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Changelog

All notable changes to this project are documented here. Format follows Keep a Changelog. Versions are tagged as vX.Y.Z in the repository.

[v1.0.0] - 2026-05-09

✨ Added

Core bootloader

  • 🔐 AES-128-CBC encrypted firmware transport — per-image IV embedded in the firmware header; key injected at compile time as a preprocessor definition
  • ✅ CRC-32/IEEE 802.3 integrity verification — computed over the complete decrypted firmware image before any flash write is committed
  • ⚛️ Atomic flash write — application reset vector deferred and written last, only after the full-image CRC passes; a partial or interrupted transfer can never produce a bootable image
  • 🔑 64-bit device ID check — firmware built for a different target is rejected at header validation; prevents cross-device flashing
  • 🔘 Push-button stay-alive — press-release cycle extends the bootloader window to PUSH_BUTTON_TIMEOUT (300 s default) without host intervention; button held at reset extends to PUSH_BUTTON_DET_TIMEOUT (60 s default)
  • ⏱️ Configurable timeouts — START_TIMEOUT, COMM_TIMEOUT, PUSH_BUTTON_TIMEOUT, PUSH_BUTTON_DET_TIMEOUT (all in 100 ms ticks via bl_hw_config.h)
  • ⚙️ Selectable CRC implementation — CRC_MODULE=SW (platform-independent) or CRC_MODULE=HW (STM32 CRC peripheral), chosen at CMake configure time; both implementations expose the same crc_api.h interface

Hardware targets

Target MCU Core Flash CRC modes
STM32G070RB STM32G070RBTx Cortex-M0+ 128 KB SW + HW
STM32G071RB STM32G071RBTx Cortex-M0+ 128 KB SW + HW
STM32G474RE STM32G474RETx Cortex-M4F 512 KB SW + HW
ATmega328P (Arduino Uno R3) ATmega328P AVR8 32 KB SW

All STM32 targets occupy the first 4 KB of flash; the application region starts immediately after.

Architecture

  • 🧩 Platform-independent core (src/main_app.c) — all hardware calls delegated to a six-driver interface (bl_usart_drv, bl_flash_drv, bl_key_drv, bl_status_led_drv, core_drv, crc_api)
  • 📐 STM32_TEMPLATE porting skeleton with TODO-annotated driver stubs for adding new STM32 targets
  • Single bl_hw_config.h per target — flash map, timing constants, and peripheral settings in one place

Unit tests

  • 🧪 44 tests for the bootloader core (test/MAIN_APP) — full protocol FSM, header validation, page write, CRC check, exit conditions, LED/key logic
  • 🧪 33 tests for the CRC module (test/CRC) — algorithm correctness and all public API functions
  • Tests run on the host with Unity + CMock; no hardware required
  • CMock-generated mocks isolate the core from all hardware drivers
  • gcovr code coverage with ≥ 90 % line threshold; HTML report generated automatically

Build system

  • 🛠️ CMake + Ninja with predefined flash, erase, reset targets — STM32_Programmer_CLI and avrdude auto-detected at configure time
  • AES key accepted in three formats: C initialiser list, plain hex string, colon-separated hex
  • AVR targets: additional write_fuses, read_fuses, read_flash targets

CI / CD

  • 🤖 GitHub Actions CI pipeline — builds all HW targets (SW CRC + HW CRC variants), runs unit tests, enforces ≥ 90 % coverage, cppcheck static analysis, Lizard complexity (CCN ≤ 12)
  • 📄 MkDocs Material documentation site with auto-deployed coverage and complexity reports on every merge to main
  • 🚀 Automated release workflow — detects new vX.Y.Z entries in CHANGELOG.md on PR merge and creates a tagged GitHub release with the extracted release notes

Tool ecosystem

  • Compatible with EncryptBIN for producing AES-CBC encrypted firmware packages on the host
  • Compatible with SecureLoader for uploading encrypted packages to the target over serial (CLI + GUI)