KORG Monotribe AFSK firmware decoder

decoder.py

# -*- coding: utf-8 -*-
# KORG monotribe firmware decoder by:
# Ludovic Lacoste (aka Ludo6431) -- http://ludolacoste.com
#
# thanks to :
#   Th0mas @ http://gravitronic.blogspot.com/2011/12/decoding-korg-monotribe-firmware.html
#   nitro2k01 @ http://blog.gg8.se/wordpress/2011/12/04/korg-monotribe-firmware-20-analysis/


# decoder.py <input ascii bits file> <output file prefix>

import sys
from struct import pack

# input bits file (list of '0' and '1' in ascii (for example, produced by reader.py))
f = open(sys.argv[1], "r")
bits=iter(f.read())
f.close()

def readbyte(bits):
    byte=''
    for i in range(0,8):
        byte=bits.next()+byte

    return pack('B', int(byte, 2))

def waitsync(bits):
    i=0

    while bits.next()!='0':
        i=i+1

#    print 'wait: '+str(i)

def readpaquet(bits):
    paquet=''
    chk=0

    # read paquet header
    if readbyte(bits)!='\xA9':
        print 'problem, bad packet start'

    # read paquet data
    for i in range(0,256):
        by=readbyte(bits)
        paquet+=by
        chk+=ord(by)

    # read paquet footer
    paquet_type = readbyte(bits)
    paquet_type += readbyte(bits)
    paquet_type += readbyte(bits)
    if paquet_type!='\x55\x55\x55' and paquet_type!='\xff\xff\xff':
        print 'problem, bad paquet identifier'

    # read paquet checksum
    chk=chk%256
    if paquet_type[0]!='\xff' and chk!=ord(readbyte(bits)):
        print 'problem, bad checksum'

    return (paquet, paquet_type[0])

f=open(sys.argv[2]+'_header.bin', "wb") # 256B
waitsync(bits)
f.write(readpaquet(bits)[0])
f.close()

f=open(sys.argv[2]+'_fw.bin', "wb") # 32kiB
for i in range(0,128):
    waitsync(bits)
    f.write(readpaquet(bits)[0])
f.close()

f=open(sys.argv[2]+'_footer.bin', "wb") # 256B
waitsync(bits)
f.write(readpaquet(bits)[0])
f.close()

reader.py

# -*- coding: utf-8 -*-
# KORG monotribe wave firmware bit extractor by:
# Ludovic Lacoste (aka Ludo6431) -- http://ludolacoste.com
#
# thanks to :
#   Th0mas @ http://gravitronic.blogspot.com/2011/12/decoding-korg-monotribe-firmware.html
#   nitro2k01 @ http://blog.gg8.se/wordpress/2011/12/04/korg-monotribe-firmware-20-analysis/
#
# f1: ~4400Hz  (227µs)
# f0: ~2200Hz  (450µs)


# reader.py <input wav file> <output ascii bits file>

import sys, wave
from struct import unpack

# input .wav file
fd=wave.open(sys.argv[1], 'rb')

print 'nchannels:'+str(fd.getnchannels())
print 'sampwidth:'+str(fd.getsampwidth())
print 'framerate:'+str(fd.getframerate())

# thresholds of the software schmidt trigger
low=-3*32768/4
high=3*32767/4

# output ascii file (list of '0' and '1' in ascii)
f = open(sys.argv[2], "w")

st=0
pst=0
cmpt=0

fr=fd.readframes(1) # read one stereo frame (4 bytes)

while fr!='':
    v=unpack('h', fr[0:2])[0]   # get value of the first channel of the frame

    # get current state (schmidt trigger)
    if v>high:
        st=1    # high
    elif v<low:
        st=-1   # low

    if st>pst:  # raising edge
        if 5<cmpt and cmpt<15:  # high frequency
            f.write('1')
        elif 15<cmpt and cmpt<25:   # low frequency
            f.write('0')
        else:
            print 'Unknown cmpt: '+str(cmpt)

        cmpt=0
    else:
        cmpt=cmpt+1

    pst=st  # store previous state

    fr=fd.readframes(1) # read one stereo frame (4 bytes)

f.close()

fd.close()