Defining Multicode Expression Notes - Motorola DS6878 Product Reference Manual

5 - 38 DS6878 Product Reference Guide
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
single-byte parameter numbers, extend the value to two bytes by adding 00 before the parameter number.

Defining Multicode Expression 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.
•
When defining regions:
• Defining a region much larger than the bar code improves tolerance to scan distance and angle, but can
cause a decode of a nearby bar code instead of the target bar code. Therefore, for best performance
define larger regions when only a few bar codes are in view and those in view are widely separated.
• Defining a region close to (or smaller than) the target bar code improves the probability of decoding this
bar code rather than one nearby, but scan distance and angle must be more accurate. Therefore, for best
performance define small regions when many bar codes are in view or those in view are close together.
•
Use Region elements to improve decode speeds by reducing the image area to search for the target bar
code.
•
Specifying Code Type may also improve decode speeds for some code types.
•
Although you can scan parameter bar codes when multicode mode is enabled, be aware of the following: If
the multicode expression defined a region(s), to scan a parameter bar code you must position the bar code
within the first region defined in the expression. In some cases, this first region is not the center of the image
and aiming at the parameter bar code does not result in a successful decode.
The following examples show the multicode expressions in both hex and decimal formats, however in the sample
figures the values are decimal. Be sure to use the correct base numbering system when creating an expression. A
region specified as 0x00 0x00 0x64 0x32 represents a region with coordinates of Top-Left (0,0) and Bottom Right
(100,50).
Chapter 15, Symbologies). For