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FirmwareUpdater/README.md

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+# Firmware update from SD-card
+
+RockChip SoC based devices support firmware updates by booting from a specially prepared SD-card. The official way requires a Windows-based application from RockChip ("Create Upgrade Disk Tool", aka "SD Firmware Tool"), and a suitable device boot loader file. Using them, I've prepared such an SD-card for you.
+
+[`DX220FirmwareUpdater.zip`](https://github.com/Lurker00/DX220-Firmware-Add-on/releases/download/DX220FirmwareUpdater/DX220FirmwareUpdater.zip) archive contains ready to use SD-card image file with 4GB partition, to update firmware on iBasso DX220.
+
+## Prepare bootable SD-card
+You may use any SD-card with capacity of 4GB or more.
+
+**WARNING:** writing the SD-card image file erases all the data on the card! To restore the SD-card for normal use, please use [SD Memory Card Formatter](https://www.sdcard.org/downloads/formatter_4/), available for MacOS and Windows.
+
+You need to unzip the downloaded archive ([`DX220FirmwareUpdater.zip`](https://github.com/Lurker00/DX220-Firmware-Add-on/releases/download/DX220FirmwareUpdater/DX220FirmwareUpdater.zip)) and write the `DX220FirmwareUpdater.img` file directly to SD-card. Under Windows, [Win32 Disk Imager](https://sourceforge.net/projects/win32diskimager/) can be used. Under Linux and MacOS, [Etcher](https://en.wikipedia.org/wiki/Etcher_(software)) GUI application performs the task (see [below](#an-instruction-for-macos-users) for example). Experienced users may use [`dd` command](https://en.wikipedia.org/wiki/Dd_(Unix)) from console, though great caution is required!
+
+If all went right way, you should have SD-card labeled as `DX220UPDATE`, with the following content:
+* `sd_boot_config.config`
+* `sdupdate.img`
+* `rksdfw.tag`
+
+`sdupdate.img` is empty (0 bytes), and it is the placeholder for the real firmware update image file.
+
+## Update firmware
+
+**WARNING:** Firmware update from bootable SD card is performed only when DX220 is not connected to a power supply or USB port. Charge it before starting firmware update!
+
+You need firmware update image file. For Android Oreo, iBasso provides `update.img` in its download. My firmware releases, to be used with RockChip FactoryTool (*not* files to be used with rkflashtool!), contain compatible `.img` file as well.
+
+1. Rename required `.img` file to `sdupdate.img`.
+2. Copy resulting `sdupdate.img` to the prepared bootable SD-card, confirming to overwrite existing file.
+3. Safely remove (unmount) SD-card from the computer.
+4. Disconnect DX220 from a charger or USB port (if it is connected).
+5. If your DX220 boots to Mango, switch it to boot to Android.
+6. Turn DX220 off.
+7. Insert SD-card into DX220.
+8. Turn DX220 on.
+
+In a few seconds it should start updating the firmware. At the end, it will prompt you to remove the SD-card from the slot, and will continue update, then erase storages and boot the device.
+
+## Useful notes
+
+You may keep several firmware images on the bootable SD-card under different file names. Only the one named `sdupdate.img` is used for the firmware update.
+
+## An instruction for MacOS users
+
+Please refer to [DX200 instruction](https://github.com/Lurker00/DX200-Firmware-Add-on/blob/master/FirmwareUpdater/README.md) for more information and hints.