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Introduction

Describes an alternative procedure to switch devices into EDL mode using UART. This procedure is only applicable if the device has a preloaded build. At a high level, the workflow includes the following:
  • Set up the host system with the required tools (UART console access)
  • Establish a UART connection to the device
  • Trigger the device to enter EDL mode using UART commands

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Install required packages

Minicom is a lightweight, terminal-based serial communication program used on Linux systems to interact with devices over a UART (serial) connection. It allows you to access the device’s console, view boot logs, and send commands directly to the system at a low level. Install Minicom on the host system: 
sudo apt install minicom

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Connect to a UART shell

  • To set up the debug UART connection and view the diagnostic messages, connect the micro-USB cable from the micro-USB port on the device to the Linux host.
    micro_usb_port
  • Check if the USB port is detected: 
    ls /dev/ttyUSB*
    Sample output
    /dev/ttyUSB0
  • Open Minicom: 
    sudo minicom -s
  • Use the Down arrow key to select the Serial port setup option. Use the Up and Down arrow keys to navigate through the menu. serial_port_setup
  • Set up the serial device configuration:
    • Select A on your keyboard to set up the serial device name such as /dev/ttyUSB0.
    • Select Enter to save the changes.
    • Select E on your keyboard to set the baud rate and 8N1 configuration:
      • Select the E key again if the baud rate isn’t set to 115200.
      • Select the Q key if the configuration isn’t set to 8N1. option_Q
    • Select Enter to save the changes.
    • Select F on your keyboard to set the Hardware Flow Control to No. serial_device_configuration
    • Select Enter to save the changes.
  • Select the Save setup as dfl option and then select Enter. save_setup_as_dfl
  • Select EXIT to open the UART console and then select Enter.
  • Sign in to the UART console:
    • Login: root
    • Password: oelinux123
If the sign in console doesn’t display as expected, verify the USB connection. If the issue persists, disconnect and then reconnect the micro-USB.

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Switch device to EDL mode

  • In the UART shell, move the device into 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)