Custom Communication Interface - DEF STAN 0018

 

 

Custom Communication Interface - DEF STAN 0018

 

Custom Communication Interface 

 

Introduction

This project was to provide a custom communication interface for a military aircraft Rolls Royce jet engine control unit. The interface in the Digital ECU is based on 70’s technology which needs to be supported for a significant number of years going forward. The existing hardware solution was obsolete and therefore in need of a supportable replacement.

Technical

DEF STAN 0018 shares a similar physical layer to 1553, Manchester Bi-Phase encoding, 1Mbps data rate, transformer coupled 78ohm terminated twinax cabling.
However there are major differences in the packet structure and bus architecture. 1553 has a master with multiple terminals responding to messages to their specific address transmitted by the master. DEF STAN 0018 allows the unit to continuously transmit housekeeping telemetry at a periodic rate with no commanding. Communication to the DECU must occur between the sync frame and the data frames. These differences prevent the use of a COTS 1553 board.

Solution

A custom 2U 19” rack mounted interface unit was designed to provide up to 4 asynchronous interfaces to 4 standalone DECU’s.

The communication interface was based upon National Instruments sbRIO 9601 hardware platform with two custom communica-tion interface PCBs providing the “1553” style electrical connections.

The custom designed PCB interfaces to the COTS FPGA board to provide the transformer coupled, Manchester Bi-Phase encoded physical data link.

Specific FPGA code, written in LabVIEW, de-codes the DEF STAN 0018 packets passing the data to the real-time processor via a FIFO. The real time layer buffers the data from the 4 DECU’s and passes the data to the Windows software layer where the data is streamed to disk and displayed for the operator on a simple Graphical User Interface

An Ethernet link and unit API was provided to give control and data capture  and logging from a Windows PC.

 

 

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