National Instruments NI-9871 C Series Serial Interface Module

The National Instruments NI-9871 (Part Numbers: 779892-01, 779892-02, 779892-03) is a 4-Port RS485/RS422 Serial Interface Module designed to add serial communication capabilities to CompactRIO systems. The four independent ports on the NI-9871 operate in isolation from each other and from the CompactRIO chassis.

Each serial port features a 64-byte FIFO buffer that simplifies programming and conserves FPGA space. The NI-9871 is designed to be programmed using the LabVIEW FPGA Module, allowing direct FPGA-based control for precise communication timing and processing. The module does not support the LabVIEW Full Development System alone—it requires LabVIEW FPGA.

The NI-9871 is available in multiple versions: Part number 779892-02: Standard version (without conformal coating), Part number 779892-03: Conformal-coated version, providing additional protection against moisture and contaminants, Part number 779892-01: Includes four 10P10C-DE9 cables (1 meter each). This C Series Serial Interface Module supports a maximum baud rate of 3.6864 Mbps, features ±15 kV ESD protection on data lines, and allows cable lengths of up to 1.2 km (4,000 ft). The maximum power consumption is 3.5 W from an external power source (+8 to +28 VDC).

For electrical isolation, the NI-9871 offers 60 VDC continuous port-to-earth ground isolation and is tested to withstand up to 1,000 Vrms surge voltage. It connects to an external power supply via a four-position female pigtail connector. The four RS485/RS422 ports are fully electrically isolated from each other and other modules in the system.

The NI-9871 features RJ-50 connectors for serial communication, which are adaptable to DB-9 connectors via cables. This module weighs 5.4 oz and has an operating temperature range of –40 to 70 °C and a storage temperature range of –40 to 85 °C. It withstands vibrations of 5 grms (random) and 5 g (sinusoidal) at frequencies from 10 to 500 Hz.