SSATS: Sentinel Asset Tracking System

The SSATS system is a standalone local area asset tracking system. Each node in a SSATS system reports its location over a wireless link to the base station. The base station, bundled with the SSATS Desktop Application, allows a supervisor to continuously monitor the locations of all nodes in the network in real time. The SSATS system was built as a prototype system so consideration has not been given to hardware package design.



The SSATS hardware supports mesh networking technology so the number of nodes in your network increases the signal range beyond the capabilities of a point-to-point system. The SSATS network can in theory support up to sixty-four thousand nodes so it is expandable to any level of need.

The SSATS node hardware consists of three active components:

  • 48 MHz ARM LPC1114FN28 Microcontroller
  • XBee-PRO® 900HP Wireless Transceiver
  • USGlobalSat EM-506 48-Channel GPS Module

The base station consists of the same components except the microcontroller is an LPC1768 instead.

The GPS receiver obtains and provides the GPS information of the node to the microcontroller in standard NEMA format. This happens over a standard two wire serial connection at 4800 baud. The microcontroller parses the NEMA data and gets the important information ready to transmit to the universe. The formatted information is transferred over to the XBee-PRO® module over a high speed SPI connection. The XBee-PRO® module transmits the information to all nodes within range. From there mesh networking takes hold and routes the information through adjacent nodes, if required, to get the data to the base station. The last step in the process is for the base station module to transmit the data to the Sentinel Desktop Application and display it within the GUI. This repeats once every second for each node on the network!

Technical Specifications:

  • Wireless Frequency: 900 MHz
  • Maximum Point-To-Point Wireless Range: 305 m Indoors / 6.5 km Line of Sight
  • GPS Positional Accuracy: < 2.5 Meters
  • GPS First Fix Time: < 35 Seconds
  • MCU Clock Rate: 48 MHz
  • Power Input Requirements: 7.4-12V
  • Average Current Consumption: 100 mA

Sentinel Node and Base Station Software

Import programSentinel_NODE

The software that runs on the Sentinel nodes. This code is for the LPC1114FN28.

Import programSentinel_BASE

The software that runs on the Sentinel base station. This code is for the LPC1768.

Custom XBee SPI Library Used

Import libraryXBEE_900HP_SPI

This is an experimental driver for the XBee 900 HP pro module's SPI connection. This driver is unfinished and stability is not guaranteed. Use with caution.

Node Hardware

All parts can be seen in the below image of a node.


Desktop Application

800 The application code that runs the Sentinel Desktop Application is writen in C# and requires .NET Framework to operate. It displays a map on which icons are placed showing where each of the nodes on the network is located. A screenshot of the application is shown above.

Source code for the desktop application is available at:

Demo Program Video

This video shows the base station, in blue, and two nodes, in green, traveling about.


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