| Offset | Size | Field | Description | | :--- | :--- | :--- | :--- | | 0 | 4 | magicStart0 | First magic number, 0x0A324655 ("UF2\n") | | 4 | 4 | magicStart1 | Second magic number, 0x9E5D5157 | | 8 | 4 | flags | Specifies special properties of the block | | 12 | 4 | targetAddr | The address in flash memory where the data should be written | | 16 | 4 | payloadSize | Number of bytes of actual data in this block (often 256) | | 20 | 4 | blockNo | Sequential block number, starting at 0 for the first block | | 24 | 4 | numBlocks | Total number of blocks in the entire UF2 file | | 28 | 4 | fileSize/familyID | File size or a unique ID for the target board family | | 32 | 476 | data | The actual firmware data, padded with zeros | | 508 | 4 | magicEnd | Final magic number, 0x0AB16F30 |
This powerful methodology unlocks the ability to analyze proprietary firmware, understand device behavior, recover lost source code logic, and find security vulnerabilities. The path to decompiling a UF2 file is not a single step but a journey through a powerful and rewarding reverse engineering landscape.
Understanding this two-step process is essential for anyone hoping to recover or analyze the logic within a UF2 firmware file. While the journey from a UF2 file to readable source code is complex and not always successful, the path is well-established with powerful tools waiting to be used. uf2 decompiler
For ARM Cortex-M architectures, the Vector Table sits at the very beginning of the mapped flash memory address:
This is an open-source Python tool set designed to pack and unpack UF2 files. It is the closest tool to a universal "decompiler" for UF2 containers. | Offset | Size | Field | Description
Most UF2-compatible chips utilize an architecture (Thumb-2 instruction set). Step 3: Loading the Binary into a Decompiler
To effectively "decompile" a UF2 file, you should not look for a single "UF2 decompiler." Instead, the robust workflow involves two distinct steps: While the journey from a UF2 file to
Within each 512-byte block, only 256 bytes contain actual data or machine code. The remaining bytes are reserved for metadata, magic numbers, and flags.
The most fundamental tool for the job is uf2conv.py , a utility script originally from Microsoft's UF2 repository. It's the "Swiss Army knife" for performing the basic packing and unpacking operations.
uf2conv.py firmware.uf2 --output firmware.bin
Technically, you don't "decompile" a UF2 file directly. Decompilation is a two-step process: