Archived:Perform Serial Loopback Test on COM2 Port of Touch Panel Computer

Updated Apr 3, 2023

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This content provides support for older products and technology, so you may notice outdated links or obsolete information about operating systems or other relevant products.



  • TPC-2212
  • TPC-2515
  • TPC-2206
  • TPC-2230

This tutorial shows how to set up a Touch Panel Computer for a serial loopback test to verify serial communication.

  1. Configure the COM2 port communication mode (RS-232, RS-422/485). The TPC-2230 can be configured through the SW2 jumpers. Legacy TPC models are configured in the BIOS. Refer to the user manual for your device for more information.

  1. Use the table below for the pin assignments based on the communication mode. For RS-232 communication, connect the transmit (TX) terminal to the receive (RX) terminal. For RS-422 communication, connect the TX and RX terminals of equal sign.
Note: See the user manual for your device for pinout details.
Communication ModePins
RS-232Pin 3 to 2 (TX to RX)
RS-422Pin 1 to 4 (TX- to RX-)
Pin 2 to 3 (TX+ to RX+)
RS-485Use RS-422*
*If the port is set to RS-485, the pins assignment shows a 2-wire mode for which a loopback test is not possible. Set the port to RS-422 and wire the pins required for RS-422 to successfully execute the loopback test.  
  1. Follow How to Perform a Serial Loopback Test to test the communication.