Statistical Analysis of Time Delays in USB Type Sensor Interfaces on Windows-based Low Cost Controllers

Abstract

Real-time control systems need sensor data at periodic and predictable time intervals- this is one aspect of what is commonly called ""determinism"". Common forces that present challenges to determinism in Windows-based control systems are computer hardware, software, operating systems and external hardware interfaces. Popular, low cost interfaces that are deployed for attaching peripheral devices and sensors to computing platforms are Universal Serial Bus (USB) and Peripheral Component Interconnect (PCI).

This work examines the latency of such buses in Windows-based systems from a statistical perspective.Experimental evaluation reveals that PCI and USB offer different levels of performance. With the addition of more and more devices to any of these buses, overhead increases resulting in deterioration of determinism. This study looks at the issue of achieving predictability with a broader perspective of why and to what extent a real-time system is unpredictable.