Chapter 1 Introduction

SmartSet Controllers and Features

AccuTouch E271-2210Serial Controller
AccuTouch E271-2201 PC-Bus Controller
IntelliTouch 2500S Serial Controller

Theory of Operation

The AccuTouch Touchscreen
The IntelliTouch Touchscreen

About This Manual


The SmartSet™ controller family is designed for use with Elo TouchSystems touchscreens. SmartSet controllers provide the drive signals for the touchscreen, convert the received analog signals into digital touch coordinates, and send them to the host computer. These controllers are the result of twenty years of experience in controller engineering at Elo.

SmartSet Controllers and Features

The following controllers make up the SmartSet controller family.

Features of SmartSet controllers include:

AccuTouch E271-2210 Serial Controller
AccuTouch E271-2201 PC-Bus Controller
IntelliTouch 2500S Serial Controller

Theory of Operation

Each SmartSet controller has the circuitry needed to interface an Elo touchscreen to a host computer. Functionally, the circuitry may be divided into the following categories:

The AccuTouch Touchscreen

Figure 1-1. AccuTouch Touchscreen

The logical sequence of operation for the SmartSet controller, used in combination with the AccuTouch touchscreen, is as follows:

  1. When the controller is waiting for a touch, the resistive layer of the touchscreen (the coating on the glass) is biased at +5V through all four drive lines, and the cover sheet is grounded through a high resistance. When the touchscreen is not being touched, the voltage on the cover sheet remains at zero. The voltage level of the cover sheet is continuously converted by the analog to digital converter (ADC) and monitored by the microprocessor on the controller. When the touchscreen is touched, the microprocessor detects the rise in the voltage of the cover sheet and begins coordinate conversion.
  2. The microprocessor places the X drive voltage on the touchscreen by applying +5V to Pins H and X and grounding Pins Y and L.
  3. An analog voltage proportional to the X (horizontal) position of the touch appears on the cover sheet at Pin S of the touchscreen connector. This voltage is then digitized by the ADC and subjected to an averaging algorithm, then stored for transmission to the host.

    The averaging algorithm reduces noise resulting from contact bounce during the making and breaking of contact with the touchscreen. Successive X samples are tested to determine that their values differ by no more than a certain range. If one or more samples fall outside this range, the samples are discarded and the process is restarted. This is continued until several successive X samples fall within the range. The average of these values is used as the X coordinate.

  4. Next, the microprocessor places the Y drive voltage on the touchscreen by applying +5V to Pins H and Y and grounding Pins X and L.
  5. An analog voltage proportional to the Y (vertical) position of the touch now appears on the cover sheet at Pin S of the touchscreen connector. This signal is converted and processed as described above for the X position.
  6. Successive coordinate pairs are sampled to eliminate the effects of noise. If a sample does not fall within an internal range, all X and Y coordinates are discarded and the X sequence is restarted at step 2.
  7. Once acceptable coordinates have been obtained, an average coordinate is determined and communicated to the host processor.

Parameters for the internal filtering algorithms can be adjusted through software setup. See Filter command.

The X and Y values are similar to Cartesian coordinates, with X increasing from left to right and Y increasing from bottom to top. These absolute coordinates are arbitrary and unscaled, and will vary slightly from unit to unit. The SmartSet controller can be calibrated to align the touchscreen coordinate system with the display image, reorient each axis, and scale the coordinates before they are transmitted to the host. Because of the stability of the AccuTouch system, recalibration is not necessary unless the position of the image changes.

The IntelliTouch Touchscreen

The IntelliTouch surface wave technology touchscreen consists of a glass panel molded to the precise shape of a display's face. It may be clear for best image clarity or treated for antiglare properties. Each axis of the touchscreen panel has a transmitting and receiving piezoelectric transducer, and sets of reflector stripes. See Figure 1-2, below, for details on the construction of an IntelliTouch touchscreen.

Other variations of the technology include SecureTouch™, where the glass panel is up to 12mm thick and thermally or chemically strengthened, and iTouch™ touch-on-tube technology, where the transducers and reflector stripes are placed directly on the CRT faceplate glass, eliminating the need for a glass overlay.

Surface wave energy is generated by the transmitting transducers mounted in the corners of the touchscreen. The touchscreen controller sends a 5.53 MHz electrical signal to the X-axis transmitting transducer which converts the signal into surface waves. A set of reflector stripes located on the lower edge of the glass reflects these waves across the active area of the glass. Reflector stripes at the top gather the reflected waves and direct them to the X-axis receiving transducer which reconverts the surface waves into an electrical signal.

Figure 1-2. IntelliTouch Touchscreen

About This Manual

This manual provides technical information on the Elo SmartSet touchscreen controller family. Details are given in this manual on the features, configurations, connections, and specifications of the SmartSet controllers.

This manual also includes examples of writing a software interface, such as a device driver, for the controller. Elo supplies a variety of drivers including its MonitorMouse® family of mouse emulation drivers for DOS, Microsoft Windows (3.x, NT, 95, 98, ME, 2000, XP, CE, etc.), OS/2, Macintosh, and Linux. Other third-party drivers and interfaces are also available. See www.elotouch.com or contact Elo before writing your own driver.

The SmartSet Companion Disk, which may be downloaded from www.elotouch.com, contains the sample driver source code and the SmartSet software setup utility, both described in this manual. See the !READ.ME! file, if present, for any changes or additions to this manual.

The rest of this manual is organized as follows:

Chapter 2 Explains how to set up the controllers via jumpers.

Chapter 3 Details the controller connections and installation procedures.

Chapter 4 Gives a tutorial on the important operating characteristics of the SmartSet controller interface using the SmartSet software setup utility.

Chapter 5 Describes the communication protocol for the controllers and provides the information you'll need for writing a software interface. Example C code is included.

Chapter 6 Provides a command reference for the SmartSet controller software interface.

Appendix A Details optional data output formats and emulation modes.

Appendix B Gives algorithms for coordinate scaling.

For more information on the AccuTouch or IntelliTouch product lines, including touchscreen and controller options, installation, and troubleshooting, see the AccuTouch Product Manual and IntelliTouch Product Manual respectively, available for download on www.elotouch.com.