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

© 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 2/11 © 2007 Scuola Superiore Sant’Anna

© 2007 Scuola Superiore Sant’Anna 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 3/11 © 2007 Scuola Superiore Sant’Anna

© 2007 Scuola Superiore Sant’Anna 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 802.15.4 Stack protocol with RT Kernel Application Layer Kernel Layer Hardware Abstraction Layer CPU Layer MCU Layer Board Layer 4/11 © 2007 Scuola Superiore Sant’Anna

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 802.15.4 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 5/11 © 2007 Scuola Superiore Sant’Anna

Experimental setup (II) AVR Atmel ATmega128 Atmel AT86RF230 Transceiver expansion board Atmel STK501 development board Atmel STK500 6/11 © 2007 Scuola Superiore Sant’Anna

Experimental setup (III) Device 3 Device 4 Coordinator Device 2 Device 1 7/11 © 2007 Scuola Superiore Sant’Anna

© 2007 Scuola Superiore Sant’Anna 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. 8/11 © 2007 Scuola Superiore Sant’Anna

© 2007 Scuola Superiore Sant’Anna Experimental results 9/11 © 2007 Scuola Superiore Sant’Anna

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 802.15.4 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. 10/11 © 2007 Scuola Superiore Sant’Anna

E-mail: a.romano@sssup.it Scuola Superiore Sant’Anna, CNR research area, Via Moruzzi 1, 56124 Pisa, Italy