cannot find serial port after restart

The serial port can be recognized when the board runs from the sd card at the first time .

When I shutdown the linux by typing “sudo shutdown -P now”, the putty stops updating new lines.

The user1 led and user2 led still light on and never light off.

Then I try to plug out the USB OTG and USB Power cable, and plug in the two cables again to restart the board.

And this time the serial port never shows up in the list of the device manager on PC.

Is there any advice for this problem?

By the way ,how to configure the USB OTG port to be used only for communication without power supply.

Dear Customer,

We can directly connect the usb cable to OTG port for power supply and serial communication. if there is no inform on the serial again, please follow B. Connection via The UART port on <LINK_TEXT text=“ … reparation”></LINK_TEXT>. if both of them does not work, please try to burn the image again. thanks.

Seeed techsupport Team