Device controlling

Device calibration

The scanner device contains some factory generated device specific parameters called Calibration data. Reading the data from the device may take a long time, which consequently slows down the system startup. To save time the data file is automatically copied to the local file system at the first attempt of using the device.

The calibration file

The calibration file can be placed in one of the following three different directories where our system searches for the newest version of this file:

• A directory specified by the calib_path property.
• The
  • %CommonProgramFiles%\gx\pr directory on Windows systems,
  • /var/gx/pr directory on Linux systems.
• The
  • %SystemRoot%\system32\gx\pr directory on Windows systems,
  • /usr/share/gx/pr directory on Linux systems.

The exact path and filename of the used calibration file can be read from the calib_file property. The calibration file contains information about the device only and may be freely copied from a computer to another.

Between captures

Between two capturing processes the light and camera control modules are in a so called freerun mode. In this mode the system can run a set of the following tasks that the user can enable through the freerun_mode property:

• Presence test - for detecting user action at the beginning and at the end of the capturing process.
• Preview capture - low resolution real-time preview capturing.

The usable modes are defined in the FPS_FREERUNMODE enumeration. Depending on the type of the device some tasks cannot be combined.

Preview

To capture a real-time preview image, the user can either call the CapturePreview function or handle the preview related events (see Event handling). To view the captured image, the image display function is to be called with FPS_IT_PREVIEW image type. The preview light control works only if freerun mode is set properly.

Controlling the device

The devices can have status leds and buttons which are fully controllable by the user through the SetStatusLed, TestButton and GetButtonEvent functions, except the power led available on some devices. The devices can report their power state (see Event handling) or it can be queried using the TestPowerState or TestPowerLevel functions.

Storing user defined data in the device

There is the possibility of storing user data in the internal memory of the device. The size of the enabled free space can vary between different types of devices. It can be used for example to store user defined serial number, legacy information or other general information restricted to the device.

User data space access is on block level, using device dependent fixed-size blocks. One can use the GetUDInfo function to get general information about the user data space - the size of one block and the number of available blocks. The first block index and the number of blocks to use must be defined at each user data read or write.

Note:

As the number of writes of an EEPROM chip is limited, please use this feature carefully.