You can also use a simple paper clip to short the two connections by inserting the clip into each hole in the female connector, as shown below: The figure below shows the female DB-9 connector with pin# 2 and pin# 3 shorted. You need to insert one end of the cable into your serial port and use the other free end to make the loopback connection.
RS-232 DB-9 Connector The DB-9 connector is a 9-pin connector, as shown below. RS-232 DB-9 Connector RS-485 DB-9 Connector RS-232 DB-25 Connector RS-485 RJ-45 Connector Serial Cables Performing a Loopback Test with Windows HyperTerminal Follow the steps below to modify the appropriate cable. If you do not have a null-modem cable, or if you do not know which serial cable to purchase for your serial card, see the Serial Cables section below. To perform this test, you need to modify your null-modem serial cable temporarily so that the transmit and receive pins are connected. How to Do a Serial Loopback Test Overview A loopback test allows you to send and receive data from the same serial port to verify that the port is operational. Login or Create a user profile.ĭocument Type: Tutorial NI Supported: Yes Publish Date: Feb 18, 2008 How to Do a Serial Loopback Test- Developer Zone - National Instruments
