreeRTOS tasks and queues.
• Debugging with a debugger, and reasoning about flash and RAM use.

1. Pick a challenge by topic and difficulty (easy, medium, hard).
2. Write embedded C in a browser IDE with autocomplete and diagnostics.
3. Run it: the firmware is built and executed on an emulated STM32, nRF52 or ESP32 board.
4. See which hardware-level tests passed, debug with GDB, and check flash and RAM.
5. Study the written walkthrough and video, where the challenge includes them.

Browse all challenges · How to learn embedded systems: where to start after C

HexBench does not teach C from zero, and emulation does not cover every peripheral or every analog effect of a physical board. It is a place to build and prove firmware skills quickly; a real board is still the next step for hardware-specific work.