1. A. Romano G.Lipari P.Pagano M.Chitnis
RETIS Lab
Real-Time Systems Laboratory
Resaerch Area: RTOS
Adopting the ERIKA Operating System to run Real-Time Application in WSN
A. Romano G.Lipari P.Pagano M.Chitnis

2. © 2007 Scuola Superiore Sant’Anna
Motivations
There is an increasing interest in Wireless Sensor Networks in fields like industry, medicine, automotive and military.
Typical applications are:
Surveillance
Medicine and health care
Vehicle traffic monitoring and control
Vibrational monitoring of building
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Problems
For WSN Applications demanding real time constraints, it is essential to have a Real-Time Operating System which :
provides Real-Time guarantees
supports WSN services
The most popular WSN Operating system is TinyOS that is well-known and widely-used.
Main features of tinyOS:
FCFS Task scheduling
Event triggered
Component based
TinyOS is not suitable for Real-Time Multi-tasking applications
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Main Idea
The basic idea consists of adopting ERIKA Operating System and a network stack protocol for a wsn node.
Porting of ERIKA to AVR ATmega128 hardware platform
Interfacing ATMEL IEEE Stack protocol with RT Kernel
Application Layer
Kernel Layer
Hardware Abstraction Layer
CPU Layer
MCU Layer
Board Layer
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5. Experimental setup (I)
The WSN node is composed by:
AVR ATmega128 microcontroller (8-bit CPU)
AT86RF230 transceiver
A star topology has been created:
4 DEVICE nodes
Make the association with the coordinator node
Send packets with CBR to the coordinator according to the IEEE standard
1 COORDINATOR node
Initializes the network
Associates all the devices requesting for association
Receive all packets arriving from the devices
Send all packets arrived through USB to the PC that collects datas
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6. Experimental setup (II)
AVR Atmel ATmega128
Atmel AT86RF230 Transceiver
expansion board Atmel STK501
development board Atmel STK500
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7. Experimental setup (III)
Device 3
Device 4
Coordinator
Device 2
Device 1
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Main results
In the coordinator node a task has been inserted with a variable execution length in order to simulate variable load.
In this way it’s possible to simulate the delay introduced by such node while receiving.
The delay has been simulated in two different scenario:
ERIKA with scheduling policy like tinyOS (all tasks have the same priority)
ERIKA with a Fixed Priority scheduling policy
In the last scenario we have experimented a strong decrease of delay confirming the results obtained by RTNS in a similar simulated scenario.
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Experimental results
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10. Conclusion and Outlook
The Porting of ERIKA for the hardware platform has been completed.
In ERIKA, an interface has been created to manage the services provided by the IEEE network stack protocol.
Work in progress:
Add primitives related to the Internetworking OSI layer to provide other important services like routing.
Differentiate the HAL to transmit data frames using different radio transceivers.
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11. E-mail: a.romano@sssup.it
Scuola Superiore Sant’Anna, CNR research area, Via Moruzzi 1, Pisa, Italy