I have some trouble using this function, it calculates the CRC of the transmitted message.
This is the original code:
if(ReceivedMessage[slot].Message[1] = $FD) and
(ReceivedMessage[ slot].MessageLength in [1..16]) and
(ReceivedMessage[slot].Message[counter] = $FF) then
begin
index := 2;
ReceivedMessage[slot].DataReady := TRUE;
for counter := 1 to ReceivedMessage[slot].MessageLength do
begin
Inc(index);
< br /> if ReceivedMessage[slot].Message[index] <$F8 then
ReceivedMessage[slot].Data[counter] := ReceivedMessage[slot].Message[index]
else
if ReceivedMessage[slot].Message[index] = $F8 then
begin
Inc(index);
ReceivedMessage[slot].Data[counter] := ReceivedMessage[slot ].Message[index] or $F0;
end
else
ReceivedMessage[slot].DataReady := FALSE; // Invalid data
end;
if ReceivedMessage[slot].DataReady = TRUE then
begin
Inc(index );
if ReceivedMessage[slot].Message[index] <$F8 then
ReceivedMessage[slot].CRC := ReceivedMessage[slot].Message[index] shl 8
else
if ReceivedMessage[slot].Message[index] = $F8 then
begin
Inc(index);
ReceivedMessage[slot].CRC := (ReceivedMessage[slot].Message[index] or $F0) shl 8;
end;
Inc(index);
if ReceivedMessage[slot]. Message[index] <$F8 then
ReceivedMessage[slot].CRC := ReceivedMessage[slot].CRC or ReceivedMessage[slot].Message[index]
else
if ReceivedMessage[slot] .Message[index] = $F8 then
begin
Inc(index);
ReceivedMessa ge[slot].CRC := ReceivedMessage[slot].CRC or ReceivedMessage[slot].Message[index] or $F0;
end;
This is my Java code:
if(array[1]==0xFD && (array[2]>0 && array[2]<17) && array[pos]==(byte)0xFF)< br /> {
index=2;
for(int counter=1;counter
index++;
if( array[index]<0xF8)
data[counter]=array[index];
else
if(array[index]==0xF8)
{
index++ ;
data[counter]=(byte)(array[index] | 0xF0);
}
else
return 0xFC;
}
index++;
short crc=0x0000;
if(array[index]<0xF8)
crc=(short) (array[index]<< 8);
else
if(array[index]==0xF8)
{
index++;
crc=(short)((array[index] | 0xF0 ) << 8);
}
index++;
if(array[index]<0xF8)
crc=(short) (crc | array[index]);
else
if(array[index]==0xF8)
{
index+ +;
crc=(short)(crc | array[index] | 0xF0);
}
msgcrc=new byte[] {(byte)(crc >> 8 & 0xff),(byte)(crc & 0xff));
My function returns the transmitted CRC code most of the time, but sometimes it fails and returns the last two bytes of the message. At the end of the message The 3 bytes are the CRC code (2 bytes) and the end of the message 0xff byte.
Does it help?
Thank you,
Pedro
Java bytes are signed. So:
byte test = (byte)255;
System.out.println(test);
will output: -1
and
byte test = (byte)255;
System.out. println(test == 255);
An error will be printed, but
byte test = (byte)255;
System.out. println((test & 255) == 255);
will do what I think you want to achieve (print as true in this case).
To get nothing Symbol (byte) value, please use (array [index]& 255).
You will have to use 0xff for masking everywhere, otherwise you will get a sign extended integer of byte value greater than 127 .
For comparison, you can also always perform conversion to bytes (e.g. if(test ==(byte)255)) but I think a single conversion should be adhered to, so I recommend masking with &0xff. < /p>
I am porting an old application written in Delphi to Java.
I have some trouble using this function, it calculates the CRC of the transmitted message .
This is the original code:
if(ReceivedMessage[slot].Message[1] = $FD) and
(ReceivedMessage[slot].MessageLength in [1..16]) and
(ReceivedMessage[slot].Message[counter] = $FF) then
begin
index := 2;< br /> ReceivedMessag e[slot].DataReady := TRUE;
for counter := 1 to ReceivedMessage[slot].MessageLength do
begin
Inc(index);
< br /> if ReceivedMessage[slot].Message[index] <$F8 then
ReceivedMessage[slot].Data[counter] := ReceivedMessage[slot].Message[index]
else
if ReceivedMessage[slot].Message[index] = $F8 then
begin
Inc(index);
ReceivedMessage[slot].Data[counter] := ReceivedMessage[slot ].Message[index] or $F0;
end
else
ReceivedMessage[slot].DataReady := FALSE; // Invalid data
end;
if ReceivedMessage[slot].DataReady = TRUE then
begin
Inc(index);
if ReceivedMessage[slot].Message[index] <$F8 then
ReceivedMessage[slot].CRC := ReceivedMessage[slot].Message[index] shl 8
else
if ReceivedMessage[slot].Message[index] = $F8 then
begin
Inc(index);
ReceivedMessage[slot].CRC := (ReceivedMessage[slot]. Message[index] or $F0) shl 8;
end;
Inc(index);
if ReceivedMessage[slot].Message[index] <$ F8 then
ReceivedMessage[slot].CRC := ReceivedMessage[slot].CRC or ReceivedMessage[slot].Message[index]
else
if ReceivedMessage[slot].Message[index] = $F8 then
begin
Inc(index);
ReceivedMessage[slot].CRC := ReceivedMessage[slot].CRC or ReceivedMessage[slot].Message[index] or $F0;
end;
This is my Java code:
if(array[1]==0xFD && (array[ 2]>0 && array[2]<17) && array[pos]==(byte)0xFF)
{
index=2;
for(int counter=1;counter< splMsg.nbytes+1;counter++)
{
index++;
if(array[index]<0xF8)
data[count er]=array[index];
else
if(array[index]==0xF8)
{
index++;
data[counter]=(byte) (array[index] | 0xF0);
}
else
return 0xFC;
}
index++;
short crc=0x0000;
if(array[index]<0xF8)
crc=(short) (array[index]<<8);
else
if (array[index]==0xF8)
{
index++;
crc=(short)((array[index] | 0xF0) << 8);
}
index++;
if(array[index]<0xF8)
crc=(short) (crc | array[index]);
else
if(array[index] ==0xF8)
{
index++;
crc=(short)(crc | array[index] | 0xF0);
}
msgcrc= new byte[] {(byte)(crc >> 8 & 0xff),(byte)(crc & 0xff)};
My function returns the transmitted CRC code most of the time, but sometimes it fails And return the last two bytes of the message. The last 3 bytes of the message are the CRC code (2 bytes) and the end of the message 0xff bytes.
Does it help?
Thank you,
Pedro
Remember:
Java bytes are signed .So:
byte test = (byte)255;
System.out.println(test);
will output: -1
and
byte test = (byte)255;
System.out.println(test == 255);
An error will be printed, but
byte test = (byte)255;
System.out.println((test & 255) == 255);
Will do what I think you want to achieve (print true in this case).
To get an unsigned (byte) value, use (array [ index]& 255).
You will have to use 0xff for masking everywhere, otherwise you will get sign extended integers with byte values greater than 127.
For comparison, you It is also possible to always perform conversion to bytes (e.g. if (test == (byte) 255)) but I think a single conversion should be adhered to, so I recommend masking with &0xff.
p>