Development of an industrial communication interface for a temperature sensor

Abstract

Fieldbuses are the most common used communication systems in industrial applicalions. Nowadays there are a when little chanee in bus definitions are carried out. This lot of incompatible different salutions causing economic waste ~~ paper proposes the implementation of reconfigurable fieldbuses using reconfigurable devices like FPGA (Field Programable Gate Array) or PLD (Programmable Logic Device). To evaluate the viability of this solution, this work implements the PROFIBUS (Process Fieldbus) protocol in an Altera's FPGA to connect a temperature sensor to a PROFIBUS bus. The physical level of the protocol as well as the required services of the data link level have been implemented in the FPGA. I. INTRODUCT~ONThe goal of fieldbuses is the serial communication between primary elements of automatization (sensors, actuators) implementing control and measurement functions, and control and automatization elements of a higher level (PLCs, numeric control machines, etc.). The IEC (International Electrotechhical Commision) and the ISA (Instrument Society of America) define them as "a digital, serial, multidrop data bus for low-level communication of industrial control process and instrumentation devices like actuators, sensors and local controllers".The development of fieldbuses has been fueled by the increase of microprocessor controlled manufacturing processes.Among the reasons involved in the growth of fieldbuses are:The necessity of reducing the wiring of the installations.The increasing processing capacity (intelligence) of sensors and actuators. The necessity of dispose of control equipment with standard connections. The increased integration of manufacture data into the enterprise information systems. a The tendency to use distributed process systems. Fieldbuses are placed in lowest level of communications networks (Fig. I). They respond to the following requirements:-Reduction in equipment. Make easy the system reconfiguration. Low installation costs. Reducea transmission times.0 Intrinsic security in hazardous areas.Increased information flow and improvemment of transmitted signal. Fig. 1. Control hierarchy of a manufacturing syslem.The above features make them suitable for a wide range of applications, from industrial process (industry of automobile, food, metallurgy, water, gas, etc.) to CIM (Computer Integrated Manufacturing), intelligent buildings and office environments, not only to increase life quality but also to implement better energy management [I].A fieldhus implements only three layers of the OS1 model: the physical, data link and application layers; and a layer for the management of the previous ones. Fieldbuses offer short messages (events, commands, etc.), with response times between 100 and 5 ms and great reliability (security in the communications) with throughputs lower than 1 Mbps and distances ranging from 200 m to 2 km. Usually, the physical medium is a pair wire with EIA RS-485 interface, although there are applications employing an optical fiber, coaxial cable, infrareds and even radio. ...

A Digitally Reconfigurable Sensor Interface for SOC using Delta-Sigma Modulators

“…The demand for system-on-a-chip (SOC) applications is rapidly growing and creating the necessity of tools able to increase the degree of design automation and prototyping of such systems. It is common to find mixed signal SOC applications that deal with low and high frequency signals and signal processing functions (linear and non-linear), for example sensors signal conditioning [1,2,3] and reconfigurable communication interfaces [4]. These signals must be conditioned, acquired and transmitted to a processor where the information will be processed.…”

“…Additionally, many times an field programmable gate array (FPGA) platform is chosen not only as SOC prototyping environment, but also as target final product carrier [1,4]. Mapping these mixed-signal applications to a SOC demands a wide range of specific analog or mixed signal processing blocks, such as analog amplifiers, analogto-digital converters (ADC), digital-to-analog converters (DAC), filters, mixers and other radio frequency (RF) modules [5].…”