[sdiy] Comparing two compiled hex files

[O Gillet]

Two hex files can appear to be totally different and yet describe the
same data to be written on the target device:
- The byte count per line can be different. File 1 will contain
records like "Write those 16 bytes at 0x008000, Write those 16 byte at
0x008010", File 2 will contain "Write those 8 bytes at 0x008000, Write
those 8 bytes at 0x008008".
- One file can contain padding - extras 0x00 or 0xff written to memory
locations that do not matter because the instruction pointer will
never reach them.

Try converting from hex to bin using objcopy.

In your particular case, I would also consider the hypothesis that the
two files have been generated using different compiler versions.