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cannot find serial device

Question asked by Kai Wu on Nov 30, 2018
Latest reply on Dec 7, 2018 by Kai Wu
Recently, I connected a serial device to the NXP board, which is LS1012ARDB,  see the figure below.  

after plugging in the serial device to the NXP board, the output of dmesg[1]  is shown below
dmesg_ouput_nxp.png 
new USB device is detected but the serial device is not attached. Also, no new device name appeared 
under /dev. I tried to use minicom[2] to connect ttyS0, ttyS1....ttyS3, all of them failed, I got no
response from them.
But when I plugged in a usb stick into NXP board, see diagram below. The usb stick is successfully 
detected and attached, a new device name was created under /dev. 
 
Instead, I plugged the serial device to my laptop using USB to serial converter too. The diagram 
shows the connection
connection_laptop.png 
The output of dmesg after plugging the serial device on my laptop is shown below, the serial device is
 attached and I can access the serial device via minicom
dmesg_output_laptop.png 
It seems that the problem is happed because of the usb driver. The signal from switch console is not recognised by the NXP boardI am stuck on this problem. 
Any help or suggestions  will be much appreciated.  
[1]dmesg (display message or driver message) is a command on most Unix-like operating 
systems that prints the message buffer of the kernel. The output of this command typically 
contains the messages produced by the device drivers.
[2]minicom: Minicom is a text-based modem control and terminal emulation program for Unix-like 
operating systems.

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