Re: [fpc-pascal] Calculating CRC16?
On Tue, 25 Oct 2022 08:30:19 +0200, Bo Berglund via fpc-pascal
wrote:
>I am working on a handler for IoT data from an electricity meter which
>communicates via TTL serial at 115200 baud. It only sends data in packets of
>less than 1 kbytes every 5-10 seconds.
>
>In order to validate the data I need to check the CRC16 checksum at the end and
>here is where I don't find a good way to do it...
>The application will run on Linux so I checked for operating support but found
>only sksum, which apparently does not do CRC16.
>
>Is there some package or code available somewhere which can calculate the CRC16
>value over a byte array of some 1000 bytes?
>
>In a description of the protocol after showing the data structure it adds this:
>
>crc16 = libscrc.ibm(example_data).to_bytes(2, 'big').hex() >> '7945'
>
>Googling libscrc brings me to Python code on GitHub, which I am not really able
>to use, never programmed Python...
>https://github.com/hex-in/libscrc
>
>Anyone able to help with FPC implementation?
I have found a c++ function that purportedly does CRC16:
unsigned int CRC16(unsigned int crc, unsigned char *buf, int len)
{
for (int pos = 0; pos < len; pos++)
{
crc ^= (unsigned int)buf[pos];// * XOR byte into least sig.
byte of
crc
// * Loop over each bit
for (int i = 8; i != 0; i--)
{
// * If the LSB is set
if ((crc & 0x0001) != 0)
{
// * Shift right and XOR 0xA001
crc >>= 1;
crc ^= 0xA001;
}
// * Else LSB is not set
else
// * Just shift right
crc >>= 1;
}
}
return crc;
}
Can someone please decode this into pascal?
--
Bo Berglund
Developer in Sweden
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Re: [fpc-pascal] Calculating CRC16?
On Tue, 25 Oct 2022 08:30:19 +0200 Bo Berglund via fpc-pascal wrote: > Is there some package or code available somewhere which can calculate the > CRC16 > value over a byte array of some 1000 bytes? http://www.retroarchive.org/swag/CRC/index.html -- Simplex sigillum veri ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Calculating CRC16?
Hi, On 2022-10-25 09:30, Bo Berglund via fpc-pascal wrote: < snip > Anyone able to help with FPC implementation? Take a look here, https://forum.lazarus.freepascal.org/index.php?topic=54791.0 regards, -- Dimitrios Chr. Ioannidis ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Calculating CRC16?
I couldn't verify the code but it should be relatively close to your c++ example. Not sure of the width of int type, I supposed it's 16 bits wide: function CRC16( crc: Word; buf: PByte; len: Word; Poly:Word=$A001): Word; var pos: Word; i: Word; begin for pos:= 0 to len-1 do begin crc:= crc xor Word(buf[pos]); // * XOR byte into least sig. byte of crc // * Loop over each bit for i:= 8 downto 1 do begin // * If the LSB is set if ((crc and $0001) <> 0) then begin // * Shift right and XOR 0xA001 crc:= crc shr 1; crc:= crc xor Poly; end // * Else LSB is not set else // * Just shift right crc:= crc shr 1; end; end; Result:= crc; end; var S: String; begin Readln( S); WriteLn( IntToHex( CRC16( 0, PByte(@S[1]), Length(S), $8005), 4)); end. ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Calculating CRC16?
Il 25/10/22 09:58, Marco Borsari via fpc-pascal ha scritto: On Tue, 25 Oct 2022 08:30:19 +0200 Bo Berglund via fpc-pascal wrote: Is there some package or code available somewhere which can calculate the CRC16 value over a byte array of some 1000 bytes? http://www.retroarchive.org/swag/CRC/index.html Maybe you'll find this implementation more efficient: https://gist.github.com/prof7bit/7fc558626f94bd8a81b7 Giuliano -- Do not do to others as you would have them do to you.They might have different tastes. ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Calculating CRC16?
To array of bytes, check this: https://github.com/fluisgirardi/pascalscada_v0/blob/master/src/scada/crc16utils.pas There are two routines: one to calculate, another to check if crc16 matches. Em ter., 25 de out. de 2022 às 08:13, Giuliano Colla via fpc-pascal < fpc-pascal@lists.freepascal.org> escreveu: > Il 25/10/22 09:58, Marco Borsari via fpc-pascal ha scritto: > > On Tue, 25 Oct 2022 08:30:19 +0200 > > Bo Berglund via fpc-pascal wrote: > > > >> Is there some package or code available somewhere which can calculate > the CRC16 > >> value over a byte array of some 1000 bytes? > > http://www.retroarchive.org/swag/CRC/index.html > > > Maybe you'll find this implementation more efficient: > > https://gist.github.com/prof7bit/7fc558626f94bd8a81b7 > > Giuliano > > -- > Do not do to others as you would have them do to you.They might have > different tastes. > > ___ > fpc-pascal maillist - fpc-pascal@lists.freepascal.org > https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal > -- The best regards, Fabio Luis Girardi PascalSCADA Project http://sourceforge.net/projects/pascalscada http://www.pascalscada.com ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
