Performing a Paperclip Loopback Test for Serial Port Communication

Paperclip Loopback Test

This test is to confirm whether you have two-way communication on your port.

How to test

Open FactoryWiz DNC

Select a machine

Click Terminal Mode

Unplug RS232 cable from the machine.  At the end you just unplugged, have someone hold a paperclip to pins 2 & 3 as shown in diagram, being careful not to touch the paperclip to the sides of connector.

Type a character in Terminal window.  You should see the character on the screen and also the same character in a different color next to it if two way communication is established. 


You can also perform this test at the port on a serial hub (Quatech, Comtrol or Moxa) or directly on the serial port of a computer (older computer models) or at the end of a USB to serial adapter for more modern computers that don’t have a native serial port.

If the connector is female you have to jumper pins 2 & 3 together by unfolding the paperclip and sticking each end in pin 2 and pin 3 and then performing the test above.  

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