{"id":4980,"library":"lpc-checksum","title":"LPC Checksum","description":"A Python script designed to calculate LPC firmware checksums, based on the C version by Roel Verdult. It functions both as a standalone application and as a Python module that can be integrated into build environments. The current version is 3.0.0, but its release cadence is stalled, with the last release approximately three years ago.","status":"maintenance","version":"3.0.0","language":"en","source_language":"en","source_url":"https://github.com/basilfx/lpc_checksum","tags":["lpc","checksum","firmware","microcontroller","nxp","embedded"],"install":[{"cmd":"pip install lpc-checksum","lang":"bash","label":"Install via pip"}],"dependencies":[{"reason":"Required for handling Intel HEX file formats.","package":"intelhex","optional":false}],"imports":[{"note":"The primary function `checksum` is accessed directly from the imported module.","symbol":"checksum","correct":"import lpc_checksum"}],"quickstart":{"code":"import lpc_checksum\nimport os\n\n# Create a dummy binary file for demonstration\ndummy_firmware_path = 'firmware.bin'\nwith open(dummy_firmware_path, 'wb') as f:\n    f.write(b'\\x00\\x00\\x00\\x20\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00' \\\n            b'\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00' \\\n            b'\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00')\n\n# Calculate and inject the checksum\ntry:\n    # The checksum function modifies the file in place by default\n    # or returns the checksum if read_only=True\n    print(f\"Calculating checksum for {dummy_firmware_path}\")\n    checksum_value = lpc_checksum.checksum(dummy_firmware_path, read_only=True)\n    print(f\"Calculated checksum (read-only): 0x{checksum_value:08x}\")\n\n    # To actually write the checksum to the file:\n    lpc_checksum.checksum(dummy_firmware_path)\n    print(f\"Checksum injected into {dummy_firmware_path}\")\n\nexcept Exception as e:\n    print(f\"An error occurred: {e}\")\nfinally:\n    # Clean up the dummy file\n    if os.path.exists(dummy_firmware_path):\n        os.remove(dummy_firmware_path)\n        print(f\"Cleaned up {dummy_firmware_path}\")\n","lang":"python","description":"This quickstart demonstrates how to import `lpc_checksum` and use its `checksum` function to calculate and optionally inject the correct checksum into a dummy binary firmware file. The `checksum` function modifies the input file in place by default."},"warnings":[{"fix":"Ensure `lpc_checksum.checksum(filepath)` is run on your firmware binary as part of your build process before flashing to an NXP LPC microcontroller.","message":"LPC microcontrollers require a specific checksum at address 0x1C in the interrupt vector table for the firmware to boot correctly. If this checksum is missing or incorrect (e.g., if a standard GNU toolchain doesn't generate it), the device will not boot or will enter ISP mode. This library directly addresses this issue.","severity":"gotcha","affected_versions":"All versions, applies to target hardware requirements."},{"fix":"Always use the latest stable version of `lpc-checksum`. When implementing similar checksum logic, ensure correct 32-bit unsigned integer arithmetic, typically using bitwise AND `& 0xFFFFFFFF` to handle overflows if not implicitly handled by the language/platform.","message":"When calculating 32-bit checksums, improper handling of integer overflow can lead to incorrect results. An earlier version (v2.1.2) had a bug where modulo (%) was incorrectly used instead of bitwise AND (&) for 32-bit overflow, leading to discrepancies with C-based calculations. While fixed in current versions, it highlights a critical detail in checksum implementation.","severity":"gotcha","affected_versions":"< 2.1.2 (bug fixed in 2.1.2, but principle applies generally)"},{"fix":"Be aware that active maintenance may be limited. Consider contributing to the project if you encounter issues or require new features, or evaluate if the existing functionality meets your long-term needs without further updates.","message":"The `lpc-checksum` library's release cadence is stalled, with the last release (v3.0.0) dating back approximately three years ago. This indicates a lack of active development, which could mean slower responses to bug reports or no new feature additions.","severity":"deprecated","affected_versions":"3.0.0 and potentially future versions."}],"env_vars":null,"last_verified":"2026-04-12T00:00:00.000Z","next_check":"2026-07-11T00:00:00.000Z"}