A Universal Intelligent System-on-Chip Based Sensor Interface - Embedded.com

A Universal Intelligent System-on-Chip Based Sensor Interface

The need for real time, reliable, low maintenance distributed monitoring systems is becoming nowadays more and more obvious in several applications in the environmental, agro-food, medical, and industrial fields.

In this sense the growing interest in sensor network technologies and in sensor related technologies in general, is an important indicator of these new needs.Numerous transducers are available on the market with a multitude of different interfaces to provide measurements of all kinds.

Typical front-ends are voltage output, current output, capacitive or resistive outputs, and several digital interfaces such as RS232, I2C, SPI, frequency and bus based interfaces.

However, the presence of such a large number of different interfaces often makes the design and the realization of complex and/or distributed monitoring systems complex. Moreover, in order to design reliable and effective distributed monitoring systems, other fundamental aspects must be taken into account,such as the performance and the reliability of the sensors used for the system implementation.

To address these issues the concept of an intelligent sensor has come into being. It can be defined as a sensor with some kind of embedded intelligence (usually provided by a microcontroller), able to carry out advanced functions such as embedded signal conditioning, self-calibration, self-identification, diagnostic and networking activities. In order to achieve these advanced functionalities several smart interfaces for transducers have been recently proposed, often based on ASICs solutions.

Some commercial sensors show different degrees of “smartness”. However the standardization of the interfaces is still an open issue. An important effort in this direction was the introduction of the IEEE 1451 standard for intelligent sensors.

Nevertheless, at present, examples of intelligent sensors available on the market and compliant with this standard are still limited. To solve this problem, some dedicated hardware interfaces based on the IEEE 1451 standard, able to interface with different sensor typologies were recently proposed. These proposed devices are usually based on relatively complex dedicated electronic boards.

With this in mind, the authors propose a new low-cost system to convert a generic transducer into a intelligent sensor with multiple standardized wired interfaces. This innovative system is called Universal Intelligent Sensor Interface (UISI).

It provides a flexible analog and/or digital front-end (including conditioning and conversion functions), able to interface different transducer typologies, while providing enhanced processing and storage capabilities and a configurable multi-standard output interface (including plug-and-play interface inspired to IEEE 1451.3 standard).

The specific requirements of UISI devices in terms of flexibility, adaptability and functionalities can be achieved by using different technological solutions, depending on the expected performances and the costs.

The PSoC device used in the UISI is the 8051-based CY8C29466. It incorporates all the features that make possible the design of a UISI device in a single-chip: the internal analog and digital logic blocks are used to generate at run-time the front-end suitable for the generic transducer to be interfaced. The information for the front-end configuration is contained as a TEDS in the built-in flash memory, which can be re-written at run-time. The PSoC also provides resources to implement the communication with the NCAP or through auxiliary outputs.

The use of these devices makes possible the connection of analog and digital output sensors through the implementation of intelligent power management (based on programmable sensors power supply handling and microprocessor sleep mode) and the possibility of providing multi-standard external connections.

To read this external content in full, download the complete paper from the open on line archives at MDPI. 

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