Why the serial port outputs garbled text?

Description

After my VisionFive is powered on, the serial port outputs some garbled text.

SoC

JH7100

SBC

VisionFive

Software

Fedora 33

Cause

  • The serial cable is not cross-connected.

  • The electrical level of the USB-to-serial port is wrong.

Procedure

  1. Check whether the serial port is connected correctly: confirm that the normal serial port is connected at 115,200 baud rate; if it's connected with debug port at 9,600 baud rate, the code cannot be displayed normally.

  2. Confirm that both ends of the serial port are connected tightly with a Dupont cable; if it is loose, reconnect it.

  3. Check the connection mode of the serial port. If the serial port is cross-connected, it is correct; if it is direct-connected, change to the cross-connection method.

  4. Check the VID and PID of the USB-to-serial master control. Confirm that the Prolific PL2303 can be used on VisionFive.

  5. Check the electrical level of the USB-to-serial port. Confirm that the electrical level of the USB-to-serial port is 3.3 V; if not, change the serial line with 3.3 V, and the serial port output will return to normal.