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Design and Evaluation of a Real-Time Sensor Monitor System on Raspberry Pi using Xenomai
KTH, School of Electrical Engineering and Computer Science (EECS).
2019 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

A real-time system computes information before a deadline in a deterministic fashion.Xenomai is a real-time framework to port real-time industrial applications to Linux. Ithas a dual-kernel architecture, with one kernel dedicated to handling real-time tasksexclusively. This co-kernel operates along with the Linux kernel in the same memoryspace.MIND Music Labs is a Stockholm-based music technology company that specializes inreal-time operating systems (RTOS) for audio applications. Its flagship product, the ELKOS, uses Xenomai to achieve real-time performance.The purpose of this research project is to design a real-time system with a Raspberry Pi 3Model B running Xenomai to monitor and control sensors connected to its Serial PeripheralInterface (SPI). To this end, a Xenomai system was configured to run on a RaspberryPi. Afterward, a Real-Time Driver Model (RTDM) SPI driver was tested. Several softwarelayers were built on top of it so that a large-scale C++ application could use the RTDM SPIdriver. An AVR microcontroller was connected to the Raspberry Pi through a General-Purpose Input/Output (GPIO) extension shield to emulate multiple sensor devices. Thisapplication is designed to provide flexible user control over these devices, without it beingnecessary to know the low-level details of the SPI interface or Xenomai. An evaluationapplication was written to test the system’s response times to external stimuli. These observationswere benchmarked against a standard Linux system.The results observed during this research project suggest that a Raspberry Pi runningXenomai may offer hard real-time guarantees to communicate data over SPI for frequenciesof up to 1 kHz, even when the system is under a heavy workload.Keywords: Real-time, Raspberry Pi, Xenomai, Real-time driver model, Serial peripheralinterface, General-purpose input/output pins.

Abstract [sv]

Ett realtidssystem beräknar information före en tidsfrist på ett deterministiskt sätt. Xenomaiär en realtids-framework för att porta industriella realtid applikationer till Linux.Den har en dubbelkärnarkitektur, med en kärna avsedd för att exklusivt hantera realtidsuppgifter.Den här kärnan verkar tillsammans med Linuxkärnan i samma minnesutrymme.MIND Music Labs är ett Stockholmsbaserat musikteknologiföretag som specialiserar sigpå realtidsoperativsystem (RTOS) för ljudapplikationer. Dess flaggskeppsprodukt, ELKOS, använder Xenomai för att uppnå realtidsprestanda.Syftet med detta forskningsprojekt är att designa ett realtidssystem med en Raspberry Pi3 Model B som kör Xenomai för att övervaka och kontrollera sensorer anslutna till dessSerial Peripheral Interface (SPI). För detta ändamål konfigurerades ett Xenomai-systemför att köras på en Raspberry Pi. Därefter testades ett Real-Time Driver Model (RTDM)SPI driver. Flera mjukvarulager byggdes ovanpå den så att en storskalig C++ -applikationkunde använda RTDM SPI drivern. En AVR-mikrokontroller var ansluten till RaspberryPi genom en General-Purpose Input/Output GPIO extension för att emulera multipla sensorenheter.Denna applikation är utformad för att ge flexibel användarkontroll över dessaenheter utan att det är nödvändigt att känna till lågnivådetaljer i SPI-gränssnittet ellerXenomai. En utvärderingsapplikation har skrivits för att testa systemets responstider påexterna stimuli. Dessa observationer jämfördes mot ett standard Linux-system.Resultaten som observerats under detta forskningsprojekt visar att en Raspberry Pi somkör Xenomai kan erbjuda hårda realtidsgarantier för att kommunicera data över SPI förfrekvenser upp till 1 kHz, även när systemet har en tung workload.Nyckelord: Realtid, Raspberry Pi, Xenomai, Realtidsdrivrutinmodell, Serial PeripheralInterface, General-purpose input/output pins.

Place, publisher, year, edition, pages
2019. , p. 46
Series
TRITA-EECS-EX ; 2019:635
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-266114OAI: oai:DiVA.org:kth-266114DiVA, id: diva2:1381368
Supervisors
Examiners
Available from: 2019-12-20 Created: 2019-12-20 Last updated: 2019-12-20Bibliographically approved

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