Pins 7 and 8 are used for RTS/CTS hardware flow control where pins 4 and 6 are used for DTR/DSR hardware flow control. When using hardware flow control, you will need to connect pins 4 to 6 and 7 to 8 for RS-232. These connections can be seen in redbelow (figure 2 for RS-232 and figure 3 for RS-422/485). To perform a loopback test with no hardware flow control, you will need to connect pins 2 and 3 for RS-232 and pins 4 to 8 and 5 to 9 for RS-422/485. This connector is found on National Instrument’s one and two port serial interfaces.įigure 1: Pinout diagram for DE-9 Connector The DE-9 connector is the most common serial connector.
