DLSoft Application Note 04011

Function key emulation with barcodes

Most keyboard wedge barcode scanners will transmit 
function key codes when specific character combinations 
are scanned from a barcode. These combinations are 
scanner dependent and are beyond the control of dLSoft. 
Details of the combinations required should be in the 
barcode scanner's manual. 

These notes are a guide to the techniques used by the 
generic scanners we have used in-house.

For example, using Code 39 barcodes $A will normally 
transmit the F1 key, or using Code 128 the ASCII SOH 
(ASCII value 1) will transmit the F1 key.

For combination of the Shift, Alt or Ctrl key with 
other keys the situation is slightly more complex, 
in that the sequence:

<special key on> <other keys> <special key off>

is required.

For example using Code 39 barcodes the sequence 
%DF%E sends <Alt>F, or using Code 128 barcodes the 
sequence <RS>F<US> sends <Alt>F (where <RS> is ASCII 
value 30 and <US> is ASCII value 31).


While many of these functions are dependent on the 
barcode scanner in use, and details should be found in 
the scanner's manual, the following table shows some 
of the common codes in use.


Key		Code 39		Code 128	ASCII

F1		$A		SOH		1
F2		$B		STX		2
F3		$C		ETX		3
F4		$D		EOT		4
F5		$E		ENQ		5
F6		$F		ACK		6
F7		$G		BEL		7

<Ctrl on>	%B		FS		28
<Ctrl off>	%C		GS		29
<Alt on>	%D		RS		30
<Alt off>	%E		US		31


Most dLSoft barcode products enable ASCII values for 
non-printing characters to be used and details of the 
method of entry for these characters are given in the 
product's manual.

As an example for dBarcode-32, characters with ASCII values 
of less than 32 (the space character) many be entered by 
typing <alt>0xyz, where xyz is the three digit number 
obtained by adding 128 to the ASCII value. 

Note that this typing must use the numeric keypad - not 
the normal keys on a QWERTY keyboard.

So producing a barcode to represent <Alt>F requires the 
following characters:

<RS>F<US>

entered by typing

<Alt>0158 F <Alt>0159

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dLSoft
April 2001