An implementation of IEEE 1451 NCAP for Internet access of serial port-based sensors

Abstract

A major inhibiting factor to the development of networked digital (smart) sensors is the lack of a single sensor network/bus standard. Over fifty networks are in common use and no single standard is likely to emerge in the near future. In response, a NIST-sponsored initiative has developed the IEEE 1451 sensor interface standard which can be considered a universal interface between digital sensors/actuators and the network interface/driver, together with a standard electronic data sheet format. To date there has been little implementation of the standard by the sensor industry, probably due to dissatisfaction with the specific hardware interface (10-line), the complex software features, and the unavailability of a compatible commercial network interface. The device being reported here is intended to address these problems. The IEEE 1451 compatible interface between the Internet/Ethernet and serial ports described here is related to a series of websensors (sensors with a direct Internet address) previously developed by Esensors. The interface is an IEEE 1451 Network Capable Application Processor (NCAP). The NCAP (EM04) connects to the Internet through Ethernet. Within the NCAP is a communication board capable of receiving and sending email using the standard TCP/IP format. A second board formats sensor data to/from the serial ports. The available serial formats are: RS232, RS485, TII, Microlan/1-wire, IEEE-1451.4, Esbus, and 12C. The connector is 25-pin type D connector. Three select pins (eg. 010 for TII) configure the interface to the desired port format (RS232 is default). The external Smart Transducer Interface Module (STIM) or digital sensor must be connected to the appropriate pins assigned to tit at serial format. Included are several versions (some non-standard or proposed) of the Transducer Electronic Data Sheet (TEDS). Only parts of the full IEEE 1451.2 software requirements have been implemented.