Downgrade HTC Flyer 3G TW (HTC__621) to Gingerbread

The pain and suffering while downgrading HTC Flyer 3G of Taiwanese region back to android 2.3... Who knew it would be that hard?

Prelude to prelude

For a very long time I had HTC flyer as my main portable device. I didn't really like it, but still, it was overall joyful experience (without stylus, it was lost and found only this year). Since upgrade to honeycomb, it suffered from lags and I've been dreaming about returning to old gingerbread days for a while. Plus, bootloader had been unlocked by me at some point.

Prelude

I felt quite guilty for not backing up stock honeycomb firmware and because of that I've lost all the tablet functionality except hboot, fastboot and recovery. After a while, I found PIRA-FLY-ROM from dude on 4pda that let me bring my tablet to life. Still, it was not gingerbread, so I weren't in mood of finishing! And 4.0 was glitchy and overall weird, since it was ported from some newer htc phone. My tablet has HTC__621 cid - a very obscure one. That's why I have to use goldcard (In my case only non-HC sdcard worked) . Those of you who have Flyer of normal region just need to get fitting GB RUU.

Process

I would break it into those steps:

1. Use misc_version_flyer_3G.rar to edit misc partition's version number in custom recovery (see appendix 1)
2. Obtain goldcard.img using gcard.zip or website method and your favorite way to obtain SD CID
3. Paste contents of goldcard.img into beggining of SD card (dd if=goldcard.img of=/dev/sdX as an example)
4. Lock bootloader (Make sure you have Unlock_code.bin backups anywhere you can)
5. Rename rom.zip of GB RUU into PG41IMG.zip and place it on goldcard you've made
6. Boot into hboot
7. Wait for eternity
8. If it says "CID BAD!!!" your goldcard is invalid, go try another one. If not, do whatever you're being prompted to do.

Voilà, you have android 2.3 on your HTC Flyer!

Appendix 1: misc_version_flyer_3G usage

Extract misc_version_flyer_3G from supplied archive

1. adb devices
2. adb push misc_version_flyer_3G /data/local/tmp/misc_version_flyer_3G
3. adb shell chmod 777 /data/local/tmp/misc_version_flyer_3G
4. adb shell /data/local/tmp/misc_version_flyer_3G -s 2.00.405.3

Replace 2.00.405.3 with RUU version you want to downgrade to

Credits

• Wayne D. Hoxsie Jr. and B. Kerler for gcard.exe and gcx86
• piramida13 for cfw and 4pda articles
• globatron for article about downgrades on xda

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