For some reason, drone manufacturers seem insistent on us running the latest firmware on our drones.
None of them are keen on allowing you to choose which firmware version you want to run with.
Thankfully, the guys at https://drone-hacks.com worked out what was required in order to roll back to an earlier firmware version and this post aims to be a very easy to follow guide on how you can roll your Autel Evo II firmware back to any version you like.
No technical knowledge is required, it’s a very easy mod. If you can copy and paste some files to a MicroSD card, you’re in business.
I’ll start this guide with the caveat that when rolling back any firmware you should not skip a version. It might be a pain in the arse to get back to where you want to be, but you should roll back sequentially, version-by-version.
I was driven to write this guide due to the drifting issues that were introduced with the Evo 2 firmware v2.5.0 and while Autel have acknowledged the problem and are working on a fix, most of us can’t wait that long so this guide will show you how to roll back to the previous v2.3.3
The roll back principal is the same for any Evo 2 firmware version.
First up, before you do anything, you’ll need to download a few files.
The first file is the firmware version you want to roll back to (eg. v2.3.3) and the second file is a force_upgrade and the third file is a qiangzi_shengji file which is required to start the roll back process.
Both files, including every Evo 2 firmware version ever released, can be found here:
With your two files downloaded simply copy the firmware file to the root of your MicroSD card.
Then open the ZIP file and copy the force_upgrade and the qiangzi_shengji file to the root of your MicroSD card too.
Do not put these files inside any sub-folders and do not rename either of the files. You also must ensure no file-extension gets added to the force_upgrade or the qiangzi_shengji file as you extract it from the zip.
When done, the contents of your MicroSD card should simply look like this:
You may have other folders in there with your photos and videos as well and these are fine to leave in place, as long as these two files are in the root folder.
The force_upgrade file and the qiangzi_shengji file is the key ingredient here. If you only put an older firmware file on the card, the drone will see it’s an older version that the one currently installed and it’ll simply gloss over it and do nothing.
Both files on the card now?
That’s it, you’re ready to go.
To perform the forced firmware roll back, first ensure that your controller is not connected to your phone or tablet.
Turn the controller on.
With the controller powered up (and not connected to any devices) you can then put the MicroSD card in to the drone.
Now power on the drone.
The controller display will change to “Downloading firmware”.
Then it’ll quickly change to “Upgrading firmware”
Yes, it will say upgrading, even though it’s technically downgrading 
This stage will take about 7 minutes.
When done, the controller will briefly say “Checking”
With the checks complete it will then start to downgrade the firmware on the controller.
This is quite quick, taking just a minute or two:
When done, you’ll see the following message:
That’s it, you’re all done.
Simply turn off the drone and the controller, fire them back up and you’re good to go!
Some things to note…
During the downgrade process your Evo will reboot three or four times. This is perfectly normal. The lights on the drone will also change colour, and change sequence, at various stages of the process. Again, perfectly normal.
I recorded the downgrade process so you can see what the lights on the drone do, along with the various messages you’ll see on the controller:
The entire downgrade process will take around 12 minutes.
Any questions? Just ask 
