Digitizers do not make part of such standard peripheral devices as a mouse or a printer, for example. As a result, methods of connection of digitizers and protocols of receiving data were not standardized at the initial stage of using digitizers. Manufacturers supplied a program driver for every digitizer model produced which made it possible for application programs to use the set of functions realized by the hardware. The application was responsible for correct configuring of the digitizer and especially for indicating parameters of connecting the digitizer to the computer.
An important step forward in simplification of working with digitizers was development of WinTab standard made by a group of manufacturers. It provided the same interface for using different models of digitizers for programs working in Windows. The presence of WinTab driver for a particular model reduces the number of settings the application program should perform to the minimum.
Installing of digitizer driver in the Windows system is performed in accordance with documentation supplied together with the digitizer. The present subsection describes only configuring of a digitizer which should be performed by ObjectLand tools after the driver has been installed.
Configuring begins with pushing the button Configure in the pane Configuration of the dialog box “Digitizer adjustment”. It starts the work of configuring wizard the first page of which is shown at figure 21-2.
Figure 21-2. Wizard of configuring digitizer, step 1
The notion of digitizer configuration includes the type of digitizer and a set of parameters that determine the working mode of the digitizer and the mode of its connection with the computer. ObjectLand allows determining several different configurations on the basis of one digitizer type.
In the main pane of the page a list of digitizer types known to ObjectLand is given. This list contains several most popular models (base types) and can be supplemented by the user.
WinTab is one of basic types. In fact, WinTab drivers are supplied with different digitizer types, however, for ObjectLand user the differences between them are hidden by the standard WinTab interface. Other types in the list describe digitizers controlled by non-standard (not WinTab) drivers.
To add a new digitizer type to the list it is required to push the button New and enter in the opened dialog box “Digitizer type” (figure 21-3) a name of digitizer (an arbitrary string) and codes of three commands which ObjectLand sends to the digitizer in the course of work.
Figure 21-3. Dialog box “Digitizer type”
Digitizer command consists of one or several bytes which can be specified in documentation on digitizers either by their numeric codes or in the form of alphanumeric characters. ObjectLand provides the user with a possibility to specify bytes of commands either in numeric or in alphanumeric form accordingly. Each byte can be specified in the form of a character placed in angle brackets or in the form of a decimal number from 0 to 255, or in the form of a hexadecimal number from 00H to FFH. When using the hexadecimal form, it is possible to use uppercase letters A, B, C, D, E, F as well as lowercase letters a, b, c, d, e, f. If the command consists of several bytes, they are separated by commas. For example, the sequence of codes 65, 66, 67 can be specified in any of the following forms: “65, 66, 67”, “41H, 42H, 43H”, “<A>, <B>, <C>” or “<A>, 42H, 67”.
At the beginning of work with the digitizer ObjectLand sends initialization command and then a command of setting the remote mode. This digitizer mode denotes that packets of data on position and state of cursor are sent by the digitizer only as a response to the request from the computer. After setting the remote mode one more additional command which will be described below can be sent. After that in the course of working with the digitizer ObjectLand will periodically send the command of requesting the packet and receive response data.
Some digitizer types do not require special commands of initialization and setting of the mode. In this case the user leaves the corresponding fields empty.
After specifying digitizer name and determining three commands, adding of a new digitizer type is completed by pushing the button OK. The user can remove added types of digitizers from the list in future or change some name and command codes. Base types can be neither changed nor removed.
Not depending on whether one of base digitizer types or the type described by the user was selected, it is required to perform setting of a number of parameters before using the digitizer. When pushing the button Next, the configuring wizard moves to the step “Port setings”. The corresponding page is shown at figure 21-4.
Figure 21-4. Wizard of configuring digitizer, step 2
All parameters shown at this page refer to controlling exchange of data through a serial port of computer. Explanation of the meaning of parameters can be found in literature on computer hardware. Documentation on digitizers can contain requirements to admissible values of parameters of port settings.
When setting the WinTab driver the present page of the wizard contains only the message “Using of WinTab driver does not need a manual port setting.”
Next page of configuring wizard is shown at figure 21-5.
Figure 21-5. Wizard of configuring digitizer, step 3
Parameter of rate of receiving packets determines how often ObjectLand will send a request about the current position of digitizer cursor and about the state of its buttons. When the rate value is too high, it may cause problems, if the speed of digitizer work is not high enough. When the rate is low, an effect of moving of the editing cursor along the screen in discreet steps may appear. Default value (30 packets per second) is considered to be the most acceptable in most cases.
The packet type is chosen in accordance with documentation on the digitizer.
An additional command, provided it was specified, will be sent to the digitizer after commands of initialization and setting of remote mode. This command gives a possibility to select different characteristics of digitizer working mode, for example, to set required accuracy of tracking coordinates of digitizer cursor. A complete list of possible commands is given in documentation on concrete types of digitizers.
When setting the WinTab driver it is necessary to specify only the rate of receiving the packets, all other parameters are determined by the standard.
At next wizard step, which is the last one, the user can check the specified values of parameters and push the button Finish. For successful setting of configuration it is necessary that the digitizer was connected to the computer and was ready for work.
ObjectLand stores the current configuration of the digitizer and restores it in the course of further work sessions. The user can also store several different configurations having given arbitrary names to them. To do this it is required to push the button Save in the pane Configuration of the dialog box “Digitizer adjustment” shown at figure 21-6 and enter a name of the current configuration which should be saved. In this very dialog box one can remove configurations saved before which have become unnecessary.
Figure 21-6. Dialog box “Save”
Later on it will be possible to pass to the saved configuration by pushing the button Load and selecting the necessary name in the dialog box “Load”.
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