Attitude Heading Reference System (AHRS) SbRIO Interface

The Free Running Model Group of the Naval Surface Warfare Center presented PLF Consulting, LLC with the challenge to develop an interface to communicate with an LN-200 Attitude Heading Reference System (AHRS). The AHRS is manufactured by the Northrop Grumman Corporation. The interface to be designed had to be able to broadcast the data coming from the AHRS via UDP over a network or serially over an RS232 port in addition to allowing the user to set heading, latitude, and boresight axis rotations. The AHRS uses a simplified version of IBM’s synchronous data link control (simplified SDLC) over an RS485 interface with a slight twist in the fact it required additional lines that signal when to actually read and write data on the RS485 bus. The predecessor was a custom designed RS232 interface that was antiquated in both the hardware and software implementation and was in need of modernization. A major requirement was the ability to place the new interface inside a model and have a single connection via an off-the-shelf network cable or even a wireless device was extremely attractive. The predecessor could not be installed in a module due to size limitations so cabling between the model containing the AHRS and the RS22 interface was a major limiting factor and source of complications.