Home > Uncategorized > Treo 680 ROM hacking 2

Treo 680 ROM hacking 2

Palms ROM updates :

Palm have released several different methods of updating flash ROMs and firmware and recently they seem to have settled on using a method of splitting the large PalmOS ROM into small 2MB chunks to allow easy hotsyncing. These ‘hacksplit’ chunks are then combined during the flashing of the ROM image.

Fortunately for us, Matt at grack.com and a few others created RomTool for the Treo650. This was aware of hacksplit and could perform the somewhat trivial concatenation to allow us to extract and then edit the whole ROM image. It can also talk to the 650’s bootloader, which the 680 doesn’t have.

The only way so far to flash a custom ROM to the 680 is to use the release for updating AT&T branded phones, which included the ROM image in hacksplit format. We therefore need a method of converting our large monolithic ROM into hacksplit format and producing a valid MD5 checksum for it.

There is existing code to perform at least part of this work for the Tungsten TX, and I have modified it to work for the somewhat larger 680 ROM. [TXupdate original] [TXupdate_modified_for_680].

How to build a custom ROM :

1) Take apart the AT&T Rom with Romtool.

Extract it to a directory and replace the files you want. I listed files suitable for removing here.

2) Compress that same directory with Romtool to create low-palmos.zip and accompanying .md5 checksum.

3) Use the TXupdate REXX code I updated to split the large low-palmos.zip file into the HACKSPLIT sections that the ROM Updater expects (a.zip.pdb, b.zip.pdb, etc). i.e.

Put the large low-palmos.zip, and rexx32.exe and zip2pdb.rex into c:\scratch.

   cd c:\scratch
    c:\scratch\rexx32.exe zip2pdb.rex
    Write file low-palmos.zip.a.pdb
    ................................................................................
    Write file low-palmos.zip.b.pdb
    ................................................................................
    Write file low-palmos.zip.c.pdb
    ................................................................................
    Write file low-palmos.zip.d.pdb
    ................................................................................
    Write file low-palmos.zip.e.pdb
    ................................................................................
    Write file low-palmos.zip.f.pdb
    ................................................................................

4) Place those newly created ROM sections into the Rom Updater directory.

5) Recreate the MD5 checksum to match.

Do this with a hex editor, open the md5 checksum file you got from RomTool, copy the 32 character string and replace it for the one in low-palmos.zip.md5.pdb in the Rom Updater directory.

6) You can now copy the RomUpdater.prc and all the ROM files to the launcher directory on your SD card and run from there.

If you are after custom ROM’s and don’t want to make one yourself, there’s a thread on TreoCentral.

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