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adbd is disabled on the device by default and must be explicitly enabled before use.

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Introduction

Describes an alternative procedure to switch devices into EDL mode using ADB. This procedure is only applicable if the device has a preloaded image. At a high level, the workflow includes the following:
  • Set up the host system with required tools (QUD, ADB)
  • Connect device to ADB
  • Switch device to EDL mode

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Install required packages

QUD is required to ensure the host system can properly detect and communicate with the Qualcomm device over USB in Emergency Download (EDL) mode.
  • Clone the qud GitHub repository: 
    git clone https://github.com/quic/quic-usb-drivers.git
  • Ensure the install script is executable: 
    chmod +x quic-usb-drivers/QcDevDriver.sh
  • Install the QUD driver: 
    sudo ./quic-usb-drivers/QcDevDriver.sh install
ADB is used to communicate with a running device and is required to trigger a reboot into EDL mode from the operating system. It provides a convenient way to transition the device into the correct state for flashing without manual intervention.
  • Install adb on your host system using the system package manager: 
    sudo apt install android-tools-adb android-tools-fastboot
  • Verify if adb is installed on your system: 
    adb --version
    Sample output
    Android Debug Bridge version 1.0.39
Version 1:8.1.0+r23-5ubuntu2
  • The adbd service is disabled by default. A one-time setup is required to enable the service before adb can be used.
    • Connect to the device by following the Connect via UART guide.
    • Create the file /etc/usb-debugging-enabled to enable adbd. 
      touch /etc/usb-debugging-enabled
    • Configure the adbd service to start automatically. 
    systemctl enable --now android-tools-adbd

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Connect to ADB

  • Connect the device using the USB Type-C cable to the host computer.
  • Ensure that the device is recognized as a device by adb: 
    adb devices
    Sample output
    List of devices attached
68f592a device
  • Connect to an adb shell: 
    adb shell

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Switch device to EDL mode

  • In the adb shell, switch the device to EDL mode: 
    reboot edl
  • Verify if the device is in EDL mode: 
    lsusb
    Sample output
    Bus 002 Device 014: ID 05c6:9008 Qualcomm, Inc. Gobi Wireless Modem (QDL mode)