Embedded Industry Trend – Sensors Get Smart

Publish Date: Oct 22, 2012 | 5 Ratings | 4.60 out of 5 | Print | Submit your review

Intake, compression, ignition, exhaust. If only the modern internal combustion engine was as simple as this four-stroke explanation.

Today’s engines are complex control systems that use embedded sensors for critical path feedback loops and performance and emission optimization. Besides the motor, modern vehicles contain hundreds of sensors in every system of the car, from parking assistance to tire pressure monitoring. Consumer electronics is another area teeming with embedded sensors. Microelectromechanical system (MEMS) accelerometers, for instance, have completely changed the way you interact with mobile phones and gaming systems and protect your hard drives from data loss when dropped. Last year, accelerometers alone boasted more than $2.4 billion USD in sales.

Pick your favorite phenomenon and there is probably a sensor for it, most likely an analog transducer. However, the current trend in embedded sensor technology is to shrink the entire acquisition chain – consisting of the transducer, amplifier, analog-to-digital converter (ADC), and a standard digital communication bus – down to one integrated circuit (IC). Although analog sensors will continue to be prevalent, this new trend toward digital sensors reduces cost, component count, and development time for integrating measurements into an embedded system.

National Instruments is making integration of digital sensors into embedded systems based on the NI reconfigurable I/O (RIO) platform more efficient. Collaborating with silicon vendors, NI identifies key measurement categories, corresponding sensor ICs, prototyping solutions, and digital communication intellectual property (IP) needs. NI now offers, and continues to expand, LabVIEW FPGA IP instrument driver-like interfaces for digital sensors; higher-level sensor drivers for desktop PCs and real-time operating systems; prototyping solutions; and a circuit design suite, including layout tools, circuit models, and footprint files for deployment.

Figure 1. Many traditional sensor companies are supporting new versions of their existing sensor platforms with digital interfaces for embedded applications.

1. Taking Advantage of Embedded Sensors

Unfortunately, there is no standard digital sensor communication bus. However, a survey of options reveals that Serial Peripheral Interface (SPI) and Inter-Integrated Circuit (I2C) buses cover most measurement types and sensor families.

1. Prototyping and Verifying on the Desktop – It is common to connect an embedded sensor to a PC for algorithm engineering and dynamic performance verification of a sensor. While NI provides PC-based data acquisition (DAQ) devices for measuring common analog sensors, it may not be obvious how to integrate a digital embedded sensor into a measurement and control system on a PC. Because most digital sensors communicate through serial communication protocols, use a device that translates those bus protocols to a standard PC bus, such as the NI USB-8451 SPI/I2C interface. This device includes a high-level device driver, making it easy to access both SPI and I2C devices. The USB-8451 abstracts away the physical bus layer, providing a simple read/write API, similar to instrument control buses such as GPIB and RS232/RS485. Most embedded sensors then respond to commands to read and write internal storage and configuration registers containing their latest digitized data.


Figure 2. The USB-8451 provides a simple LabVIEW interface to a wide range of SPI and I2C digital sensors, such as the TI TMP175 temperature IC used in thousands of refrigerated vending machines.

NI understands that most embedded sensors are provided at the IC level – not with prototyping-ready packaging and cabling – but the company is working with major digital sensor vendors to offer easier prototyping connectivity with little or no soldering and a path to volume system deployment with custom hardware design.

2. Deploying with NI Single-Board RIO – National Instruments is also making integrating digital sensors with FPGA-based RIO products easier by providing LabVIEW FPGA IP for SPI and I2C, specific sensor drivers, and circuit design resources for NI Multisim and Ultiboard software. You can download the low-level LabVIEW FPGA IP for SPI and I2C communication from the LabVIEW FPGA IPNet.

Additionally, if you consider SPI and I2C to be as common to embedded sensors as GPIB is to instrument control, it makes sense to build higher-level, sensor-specific drivers similar to the NI instrument driver network. On top of the low-level communication bus IP, NI has created high-level LabVIEW FPGA instrument driver APIs for several specific sensor families and accompanying real-time and desktop FPGA interface examples. Finally, to integrate these chip-level embedded sensors, NI offers circuit design resources such as specific Multisim symbols, Ultiboard footprints, and a reference design for NI Single-Board RIO custom daughter cards.

Figure 3. Connect to digital sensors with NI Single-Board RIO by downloading and integrating an SPI or I2C communication core from LabVIEW FPGA IPNet.

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2. Discovering New Embedded Solutions

Embedded digital sensor technology has lowered the cost and simplified the inclusion of measurement into an embedded system. The proliferation of these new sensors is evident in everything from automobiles to handheld devices. National Instruments continues to provide efficient embedded solutions and is now simplifying the integration of this technology from prototype to deployment.

Matt Spexarth   

Matt Spexarth is a product manager for NI Single-Board RIO at National Instruments. He holds a bachelor’s degree in electrical engineering from Kansas State University.

Rick Kuhlman   

Rick Kuhlman is a product manager for LabVIEW FPGA at National Instruments. He holds bachelor’s and master’s degrees in electrical engineering, as well as an MBA, from the University of Tennessee.

Download the embedded sensor e-kit with FPGA IP, embedded sensor drivers, and circuit design tools.

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This article first appeared in the Q2 2009 issue of Instrumentation Newsletter.

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