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HeapCrash / Challenges

Embedded bug-hunt challenges

74 pieces of plausible firmware, each with real bugs that pass a bench test and fail in the field. Find them, explain what breaks, fix them, and build your fix against a mock Cortex-M or Linux target.

Drivers & ISRs 9

UART receive ring bufferDrivers & ISRs · Medium · 4 bugs · ~6 min SPI NOR flash driverDrivers & ISRs · Medium · 4 bugs · ~6 min STM32 HAL I2C readDrivers & ISRs · Warm-up · 4 bugs · ~4 min Button debounce in an EXTI ISRDrivers & ISRs · Warm-up · 3 bugs · ~4 min Independent watchdog usageDrivers & ISRs · Medium · 3 bugs · ~5 min Flags shared with an ISRDrivers & ISRs · Medium · 2 bugs · ~5 min Runtime baud-rate changeDrivers & ISRs · Warm-up · 3 bugs · ~5 min CAN node goes silent for goodDrivers & ISRs · Medium · 3 bugs · ~7 min SPI writes that don't stickDrivers & ISRs · Medium · 3 bugs · ~6 min

RTOS 11

FreeRTOS sensor pipelineRTOS · Hard · 5 bugs · ~8 min Sharing SPI between tasksRTOS · Medium · 3 bugs · ~6 min Logging through a queueRTOS · Warm-up · 3 bugs · ~4 min Critical sections and scheduler locksRTOS · Medium · 4 bugs · ~5 min Periodic control loopRTOS · Medium · 3 bugs · ~5 min Nested mutexes under loadRTOS · Hard · 3 bugs · ~8 min Task check-in watchdogRTOS · Medium · 3 bugs · ~7 min OS sanity watchdog hooksRTOS · Hard · 3 bugs · ~7 min Synchronous request and replyRTOS · Hard · 3 bugs · ~8 min Report task stack overflowRTOS · Medium · 3 bugs · ~6 min Encoder ISR at top priorityRTOS · Medium · 3 bugs · ~6 min

Timing 6

Tick timeouts and delaysTiming · Warm-up · 3 bugs · ~4 min 64-bit microsecond timestampsTiming · Medium · 2 bugs · ~5 min PWM duty and frequency controlTiming · Medium · 5 bugs · ~6 min Fixed-point speed loopTiming · Medium · 3 bugs · ~6 min Flow meter input captureTiming · Medium · 3 bugs · ~6 min Microsecond delays that hangTiming · Medium · 3 bugs · ~6 min

Memory & C 9

Casting a byte stream to a structMemory & C · Medium · 4 bugs · ~6 min Integer promotion trapsMemory & C · Medium · 3 bugs · ~5 min Strings on the stackMemory & C · Warm-up · 3 bugs · ~4 min Array helpers with memcpyMemory & C · Warm-up · 3 bugs · ~4 min Heap use in a message handlerMemory & C · Medium · 3 bugs · ~5 min Register access macrosMemory & C · Warm-up · 3 bugs · ~4 min Packing a log recordMemory & C · Medium · 3 bugs · ~6 min Status register as C bitfieldsMemory & C · Hard · 3 bugs · ~7 min Helpers shared by two tasksMemory & C · Medium · 3 bugs · ~6 min

Protocols 10

Serial command parserProtocols · Warm-up · 3 bugs · ~4 min TLV provisioning parserProtocols · Hard · 4 bugs · ~7 min Building a framed packetProtocols · Medium · 3 bugs · ~6 min RS-485 Modbus RTU linkProtocols · Medium · 3 bugs · ~5 min BLE characteristic write handlerProtocols · Medium · 4 bugs · ~6 min Wi-Fi reconnect handlerProtocols · Medium · 3 bugs · ~6 min CAN receive filter and handlerProtocols · Medium · 3 bugs · ~7 min RS-485 transmit with DMAProtocols · Medium · 3 bugs · ~7 min Stuck I2C bus after resetProtocols · Medium · 3 bugs · ~7 min Accelerometer readings make no senseProtocols · Warm-up · 3 bugs · ~5 min

Low power 5

Entering and leaving STOP modeLow power · Medium · 3 bugs · ~5 min Battery voltage measurementLow power · Medium · 3 bugs · ~5 min Sleep until there's workLow power · Hard · 3 bugs · ~7 min Sleep current sixty times too highLow power · Medium · 3 bugs · ~6 min RTC wake-up from STOP 2Low power · Medium · 3 bugs · ~7 min

Boot & OTA 8

Bootloader jump to applicationBoot & OTA · Hard · 3 bugs · ~6 min Switching OTA slotsBoot & OTA · Medium · 3 bugs · ~5 min Saving settings to internal flashBoot & OTA · Medium · 3 bugs · ~5 min Data retained across resetsBoot & OTA · Hard · 3 bugs · ~6 min Bootloader image verificationBoot & OTA · Hard · 3 bugs · ~8 min Settings and calibration in one pageBoot & OTA · Medium · 4 bugs · ~7 min OTA chunk writerBoot & OTA · Hard · 3 bugs · ~8 min Anti-rollback check in the bootloaderBoot & OTA · Hard · 3 bugs · ~7 min

DMA & graphics 6

ADC with circular DMADMA & graphics · Hard · 3 bugs · ~7 min Logging over UART with DMADMA & graphics · Medium · 3 bugs · ~5 min LTDC double bufferingDMA & graphics · Hard · 3 bugs · ~7 min LVGL flush callback with DMA2DDMA & graphics · Medium · 3 bugs · ~5 min Touch controller interruptDMA & graphics · Medium · 4 bugs · ~6 min SPI DMA on a cached coreDMA & graphics · Hard · 3 bugs · ~7 min

Embedded Linux 6

Character driver read()Embedded Linux · Medium · 3 bugs · ~7 min Serial GPS reader on LinuxEmbedded Linux · Medium · 4 bugs · ~6 min Ping diagnostic on a Linux gatewayEmbedded Linux · Medium · 3 bugs · ~6 min GPIO through /dev/memEmbedded Linux · Medium · 3 bugs · ~6 min Touch driver interrupt handlerEmbedded Linux · Hard · 3 bugs · ~7 min ADC over spidevEmbedded Linux · Medium · 3 bugs · ~6 min

Test & validation 4

Production SRAM testTest & validation · Medium · 3 bugs · ~6 min ADC self-test at bootTest & validation · Warm-up · 3 bugs · ~5 min End-of-line test firmwareTest & validation · Medium · 3 bugs · ~6 min Startup flash CRC self-testTest & validation · Medium · 3 bugs · ~6 min

Every challenge runs in the browser. No install, and the bug hunts are free.

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