Communications Router

Both hardware and firmware for the router were designed and developed as part of a new product range. The new product range was required to interface to a third party system using the BACnet point to point protocol. The router was designed as a gateway and routing device to translate between the BACnet protocol and the company's proprietary field bus protocols. The router needed to support ARCNET and LON plug-in cards as well as three serial ports.

Introduction

The hardware for the router was based around the Phillips XA 16-bit processor, which provided enough processing power for the application.

The code space was provided by a FLASH memory device and allows the product to receive updated firmware from any of its communications ports. Battery backed RAM was provided to allow the device to store logged data which it retrieves from other networked devices. The firmware for the router was written in C and compiled to XA code.

The router was required to provide an interface to field-bus devices from the PC over a serial link (RS-232) or modem and to perform data logging and alarm monitoring of values available from other networked devices. We created the PC software that communicates with the router. For details, see the communications server. The networked devices could be on any port, running one of four possible protocols so the heart of the router contains a common protocol which is translated to whatever is running on its communications ports.

The router also contains a real time clock and broadcasts the time over its networks to keep the other devices synchronised with the current time.

This product has been in production since 1997 and now forms part of a very successful building management system that is sold worldwide.