Connecting to Yellow via serial console can be helpful for troubleshooting, e.g. to export a log.

1. On Windows, install PuTTY.
2. Open Device Manager.
   • Check if there is an entry under Ports.
   
3. Setup a USB connection: Yellow: USB-C, PC: USB Type-A.
4. The Device Manager should refresh and list a new entry under Ports.
   

   At the end of the entry, you see COM#. This is the port Yellow is using.

   
   
5. If the device doesn't appear in the Device Manager, check if the jumper JP1 is set to UART:
   1. Power off and unplug Yellow. Open the case.
   2. Make sure JP1 is set to UART.
   3. Close the case.
   4. Connect Yellow to your router again via Ethernet.
   5. Plug power back in.
6. Start PuTTY.

   

   • Under Connection type, select the Serial radio button.
   • Under Serial line, enter the port Yellow is using, e.g. COM3.
   • Under Speed, enter 115200.
   • If you want to use these settings later again, you can save the session.
7. Optional: Setup PuTTY logging.

   

   • Under Category, select Logging.
   • Select the Printable output radio button.
   • Under Log file name, enter the path and filename where you want the log files to be stored.
8. Start PuTTY session
   • To connect to the serial console, click Open.
   • Result: The serial console opens.

     

   • Typically, the console does not show anything on start up.
9. Hit the Enter key until prompted for credentials.
   • When homeassistant login: appears, enter root
   • No password is required. Hit the Enter key.
10. The console offers the Home Assistant CLI under the command ha. The command allows to get information about the state of the system. Typically useful commands are:
    • To print the supervisor logs, type
      ha supervisor logs
    • To print out the network info, type
      ha network info
11. To reboot Yellow
    • In PuTTY, enter reboot and press the Enter enter.
    • Result: The system reboots and you can observe the boot logs from start. If logging has been enabled, the boot process is also stored in the configured log file.

Resources:

Advanced Serial Console on Windows