quoted

Just measure the voltage of your otg vbus pin.

Ok, I see it's 2.25 volts after I disconnect the microB-A thing . I
should see
0.8V constantly with nothing connected on the port?

You should see the voltage of vbus pin is less than 0.8v when
nothing is connected, we use B_SESSION_VALID (0.8v) to judge
it is connected or not.

You get 2.25 all the time or it is discharged very slowly?

Best regards,
Peter