Learn embedded systems. Prove it in the interview.
Basic C is enough. Solve firmware challenges on emulated STM32, nRF52 and ESP32, get hardware-level test feedback, then study the written and video walkthroughs. Hiring teams run real embedded interviews on the same system.
- Target hardware
- STM32 · nRF52 · ESP32
- Real firmware
- C · HAL · Arduino · IDF
- Peripherals
- I²C · UART · GPIO
- Interview-style grading
- Timed · auto-graded
1void userCode(void) {234567891011}
Console
$ make -j8arm-none-eabi-gcc -mcpu=cortex-m4 -Os -c Core/Src/userCode.ctext 21904 data 128 bss 3072 dec 25104$ hexbench emulate --target stm32f407vgUART4 ▸ Temp: 23.40 Ctarget: halted at exit tracer, ok
Resource Usage
Target Board
STM32F407VG
Test Results
N/A
LeetCode won't save you in an embedded interview
HexBench trains you on the right side because it is built from an actual interview system.
Proxy prep
Generic interview prep
- Array-reversal puzzles
- No registers, no datasheets
- Nothing compiles for a target
- No clock pressure that matches the real thing
Executable prep
The real embedded interview
- Read a spec like a datasheet
- Write C against a real vendor HAL or SDK
- Wire the sensor, pass hardware tests
- All of it under a timer
$ make -stext 21904 data 128 bss 3072$ hexbench emulate --target stm32f407vgi2c1: START · addr 0x76 · W · ACKtest 1 read_id .............. passtest 2 burst_read ........... passtest 3 timeout_guard ........ passtest 4 wiring_check ......... pass
Flash
21.4 KB
RAM
3.1 KB
Target
STM32F407VG
Tests
4 / 4 pass
The training system
The real interview environment
The same browser IDE, STM32, nRF52 and ESP32 emulation, and auto-grading that power actual HexBench interviews, with autocomplete, clangd diagnostics, and a real GDB debugger.
browser ide · stm32 / nrf52 / esp32 emulation · clangd · gdb
Focused drills on the fundamentals
Topic-based practice sets covering exactly what interviews test: peripherals, interrupts, and memory.
peripherals · interrupts · memory
Pressure reps
A per-exercise timer, randomized test values you can't hardcode around, and Flash/RAM budgets. Practice the conditions, not just the content.
timer · randomized tests · flash/ram budget
Verified proof of skill
Certificates are earned by clearing real firmware challenges on emulated hardware. They are never just handed out.
emulated hardware · earned, never granted
Interview practice
- 01FreeRTOS Basics
- 02Task Management
- 03Interrupt Handling
- 04UART Communication
- 05I²C & UART Protocols
- 06GPIO & LED Control
- 07Timers & RTC
- 08Debugging & Hardware Wiring
Preparing for a technical interview? Connect the concepts above to a firmware task, test feedback and a review of your decisions. See the interview practice guide
Run a mock interview end to end
Scroll through an interview-style challenge: read the spec, write firmware under the clock, wire the hardware, and pass the hardware tests. It is the same loop used in a real embedded interview.
Blink with SysTick
Easy - GPIO
UART ring buffer
Hard - Drivers
Read SHT45 over I2C
Medium - Sensors
FreeRTOS task sync
Medium - RTOS
Walk into the interview with proof
A portfolio of passed challenges
Every hardware challenge you pass becomes part of a track record you can show.
Proof of readiness
Clear every challenge to earn a verified certificate that an interviewer can inspect.
Timed reps under interview conditions
You have already worked under the clock, so the real interview will not be the first time.
Real debugging experience
GDB on emulated hardware, not printf-and-pray.
Resource-aware habits
Flash and RAM numbers on every submission, so you think in constraints from day one.
Simple, transparent pricing
Start free, then unlock every interview-style challenge when you're ready. No hidden fees.
Questions before you start
Straight answers for anyone learning embedded systems or preparing for a firmware interview.
How do I start learning embedded systems?
Get comfortable with C first: variables, functions, loops, pointers and bit operations. Then learn the peripherals in order: GPIO, timers and interrupts, UART, I2C and SPI, sensors, and finally an RTOS such as FreeRTOS. On HexBench each step is a firmware challenge that runs on an emulated STM32, nRF52 or ESP32 board and is checked by hardware-level tests, so you learn by writing firmware rather than only reading about it.
Do I need a development board or a local toolchain?
No. You write, build, run and debug the firmware in the browser, and it runs on emulated microcontrollers in the cloud. A real board is still worth buying later for what emulation cannot show, such as analog noise and exact timing on real silicon.
Is basic C enough?
Yes. HexBench does not teach C from scratch, but the beginner challenges need no prior embedded experience.
Are there solutions and explanations?
Many challenges include a written walkthrough and a video that explain the solution step by step. Every run also shows which hardware tests passed or failed, so you can see what your firmware actually did.
Is there a LeetCode for embedded systems?
That is what HexBench is built for: graded challenges with difficulty levels, but the problems are firmware for microcontrollers. Solutions are judged by what the hardware does (pin states, UART output, bus traffic, flash and RAM use), not by algorithm puzzles in a desktop language.
Will it help me prepare for embedded interviews?
Yes. You practice timed firmware tasks, debugging with GDB and resource-aware code on the same platform companies use to run real embedded interviews.
Is it free?
A set of challenges is free to solve. The full catalog is part of the paid plan.
Hiring embedded engineers?
HexBench also runs live and async embedded interviews for teams.