Can't connect to pixhawk4 from system console

#1

I follow the https://dev.px4.io/en/debug/system_console.html
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and want to connect to system console
Connect to the fmu debug port using usb2serial cable

and set putty like below, when power on pixhawk4 ,I can get some "!@#$!@#$!@#$@$@#$…"In the console
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image%20(1)
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I dont know it means what

Can anyone help me???

@elton-choi,do you have some advise?? Thanks s lot

#2

Is ground connected? Are you sure you’re using the correct COM port? You can check that by disconnecting whatever cable you’re using and checking if the port disappears.