Connecting USB2Serial device to Arduino Due

Hi guys, I have a USB2Serial converter (RATOC rex-USB60f, to be specific) which connects to a RS232 distance sensor. My purpose is sending a command “M0” through Arduino to the RS232 device, and receive 8-bit returned data from the device on my Arduino serial.

My current attempts are:

  1. Connect the USB2Serial converter through native USB port
  2. Connect through a USB host shield

But none of them worked. Especially for the first method, when I connect the USB2Serial using a adapter cable, the power light on USB2Serial panel is still dim. Does anyone has any suggestions? Thanks a lot!

From: https://www.arduino.cc/en/Guide/ArduinoDue

The other USB port is the Programming port. It is connected to an ATMEL 16U2 which acts as a USB-to-Serial converter. This Programming port is the default for uploading sketches and communicating with the Arduino.
The USB-to-serial converter of the Programming port is connected to the first UART of the SAM3X. It's possible to communicate over this port using the "Serial" object in the Arduino programming language.