Google unveiled Android 2.2, codenamed Froyo, at the Google I/O developer conference last week. The new version brings significant performance enhancements and a number of compelling new features. Google intends to roll out the new version to Nexus One users in over-the-air (OTA) updates over the next few weeks. Users who want to get their hands on the latest version right away, however, can manually update their handsets.
In a concise message published in the XDA Developer forum, well-known Android modder Cyanogen posted a link to Google's official Froyo update package—a compressed zip archive that can be manually installed on unmodified Nexus One devices.
Before you try to manually update, it's important to note that this update method is not officially endorsed by Google. The risk of bricking or similar undesirable outcome is minor, but still exists. Users who don't want to take any risks should wait for the OTA update. It's also important to note that this update method might not work on rooted devices and is not compatible with all Nexus One handsets.
The text "FRF50-from-ERE27" that appears in the zip filename tells you the build number of the updated version and the build number that you need to have on your phone in order to be able to use the update. Build FRF50 is the official Froyo release. ERE27 is an Eclair build that is on most of the Nexus One handsets that are compatible with T-Mobile's network frequencies.
The manual update using this specific zip file will work only if you are running build ERE27. You can see what build is on your phone by selecting the "About Phone" item in the settings menu. The build number will be listed at the bottom of the dialog. The AT&T-compatible N1 handsets are running on a more recent build (EPE54B) than the T-Mobile handsets and consequently cannot use the "FRF50-from-ERE27" zip file to update to Froyo. It's very likely that Google has an alternate update file for EPE54B users, but it just hasn't been found yet.
After you download the zip file, put it in the top level of the filesystem hierarchy on the SD card in your Nexus One and change the filename to update.zip. Turn off your phone and then turn it back on, but hold down the volume down button when you hit the power button. This will take you to a screen with a simple menu and three Android mascot characters on skateboards. Use the volume buttons to navigate to the "RECOVERY" item on the menu, and then hit the power button. The phone will start to reboot again, but it will display a screen with an exclamation point icon instead of booting all the way.
When you see the exclamation point, press and hold the volume up button and the power button at the same time. This will cause the phone to display the system recovery interface. It might get stuck at the exclamation point screen, in which case you just need to reset and try again. It sometimes takes two or three attempts. At the recovery menu, use the volume buttons to navigate to the "apply sdcard:update.zip" item. Hit the Nexus One scrollball to select the menu item and start the update.
When you start the update, you will see a progress bar as the update package is decompressed and analyzed. If you are not running a compatible build, you will see an "assert failed" error, and the update will abort. When it finishes, you can select the "reboot" option from the menu to start the phone up normally. If the update was successful, you will have tasty Froyo on your Nexus One.
