Problem about USB HUB on RB751U(can not receive data )

RouterOS General
1

I have an application need to connect a USB hub to RB751U, there is a very wired issues as below:

  1. RB751U is connected to a usb hub;

2.Usb serial convertor is connected to usb hub;

3.RB751U is found the usb hub and usb serial convertor, and connect this convertor to a normal computer with serial.

  1. open a new terminal in winbox, and type /system serial-terminal usb1 channel=0

  2. open a hyper terminal on the computer.

6.the serial port of the computer can received any typing from RB751U, But the RB751U can not receive any typing from the computer.

For sure the RB751U can receive the typing from computer when the usb serial convertor is connected to RB751U directly.

Anyone have the same issues? Really appreciate for any help!