trezor-firmware/bootloader/combine/prepare.py

#!/usr/bin/env python
from __future__ import print_function

bl = open('bl.bin').read()
fw = open('fw.bin').read()
combined = bl + fw[:256] + (32768-256)*'\x00' + fw[256:]

open('combined.bin', 'w').write(combined)

print('bootloader : %d bytes' % len(bl))
print('firmware   : %d bytes' % len(fw))
print('combined   : %d bytes' % len(combined))