Combining data with non-data characters #173
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Like other "non-data characters" There's more information about the purpose, encoding and effects on data transmission of the The barcode standards work within a framework that uses an abstraction of the interface between the reader and the host that models a unidirectional, wired connection that can transport byte values. This is referred to as the "byte channel" over which the "transfer protocol" is executed. In practise, a realisation of the interface may be anything from a RS232, keyboard wedge, various USB transports, ... each with their own limitations. It is the barcode reader solution provider's responsibility to relate each to the model interface so that the environment's messages "survive the channel". The following discusses how including standard ASCII characters such as HT within a barcode may not have the same effect when scanned as having actually pressed TAB on the keyboard depending upon the interface that is being used: https://stackoverflow.com/a/30904203/2568535 With regard to emulating a keypress such as F1 that bears no relation to an ASCII character, solution providers will often present a proprietary method by which to map certain data and non-data characters contained within the barcode message into emulated keyboard scan codes to be sent over a physical or virtual "keyboard wedge" interface. TL;DR; Barcodes contain bytes data. Read reader transfers the byte data into the host via one of several different interfaces, and go to various lengths to preserve the integrity of the byte data with regard to the limitations of the channel. They also may provide a proprietary means to "coerce" the byte data into things that may be useful to applications, such as special key-presses, but this is a feature peculiar to the reader and not the barcode symbol. |
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Like other "non-data characters"
^FNC3
is intended to be interpreted by readers (typically at the start of the message for reader programming purposes in this case) and is not ordinarily included directly in the data transmitted by the reader. It also bears no relation to the function key characters on a keyboard.There's more information about the purpose, encoding and effects on data transmission of the
FNCn
characters here: https://stackoverflow.com/a/31322815/2568535The barcode standards work within a framework that uses an abstraction of the interface between the reader and the host that models a unidirectional, wired connection that can transport byte values. This is referred to as…