Recently, OnePlus One announced that its began to release Android-Lollipop based Cyanogen OS 12 OTA in select regions. OnePlus One also announced its release of its own Oxygen OS while CyanogenMod has unveiled BlissPop ROM update.
BlissPop ROM includes the latest Android 5.1 upgrades, and is based on original CyanogenMod source code. Users will receive the latest enhancements and bug-fixes through this unofficial BlissPop ROM.
Things to Note:
Confirm the device model number via Settings > About Phone (tutorial only for European OnePlus One phones). Install the correct OnePlus One USB driver (download), and install it on the PC. Data must be backed up, and the phone should have at least 80 percent charge.
Enable USB debugging: Settings > Developer Options (Android 4.0 or newer) or Settings > Applications > Development (Andorid 2.3 or earlier). The device should be rooted with Clockwork Mod (CWM) recovery and verify if the bootloader is unlocked.
Download Required files:
Android 5.1 BlissPop custom ROM
1. Download Android 5.1 BlissPop custom ROM to the PC. Connect OnePlus One smartphone via USB to the PC.
2. Copy BlissPop ROM .zip file to the root folder on SD card, and switch off the device. Boot the device into recovery mode by holding power and volume buttons simultaneously.
3. After entering CWM Recovery, clear data by tapping Wipe Data/Factory Reset. (use volume button to navigate, and power button to select an option)
4. Complete the ‘Wipe Cache Partition’ process, and go to ‘advanced’ option to perform ‘Wipe Dalvik Cache.’ (This prevents loop issues or any installation errors)
5. Return to recovery menu and tap Install zip from SD card. Select ‘Choose Zip from SD card,’ and select BlissPop ROM .zip file. Confirm the ROM to begin installation. (Follow the same step to install Google Apps)
6. Wait for the installation to complete, and tap ‘Reboot System Now’ in the Recovery menu.
The device might take a few minutes to start, to complete the booting process. Confirm the custom ROm installation via Settings > About Phone.