WIP script to unpack Roli firmware files

roli_fw_extract.py

#!/usr/bin/python3

import math

import mido

FIRMWARE_IN = "firmware.syx"
FIRMWARE_OUT = "firmware.bin"

FIRMWARE_PUSH_COMMAND = 0x04

leftover_data = []


def demangle(data):
    """ Demangles data that's been encoded as 7-bit numbers. """

    input_data  = data[:]
    output_data = bytearray()


    while input_data:
        chunk = input_data[0:8]
        del input_data[0:8]

        # Typically, we get 7 bytes per 8, since we had 7 of 8 bits...
        resultant_size = math.floor(len(chunk) * 7 / 8)
        resultant_bits = resultant_size * 8

        # Convert the 7-bit chunks into one fewer eight bit chunks...
        septets         = [f"{i:07b}" for i in chunk]
        long_equivalent = "".join(septets)[0:resultant_bits]

        # ... and convert that back to bytes.
        raw = int(long_equivalent, 2)
        octets = raw.to_bytes(resultant_size, byteorder='big')

        output_data.extend(octets)


    print(len(output_data))
    return output_data


# Read the firware into memory.
roli_syx = mido.read_syx_file(FIRMWARE_IN)

# Prepare to write our output file.
output = open(FIRMWARE_OUT, "wb")


# Go through each message, and see what we have.
for message in roli_syx:
    data = list(message.data)

    # The first byte is already extracted for us, as it's SysEx standard.
    # The next four bytes are ID information and separator; throw those away.
    del data[0:4]

    # The _last_ byte is a checksum of the packet.
    # Discard it.
    del data[-1]

    # The next byte is the command.
    command = data.pop(0)

    # Skip non-firmware commands.
    if command not in [FIRMWARE_PUSH_COMMAND]:
        continue

    data_demangled = demangle(data)
    
    address = data_demangled[0:4]
    address = int.from_bytes(address, byteorder='little')
    del data_demangled[0:4]

    output.write(data_demangled)