Wiring the NI-9881
The NI-9881 has one 9-pin male D-Sub connector that provides connections to a
CAN bus. The NI-9881 has pins for CAN_H and CAN_L, to which you connect the CAN
bus signals. Connect these signals using twisted-pair cable.
The port has two common pins (COM) that are internally connected to the module’s
isolated reference and serve as the reference ground for CAN_H and CAN_L. You can
connect the CAN bus reference ground (sometimes referred to as CAN_V-) to one or
both COM pins. The port also has an optional shield pin, SHLD, that you can connect
to a shielded CAN cable. Connecting SHLD may improve signal integrity and EMC
performance in a noisy environment.
Caution
You must use a UL listed ITE power supply marked LPS with the
NI-9881.
The NI-9881 requires an external power supply of +9 to +30 V to operate. Supply
power to the NI-9881 V
SUP
pin.
Note
Power on V
SUP
is required for CANopen operation.
The NI-9881 pinout is listed in the table below.
The NI-9881 features software-selectable bus termination for High-Speed CAN
transceivers. On the NI-9881, you can enable 120 Ω termination resistors between
CAN_H and CAN_L through an API call. The Termination Resistor Specification
table lists recommended termination resistor values.
Figure 1. NI-9881 Pinout
Pin
Signal
1
No Connection (NC)
2
CAN_L
3
COM
© National Instruments
5
NI-9881 Getting Started
