I have been using a T-Mobile G1 phone with new open source Android operating system for a while. It was a sort of “least evil” decision first, but later I started to like the phone. One the main reasons I changed my mind was the ability to flash other firmwares that the original. This is where the real power of open source comes in – you are free to change anything you want.

I haven’t time to play with the phone to create the environment to be able re-flash the firmware – particularly to create so called “Gold card” which enables you to store file on this SD card which will be used in the recovery mode as a source of new firmware. I approached one of the users of Android forum [czech only] to help with
this. Thanks and respect to Xsoft.

When I got everything to flash a new firmware a natural question appeared – which one to flash? You can find quite extensive overview of the firmwares in JAB ROM database. My experiences with the major ones are:

• Haykuro – Heavily modified with stuff from HTC meaning more features on one hand, but bugs, a lot of chineese on the other hand. Visually more flashy and coloured, but not as polished and clean.
• Jesus Freke – One of the first mods, the base for most other builds. Enough for everyone, visually clean and polished based on original Google user interface.
• The Dude’s – I used only version 1.2 and it is completely horrible visually with modified theme, icons and everything. Otherwise seemed allright.

I found two others which seemed to me OK – Cyanogen (a.k.a. “Jesus Freke on steroids” performance optimized, stripped to tha base) and TwistedUmbrella (Jesus Freke with ports of some HTC enhancements), but none of them has a important feature to me because of ability use GSM banking with my bank – SIM Toolkit application. They are both based on US version of Jesus Freke firmware which probably does not contain it in contrast to EU version.

So started hacking it … and here you have a simple guide how to create your customized firmware.

1. Get and unpack the base firmware you would like to modify.
2. Change the content of the directory structure as you wish (copy the apps into it in /system/apps, add media files into /media, …). The easiest way is to reuse other firmwares, but of course you can experiment much more.
3. Download and unpack SignApk application to be able sign the firmware package (private keys and certificate compatible with recovery image are included).
4. Delete the signature in /META-INF – files CERT.RSA, CERT.SF and MANIFEST.SF
5. Zip all the content in your structure into a your_firmware.zip file and put it into the directory where you unpacked SignApk.
6. Sign the zip file with SignApk: java -jar signapk.jar testkey.x509.pem testkey.pk8 your_firmware.zip your_firmware-signed.zip

Now you can proceed firmware flash with this signed file. If you do not want to get into here is my modified Cyanogen’s firmware version 3.4. Changes are:

• SIM Toolkit added
• MarketEnabler 3.0 beta added
• few media files from JF 1.51 (ringtones, notification etc.) added

Download it here: update-cm-3.4-mod_ch-signed.zip [46.8 MB].