Nowadays, the builtin function HTA is available for this. No need to write your own.

AndreasKae

 

smiffy

Here you go. This converts a BYTE to its hex equivalent string.
It also has error checking in case you somehow manage to type a Hex value outside the range of 00 to FF (not sure how you could ).

FUNCTION_BLOCK HEX2STR

VAR_INPUT
HEX_VAL : BYTE;
END_VAR

VAR_OUTPUT
ASC_STR : STRING;
pASC AT ASC_STR : ARRAY [1..256] OF CHAR;
END_VAR

VAR
Digit : INT;
C : INT;
END_VAR

pASC[2] := INT_TO_CHAR(2);

Digit := BYTE_TO_INT(HEX_VAL) / 16;
IF (Digit <= 16) OR (Digit >= 0) THEN
IF Digit < 10 THEN
C := Digit + 48;
ELSE
C := Digit + 55;
END_IF;
pASC[3] := INT_TO_CHAR(C);
ELSE
ASC_STR := 'Invalid HEX character in string';
RETURN;
END_IF;

Digit := BYTE_TO_INT(HEX_VAL) - (Digit * 16);
IF (Digit <= 16) OR (Digit >= 0) THEN
IF Digit < 10 THEN
C := Digit + 48;
ELSE
C := Digit + 55;
END_IF;
pASC[4] := INT_TO_CHAR(C);
ELSE
ASC_STR := 'Invalid HEX character in string';
RETURN;
END_IF;


END_FUNCTION_BLOCK

 

If someone needs it in TIA

FUNCTION "HexToStr" : String
{ S7_Optimized_Access := 'TRUE' }
VERSION : 0.1
VAR_INPUT
HEX_VAL : Byte;
END_VAR

VAR_TEMP
Digit : Int;
C : Int;
t_HexToStr : String[2];
END_VAR


BEGIN

#Digit := BYTE_TO_INT(#HEX_VAL) / 16;
IF (#Digit <= 16) OR (#Digit >= 0) THEN
IF #Digit < 10 THEN
#C := #Digit + 48;
ELSE
#C := #Digit + 55;
END_IF;
#t_HexToStr:= INT_TO_CHAR(#C);
ELSE
#HexToStr := 'Invalid HEX character in string';
RETURN;
END_IF;

#Digit := BYTE_TO_INT(#HEX_VAL) - (#Digit * 16);
IF (#Digit <= 16) OR (#Digit >= 0) THEN
IF #Digit < 10 THEN
#C := #Digit + 48;
ELSE
#C := #Digit + 55;
END_IF;
#HexToStr := CONCAT(IN1:=#t_HexToStr, IN2:=INT_TO_CHAR(#C))  ;
ELSE
#HexToStr := 'Invalid HEX character in string';
RETURN;
END_IF;


END_FUNCTION