[Miscellaneous Android Development] droidzer1:
Below you will find a download for my modification of a ported Team Hovatek TWRP file as their TWRP did not support OTG. Thanks to Team Hovatek for making a nice porting tool. Unfortunately it took some days and late nights of work to get the ported TWRP to actually be useful as this phone needs OTG support to use TWRP.

When I recently got the Unihertz Atom I didn't realize that it had no micro SD card slot for an external SD card like the Unihertz Jelly Pro had. However it does have OTG support unlike the Jelly Pro but I could not find any TWRP versions for the Atom. So I found a TWRP porting tool from Hovatek and I was able to create a TWRP version but USELESS unfortunately as that version of TWRP did not have OTG support for the Atom.

To make matters worse that TWRP can't deal with the encrypted internal storage of the Atom so there was no way to do a backup of your system. It was possible to format data in TWRP and do a backup to it but upon reboot all that data was gone and reset by the Atom as an essentially new phone being setup for the first time.

I needed a way to modify the ported TWRP so it would recognize an OTG flash drive or USB flash with an OTG cable. I used Image Kitchen to disassemble the original Atom Recovery image and also the modded TWRP recovery image so I could find what was missing from TWRP that was there in the original setup. After a whole lot of reassembling and reflashing various attempts to fix the OTG problem I finally got it. Had to add different lines of code to 3 different files within the unpacked TWRP recovery for it to finally recognize an OTG attached flash drive.

A couple notes on using your external flash drive with TWRP. First you want to insert the flash drive with an appropriate USB type C OTG adapter or cable. Or I see Sandisk (and possibly other brands) are now making a flash drive with USB and Type C dual setup for OTG use.

Bootup your regular phones Android system and look in the pull down notifications - it will ask if you want to use the flash drive as storage. Answer yes and it will then Format it to FAT32 0x0C type which is different than what it was fresh out of the package as most will be FAT32 0x0B type. Once formatted the way the Atom wants it you can use it. However if you put the drive back in your Windows computer it may not see the drive at all. The solution is to open Windows Disk Management and Assign it a drive letter. Once that is done you can read and write to it from both Android and Windows or Linux.

Once that is done you can turn off your phone (IMPORTANT). Do not use any apps that reboot into recovery after installing this TWRP or you will likely just get a black screen and it won't boot up until you reflash the preloader, boot and recovery.

To get into recovery hold down the Volume UP button and the Power button at the same time until you see Unihertz then release both. This is of course after you have flashed TWRP. More on that below. Once your are in TWRP you may have to remove your Flash drive if you had it plugged in during recovery boot up - then reinsert it for TWRP to see it. You can then see it when you mount storage or select storage and it should show the size of your flash drive.

You can then backup your Boot, Recovery, EMMC, System and cache. However the data on the Atom seems to be encrypted in a way that this TWRP does not see it so it will be best to use something like Titanium backup for your Apps and their data. The TWRP though will ensure a complete backup of your system and it's settings as well as the other items mentioned above. I am still looking into why it can't see the encrypted data part of the phone but for now it's nice to have an image of all the rest of the phone. If anyone can help with that I would appreciate it. So far I've tried several 'no encrypt scripts' and ones to turn off DM verity I found on XDA but none of them worked on this phone.

Here is the download of my modded TWRP and also a link for the SHA-256 of it:

TWRP mod: TWRP mod by droidzer1

SHA-256 for file above: SHA-256 for TWRP mod Love the Atom - fast Octacore 4GB Ram - 64GB Internal storage, rugged and tiny as an underfed mouse. :silly: Enjoy !