Monday, December 25, 2017

[Tools, Tips & Tutorials] Entering EDL mode from fastboot mode

Thanks for this post emuzychenko

Some firmwares support rebooting to Emergency Download (EDL) mode in Android Bootloader aboot module (the "reboot-edl" command) but fastboot utility doesn't recognize "reboot-edl" in the command line and refuses to send the command to the device.

Since FastBoot protocol is simple and text-based, it is enough to send a packet containing "reboot-edl" text over USB. The simplest way to do that is to patch Windows fastboot.exe file, replacing "reboot-bootloader" text with "reboot-edl". As "reboot-bootloader" string is found in the command line, fastboot.exe sends the same constant string to the device. So if "reboot-bootloader" is replaced with "reboot-edl", you can specify "reboot-edl" in the command line and the same text will be sent to the device.

I occasionally locked bootloader in my officially unlocked/rooted Xiaomi Redmi Note 3 Pro (Snapdragon) so it could only boot to FastBoot or Diagnostic 900E modes. Tried to swich from 900E to 9008 with QPST but it reported unspecified error.

Analyzing aboot (emmc_appsboot.mbn) found that it supports "reboot-edl" so the only  thing remaining was to find a way to send it.

With patched fastboot.exe, successfully rebooted to EDL mode (9008) and re-flashed proper partition images.

Original post on XDA-Developers
Detailed guide on XDA-Developers

Therefore, to switch your half-bricked phone to EDL mode, you should do the following:


  • Download the attached ZIP archive and unpack it to an empty folder.
  • Boot the phone into FastBoot mode by holding both Volume Down and Power buttons until the bunny appears.
  • Connect the phone to the PC.
  • Double-click the "edl" (edl.cmd) file.
  • If the bunny disappears, your phone was rebooted and now should be in EDL mode (LED should flash red but not always).
  • Run MiFlash, wait 3-5 seconds and click "Refresh", COM port should appear in the list.
  • Proceed with MiFlash as described in the appropriate topics.

To check if this method can work for your device, open aboot image from FastBoot firmware file set (emmc_appsboot.mbn or similar file) in a hex viewer/editor and search for "reboot-edl" string.



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