Elo TouchSystems 1525L manual Language Overview, Properties

Section 1. Overview

usually remain unchanged, even though the new device may be very different from the old one.

The features of a driver that implement a device control language completely shield an application developer from the complexities of device-specific functionality.

LANGUAGE OVERVIEW

The device control language is text based and designed to utilize the read and write file I/O facilities of the underlying operating system. All commands, their responses and properties consist of text strings that are written to or read from the driver using basic file I/O. The control language is based on a property/command model that is similar to the notions of properties and methods as accepted in environments such as Visual Basic or Delphi.

Properties

All properties are accessed in a uniform way: by using a get (/get prop) or set(/set prop) command. Properties are either read/write or read only. A set command with a read only property will fail. All properties are identified by a string name and use strings for their arguments. Properties defined by the control language fall into the following three groups:

•Capability properties – These properties contain information about the capabilities of a particular device and are generally read only. They allow an application to query a device’s capabilities to determine if the device is suitable for a particular task. Included in this category are c_cardwpin, c_check, c_pin, and c_magnetic (e. g., /get c_check).

•Configuration properties – These properties configure a device for different modes of operation or may alter the way some commands behave. Because of this, they are usually readable and writable. They give an application the ability to set up a device for a particular task that requires a specific, non-default mode of operation. Included in this category are capitalize, dev_version, and port_name (e.g., /set capitalize 1).

•Device-specific properties −These properties cover configuration requirements that are not common among MagTek devices, even if the devices belong to the same class. An application can determine if a particular set of device-specific properties is available by first querying the device’s capabilities or version. Refer to Appendix D, Device Driver Summaries, for a particular driver to see how these properties are affected with an individual device.

Properties can be “action” properties. That is, the driver may execute an action on the device when a property is set. For example, an application can enable or disable magnetic stripe tracks by setting the trk_enable property. The driver responds by sending one or more commands to the device to enable or disable the desired tracks.

89