Disclaimer
The absolute biggest disclaimer here. This is buggy as hell. This sometimes works, it sometimes doesn’t. If it doesn’t, don’t look to me for answers – I don’t have any. You shouldn’t be using an Android device to flash custom firmware, it’s a recipe for disaster. But if you have literally no other choice and want to try, here’s the steps.
Preparation
The very first thing you need is an Android device, of course and one with a USB-C connection. It can be a tablet, an Android handheld, a phone – doesn’t matter, just an Android device. You’re also going to need a branded SD card because we don’t do unbranded around here. Next up, to connect to the device, you’ll need a USB-C to USB-A adapter – they’re usually called OTG adapters and will connect right to the USB-C slot on your device. Lastly, you need an SD card reader – a USB-A one, and that will connect right into the OTG adapter.
Links to what you need:
Software wise, there are two that you’ll need. The first, is Solid Explorer File Manager from the Google Play Store and this will allow us to browse all of our files, but also to extract zipped files, which is how custom firmware is usually downloaded. Next, you’ll need an app called EtchDroid, and while it is on the Play Store, it’s for older versions of Android usually so the best way to get this is to go to the Github page, and download the APK from the latest release. EtchDroid is the equivalent of Rufus or Balena Etcher or any flashing program that you usually see on a computer, except on Android.
Grab your custom firmware
Connect the OTG adapter to your device, and then plug in the SD card reader and SD card as well.
Now this next step will depend on what handheld and what custom firmware you want to flash, but let’s say you have an muOS supported device and you want to put muOS on it. Head to the muOS website, and you want to download the latest release.
If you have an ArkOS supported device, same thing – head to the ArkOS website, find your device model and download the release for it.
And the list goes on. It really doesn’t matter what custom firmware, I’m just using these as examples.
Open Solid Explorer File Manager, browse to your Downloads folder or wherever that file downloaded, push and hold on the file, click the three dots, and select Extract. You’ll see a progress circle, wait till the green checkmark. When it’s done, it will have extracted the image file.
Flash your custom firmware
When it’s done, open EtchDroid, select Write an image, navigate to the extracted image file and select it. Make sure it’s the extracted one, you don’t want to select the zipped file as it won’t work. Select your SD card on the next page and then select start bottom right to begin the process.
This next part is important, but just make sure the device doesn’t go to sleep, the screen doesn’t turn off and all of that – keep the page open while it’s flashing the firmware to the SD card or it can corrupt the process and it’ll be a bad time for you.
If it does go to sleep, or turns off, feel free to try the SD card when it’s done and if you run into issues, just reflash following the same steps.
It’ll say write finished when that’s all done, and you can now go ahead and insert the SD card into your device, turn it on and set it all up.
You’ve flashed it, congratulations – what’s next?
You can now just continue following whatever guide you were following to setup the device – the only part of the usual guides I make that we just replaced, is the flashing of the image to the SD card – so the part I show involving Rufus. So if you don’t have a laptop, or computer and only have an Android device, you can follow all of these steps for any custom firmware guide to do it on your device instead.
Now, guides usually have you reconnecting after the first initial setup of a device, to add roms, or bios files, or add other files. You can follow the same steps of connecting the OTG adapter, the SD card and then open Solid Explorer and you can navigate to the files on that SD card using it.
From there, you can move, delete, or do anything you want with the files on the SD card. The world is your oyster.
Downsides
The one negative to all of this, or using an Android only device, is there’s no way to format a card as FAT32. So if there’s a operating system out there that wants you to format the SD card to that specific format to be used first, like Spruce for the Miyoo A30 for example, there’s no app for that on Android. Or alternatively, if you need to format an SD card as FAT32 to be used as the ROM SD card, in the second slot on most devices. For that scenario, you’ll still need a computer.
And there’s also the downside of none of this working, which happens a lot.
