Sonstiges 4 Bytes vom Wiegemodul in einer Hochsprache in Real-Wert konvertieren

FUNCTION "4ByteToReal" : Void
{ S7_Optimized_Access := 'TRUE' }
VERSION : 0.1
   VAR_INPUT 
      b0 : Byte;
      b1 : Byte;
      b2 : Byte;
      b3 : Byte;
   END_VAR

   VAR_OUTPUT 
      OUT : Real;
   END_VAR

   VAR_TEMP 
      iDWORD : DWord;
   END_VAR

BEGIN
      
    #iDWORD.%B0 := #b0;
    #iDWORD.%B1 := #b1;
    #iDWORD.%B2 := #b2;
    #iDWORD.%B3 := #b3;
    
    #OUT := DWORD_TO_REAL(#iDWORD);
    
    
END_FUNCTION

{
Es gibt Single(32Bit) und Double(64Bit) precision floats in https://de.wikipedia.org/wiki/IEEE_754

in C/C++:
float = 32Bit
double = 64Bit

in Simatic S7:
Real = 32Bit
LReal = 64Bit

in Delphi:
Single = 32Bit
Double = Real = 64Bit
}

Uses sysutils;
type
  TBytes4 = array[0..3] of Byte;
  
function bytes4_string(value_bytes: TBytes4): string;
var
  i: integer;
  result: string;
begin
  result := '';
  for i := 0 to sizeof(value_bytes)-1 do 
  begin
    result += Format('$%.2x',[value_bytes[i]]);
    if(i < sizeof(value_bytes)-1) then
    begin
      result += ' ';
    end;
  end;
  bytes4_string := result;
end;
  
function single_to_bytes4(value: Single): TBytes4;
var
  value_bytes: TBytes4 absolute value;
begin
  single_to_bytes4 := value_bytes;
end;

function bytes4_to_single(value_bytes: TBytes4): Single;
var
  result: Single absolute value_bytes;
begin
  bytes4_to_single := result;
end;

function reverse_bytes4(value_bytes: TBytes4): TBytes4;
var
  i: integer;
  result: TBytes4;
begin
  for i := 0 to sizeof(value_bytes)-1 do 
  begin
    result[i] := value_bytes[sizeof(value_bytes)-1-i];
  end;
  reverse_bytes4 := result;
end;
  
var
  value: Single;
  little_endian_value_bytes: TBytes4;
  big_endian_value_bytes: TBytes4;
begin
  // intern als Little Endian auf x86
  value := 123.4;
  writeln(Format('%.4f',[value])); // 123.4000
  little_endian_value_bytes := single_to_bytes4(value);
  writeln('{'+bytes4_string(little_endian_value_bytes)+'}'); // {$CD $CC $F6 $42} auf x86/Little Endian
  
  //so wuerde es (umgedreht) von einem Big Endian System kommen (z.B. die SPS oder ARM usw.)
  big_endian_value_bytes[0] := $42;
  big_endian_value_bytes[1] := $F6;
  big_endian_value_bytes[2] := $CC;
  big_endian_value_bytes[3] := $CD;
  writeln('{'+bytes4_string(big_endian_value_bytes)+'}'); // {$42 $F6 $CC $CD}
  little_endian_value_bytes := reverse_bytes4(big_endian_value_bytes); // aus Big wird Little Endian
  writeln('{'+bytes4_string(little_endian_value_bytes)+'}'); // {$CD $CC $F6 $42} Little Endian
  value := bytes4_to_single(little_endian_value_bytes);
  writeln(Format('%.4f',[value])); // 123.4000
end.

Uses sysutils;
type
  TBytes4 = array[0..3] of Byte;
  
function bytes4_string(value_bytes: TBytes4): string;
var
  i: integer;
  result: string;
begin
  result := '';
  for i := 0 to sizeof(value_bytes)-1 do 
  begin
    result += Format('$%.2x',[value_bytes[i]]);
    if(i < sizeof(value_bytes)-1) then
    begin
      result += ' ';
    end;
  end;
  bytes4_string := result;
end;
  
function single_to_bytes4(value: Single): TBytes4;
var
  value_bytes: TBytes4 absolute value;
begin
  single_to_bytes4 := value_bytes;
end;


function bytes4_to_single(value_bytes: TBytes4): Single;
var
  result: Single absolute value_bytes;
begin
  bytes4_to_single := result;
end;


function reverse_bytes4(value_bytes: TBytes4): TBytes4;
var
  i: integer;
  result: TBytes4;
begin
  for i := 0 to sizeof(value_bytes)-1 do 
  begin
    result[i] := value_bytes[sizeof(value_bytes)-1-i];
  end;
  reverse_bytes4 := result;
end;
  
var
  value: Single;
  little_endian_value_bytes: TBytes4;
  big_endian_value_bytes: TBytes4;
begin
  writeln('Bytes in Single umwandeln');
  little_endian_value_bytes[0] := $00;
  little_endian_value_bytes[1] := $00;
  little_endian_value_bytes[2] := $C8;
  little_endian_value_bytes[3] := $42;
  writeln('{'+bytes4_string(little_endian_value_bytes)+'}'); // {$00 $00 $C8 $42} auf x86/Little Endian
  value := bytes4_to_single(little_endian_value_bytes);
  writeln(Format('%.4f',[value])); // 100.0000
  
  writeln('Wert in 4 Bytes umwandeln');
  value := 100.0;
  writeln(Format('%.4f',[value])); // 100.0000
  little_endian_value_bytes := single_to_bytes4(value);
  writeln('{'+bytes4_string(little_endian_value_bytes)+'}'); // {$00 $00 $C8 $42} auf x86/Little Endian
end.