Understanding Smart Sensors - Nomads.usp

Communications for Smart Sensors 125ProtocolBuilding/office automationEIbusCABGermanyCanadaHome automationX-10 X-10 Corp.Smart HouseSmart House L.P.CEBusEIALonTalkEchelon Corp.Michigan Parallel StandardUniversity of MichiganIntegrated Smart-Sensor Bus Delft University of TechnologyTime-triggered protocolUniversity of Wien, Austria (Automotive)DeviceNET is a trademark of Allen-Bradley Company, Inc. SDS is a trademark of Honeywell, Inc. LonTalk is atrademark of Echelon Corporation.specific manufacturers’ applications, as shown in Table 6.2. The Society ofAutomotive Engineers (SAE) has established SAE J1850 as the standard formultiplexing and data communications in U.S. automobiles. However, datacommunications for trucks and On-Board Diagnostics II (OBDII) are basedon the Controller Area Network (CAN) protocol developed by Robert BoschGmbH.The SAE Vehicle Network for Multiplexing and Data Communications(Multiplex) Committee has defined three classes of vehicle networks: class A,class B, and class C [6]. Class A is for low-speed applications such as body lighting.Class B is for data transfer between nodes to eliminate redundant sensorsand other system elements. Class C is for high-speed communications and datarates typically associated with real-time control systems. Table 6.3 summarizesthe data rates and latencies for the three classes.6.4.1 SAE J1850SAE J1850 was approved as the standard protocol for U.S. automakers in1994. J1850 defines the application, data link, and physical layers of the OSImodel. J1850 specifies two implementations: a PWM version and a variablepulse width (VPW) version. The differences are indicated in Table 6.4. SAE