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Before flashing a kernel or verifying a boot, you need two physical connections to your Qualcomm® Linux development kit: a USB connection for fastboot and ADB, and a serial console connection for early-boot log capture.

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Required hardware

ItemPurpose
USB-C cableFastboot flashing and ADB access
USB-to-serial adapter (3.3 V UART)Serial console for early-boot output
Host machine running Ubuntu 22.04Confirmed by Prerequisites & host setup

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Set up the serial console

The Qualcomm® Linux development kits expose a debug UART over a USB-to-serial adapter. The serial console is the primary channel for inspecting early-boot messages, kernel panics, and U-Boot/UEFI output before the network stack is available.

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Install a terminal emulator

sudo apt install minicom

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Connect the USB-to-serial adapter

Plug the adapter into the host and identify the device node: 
ls /dev/ttyUSB*
# or, for CP210x/CH340 adapters:
ls /dev/ttyACM*
Add your user to the dialout group if permission is denied: 
sudo usermod -aG dialout $USER
newgrp dialout

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Open the serial console

Qualcomm Linux development kits use 115200 baud, 8N1, no hardware flow control: 
minicom -D /dev/ttyUSB0 -b 115200
To exit minicom, press Ctrl-A then X. To disable hardware flow control, open minicom settings with Ctrl-A O → Serial port setup and set Hardware Flow Control to No.
Alternatively, use picocom: 
sudo apt install picocom
picocom -b 115200 /dev/ttyUSB0
For board-specific UART pin assignments and adapter wiring, refer to the hardware documentation for your development kit.

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Set up fastboot and ADB

Fastboot is used to flash kernel images; ADB provides shell access after the device has booted.

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Install platform tools

sudo apt install android-tools-fastboot android-tools-adb

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Enter fastboot mode

After powering on the device, select Volume Down. The serial console shows: 
Fastboot mode...
The exact button combination varies by board. Refer to your development kit’s hardware documentation if the above does not work.

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Verify fastboot connectivity

fastboot devices
Expected output (the serial number varies by board): 
1234567890abcdef  fastboot
If no device appears, check the USB cable, confirm the device is in fastboot mode, and verify USB permissions: 
# Add a udev rule if fastboot requires sudo
echo 'SUBSYSTEM=="usb", ATTR{idVendor}=="18d1", MODE="0666", GROUP="plugdev"' \
    | sudo tee /etc/udev/rules.d/51-android.rules
sudo udevadm control --reload-rules && sudo udevadm trigger

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Verify ADB connectivity (post-boot)

After the device has fully booted, ADB should enumerate over the same USB cable: 
adb devices
Expected output: 
List of devices attached
1234567890abcdef  device
Open a shell: 
adb shell

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Next steps

With serial console and fastboot confirmed, proceed to Install & boot the kernel to flash your build and verify the running kernel.