Perl script for D2 checksum calculation

[Dicky Dave]

Hi All,

I have knocked together a Perl script that calculates the checksum of the D2 firmware and prints it out, optionally creating a new version of the firmware file containing the calculated values. Thus, you would be able to start tweaking bytes here and there in the firmware and see what happens. I have not tried modifying anything yet because I do not have the D2 recovery drivers that are kicking around. So make modifications at your own risk.

I cannot take credit for working out the checksum algorithm as this is based entirely on the excellent work done by the Rockbox guys. Here is a thread with the details, http://www.rockbox.org/twiki/bin/vie.../TelechipsInfo.

I wrote it in Perl because I do not have a C compiler for Windows. I might post a C version soon but, while the Perl version takes a little longer, it only takes a few seconds to checksum the file. I had to put a .txt extension on it to upload it, so you will probably want to remove that. To run it, just do:

perl D2crc [--fix] <bin files>

Feedback/suggestions are welcome. Hopefully this is a first step to decompiling the firmware. I have given up hope that Cowon will fix the bugs and so have started plodding away trying to decompiling the firmware.