Motorola DS4208, Руководство по продукции

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4 - 26 DS4208 Digital Scanner Product Reference Guide
Multicode Expression Syntax: [n] [Element 1]; [Element 2 ]; ... [Element n];
Where n is the number of elements in the overall expression.
The multicode expression describes the bar code(s) that the digital scanner can expect to find in an image. Each
element represents one bar code in the digital scanner's field of view. The order of elements in the expression is
the order in which bar code data from each element transmits to the host. Elements are defined using one or more
of the following methods:
By Region
. This type of element limits decoding to a specific area within the digital scanner's field of view. Region
coordinates are defined as the top left and bottom right corners of the region, expressed in percentages of the field
of view. These can range from 0% to 100%, or 0x00 to 0x64 in hex, for both horizontal and vertical axes. A region
element is constructed as:
[R] [4] [Top, Left] [Bottom, Right]
Where:
•
[R] is the character R
•
[4] is 0x04, indicating there are four bytes thereafter to describe the region
•
[Top, Left] are two values representing the top left corner of the region
•
[Bottom, Right] are two values representing the bottom right corner of the region
By Code Type
. An element can specify a specific bar code symbology to find and decode somewhere in the field of
view. A code type element is constructed as:
[C] [2] [Code Type]
Where:
•
[C] is the character C
•
[2] is 0x02, indicating there are two bytes thereafter to describe the code type
•
[Code Type] is the desired symbology's parameter number (see Chapter 9, Symbologies ). For single-byte
parameter numbers, extend the value to two bytes by adding 00 before the parameter number.
Notes
When defining multicode expressions consider the following:
•
Use the Code Type specifier if there are bar codes of more than one code type in view.
•
Always use the Region specifier when there are multiple bar codes of the same code type.
•
When transmission order is important (the first element in the expression transmits first), use either type to
define the order.
•
When there are unwanted bar codes in view, filter them out in one of two ways:
• Use Code Type to specify only the target bar codes.
• Use Region to identify only the target bar codes.
•
If the expression does not contain a Region specifier, scanning angle and distance do not matter. If you
specify a region you must scan in a fixed orientation and at a fixed distance. Because of this, it is preferable
to use the Code Type specifier rather than the Region specifier.