How to flash Samsung Galaxy S2 firmware

I flashed my Samsung Galaxy S2 twice. The first time was to try out a different firmware (2.3.3). That one went a little heart stopping initially, as my phone stopped flashing halfway, but in the end I was able to finish it on the second try. The second time I flashed, it was because I found the phone battery went down too fast for my comfort, so I wanted to see if a new version (2.3.5) was better in terms of battery usage.

You will need:
  • Firmware package for flashing
  • Odin to do the flashing
  • Samsung drivers (if you are having issues with "Gadget Serial" driver installation popups)

I followed the main instructions from here:

You can also download ODIN and the firmware you want from there. I shall be adding some extra comments to share the two experiences when I did this.

Get the latest "Gadget Serial" from the Samsung USB Driver for Mobile Phones:

Though I must mention the first time I tried this on my IBM laptop, the driver was not recognized and Windows still kept prompting me for the driver. I had to download a gazillion software (KIES, PC Studio, New PC Studio!!). Forgot which one worked in the end, but all of them are big downloads and even longer installations that was very frustrating when they did not work.

The second time though, I tried the USB drivers again on another XP computer and it recognized my S2 without any problems.

Back to the main flashing process. Before we begin, as always, I must put up this disclaimer - This guide is meant purely for educational purposes. If you follow it, I WILL NOT BE RESPONSIBLE FOR ANY DAMAGE TO YOUR PHONE!

The whole process should not take more than 5 mins (if everything went smoothly, that is)
  1. Shut off your S2 completely (phone should vibrate after screen goes black)

  2. Boot your phone into Download mode (Hold "Volume Down" + "Home" and press "Power")

  3. You should see a warning message appear.
    "Volume Down" to cancel the process (but that's not what you are here for right?)
    "Volume Up" to continue (that's what we want!)

    I should add here that during my first flash, the flash hang halfway and when I tried to go into Download mode again, this warning message briefly appeared and disappeared, and the screen went black and would not even boot up anymore (not unexpected, since the phone was already in process of flashing, so the old firmware on it was probably already half wiped off and not in a bootable mode anymore). I was worried that the phone had bricked!

    In the end, I had to do what I call "Fastest Fingers First". After pressing the 3 button combo, I got myself ready and when the warning screen came up, I quickly pressed "Volume Up". And it worked, I went into Download mode again and was able to finish the flashing on a second try! *Whew*

    So if something similar happened to you, don't get too worried first. Try to be faster with your fingers and see if you can get back into Download mode again.

  4. You should see the Android mascot appear on the center of the screen. On the top left hand corner, there should be "ODIN MODE" in red with some details of your phone.

  5. Back to your PC, open up ODIN the software. You should also extract the downloaded firmware too

  6. Click on "PDA" in ODIN and point to the firmware you just extracted. Check the box next to "PDA" too. "Auto Reboot" and "F. Reset Time" should be checked by default

  7. Plug in your phone now. The ID:COM area should become yellow as above

  8. Click "Start" and the process will begin. You will see the progress as below. Also, on your phone, there should be a blue bar below the Android mascot that will also show the progress.

    If for some reason, the progress took longer than 10-15 mins and seems to hang at a certain stage, then it is likely the flashing screwed up. I had my first time stopped at "boot.bin" stage. Your option now will be to carry on waiting indefinitely, or plug out the phone and restart (if you cannot power on/off using the power button, consider taking out the battery. But I stress again - I will not be liable for anything that goes wrong!!)

  9. When it shows PASS as above, you are done! The phone will now reboot and the rest of the process will take place on your phone. After which, the phone will reboot once more and you have your S2 with a new firmware loaded! Enjoy!


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