Embedded firmware interview practice questions

Embedded firmware interview practice questions you answer by writing code. Each one is an embedded C practice problem: write real C, compile it for ARM Cortex-M4, and run it on a simulated STM32F4 with deterministic scoring. The embedded coding challenges span GPIO, UART, timers, SPI, I2C, DMA, watchdog, and RTOS.

All challenges

• Readout (UART)
• Heartbeat (GPIO)
• Traffic Light (GPIO)
• Light Switch (GPIO)
• Doorbell (Interrupts)
• Dispatcher (UART)
• Wire Tap (UART)
• Stopwatch (Timers)
• Roll Call (SPI)
• Thermometer (I2C)
• Standstill (Motor control)
• Nameplate (Foundations)
• As Found (Foundations)
• Wait for It (Foundations)
• Upside Down (Foundations)
• Timekeeper (Foundations)
• The Fly (Foundations)
• Weather Report (Foundations)
• Tuning Fork (Foundations)
• Floor Plan (Foundations)
• Calling Card (CAN)
• Cocktail Party (CAN)
• Big Red Button (CAN)
• Vigil (Timers)
• First Shift (RTOS)
• Right of Way (RTOS)
• Baton (RTOS)
• Hopper (RTOS)
• Ghost on the Bus (SPI)
• Knock (Interrupts)
• Tally (Interrupts)
• Night Watch (watchdog)
• First Turn (Motor control)
• Cruise (Motor control)
• Stampede (Interrupts)
• Dead Air (I2C)
• Fallback (I2C)
• Dial Tone (UART)
• Cold Start (System)
• Uplink (Interrupts)
• Chokepoint (Interrupts)
• Dead Man's Switch (watchdog)
• Seesaw (RTOS)
• Handshake (RTOS)
• Turnstile (RTOS)
• Behind Schedule (RTOS)
• Server Room Monitor (System)
• Famine (RTOS)
• Clockwork (RTOS)
• Quiet Pulse (RTOS)
• Stops at Twelve (RTOS)
• Kennel (RTOS)
• Conveyor (DMA)
• Intake (DMA)
• Flood (DMA)
• Afterthought (I2C)
• Flight Recorder (SPI)
• Conductor (Timers)
• Cascade (SPI)
• Stonewall (Interrupts)
• Drift (UART)
• Switchboard (GPIO)
• Parrot (UART)
• Steady (GPIO)
• Postcard (SPI)
• Scroll (I2C)
• Phantom (GPIO)
• Crossed Wires (I2C)
• Lost in Translation (UART)
• Quicksand (UART)
• Census (I2C)
• Identity Crisis (SPI)
• Automaton (GPIO)
• Dispatch Bay (CAN)
• Flatline (CAN)
• Hibernation (Low power)
• Echo Tail (UART)
• Redline (Motor control)
• Seized (Motor control)
• Slingshot (Motor control)
• Backspin (Motor control)
• Quiet Mode (Motor control)
• Runaway (Motor control)
• Out of Step (Motor control)
• Treading Water (Motor control)

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