CRC8 with XOR in Hex, Hex input

Engineering 🇬🇧
Vijolica555
2019-03-13
2019-03-22

  • Vijolica555 - 2019-03-13

    Hello,

    I need to verify Telegram which i need to send through TCPIP. I need to calculate Checksum with XOR. The length is 1 Byte. My input is hex string and i need output also as Hex string.
    Does anybody know how to do it? I tried to write smt but unsuccessfully.
    I am checking chekcum at https://www.scadacore.com/tools/program ... alculator/ and first output is smt i need.

    i tried to help myself with https://forum-de.codesys.com/viewtopic.php?t=456#p1679:
    Here is ok 16bit and WORD so i need to change that bu i dont understand statement inside of IF condition.

    FOR n := 1 TO 8 DO
  IF (wCRC16.0 = TRUE) THEN
    wCRC16 := SHR(wCRC16,1);
    wCRC16 := wCRC16 XOR c_wGenerator;
  ELSE
    wCRC16 := SHR(wCRC16,1);
  END_IF  
END_FOR

    So if anybody knows how to calculate CRC8 with Hex string input would really appreciate for help.

    IMG: Capture.PNG

     

  • dFx

    dFx - 2019-03-13

    Just in case you missed it, TCP/IP already have built in CRC check, so your received data can't be corrupted (if so, the network card will itself ask for the packet again, and will not provide you data).

    Edit : Also CRC8 and CRC16 are different.
    You could use oscat basic library for computing/checking CRC8

     

  • Vijolica555 - 2019-03-14

    Hello,

    Hmm actually i need to calculate checksum to send it at the end of telegram to get the response. So my Telegram is assembled from: header, data length, data and checksum of data. data is representing command. I have two possibilities: to send ASCII telegram where i can write in ASCII or hex or i send binary telegram in hexadecimal code. received answer is in hexadecimal code so i thought ok lets have all in hex. i use twincat and have beckhoffs PLC and The checksum of the TCIP telegram is not transferred into TwinCAT. Because of this also Oscar lib doesn't help me. Or is there possibility to open it in TwinCAT?

     

  • dFx

    dFx - 2019-03-14

    oscat CRC_GEN code:

    FUNCTION CRC_GEN : DWORD
VAR_INPUT
   PT : POINTER TO ARRAY[0..32000] OF BYTE;
   SIZE : INT;
   PL : INT;
   PN : DWORD;
   INIT : DWORD;
   REV_IN : BOOL;
   REV_OUT : BOOL;
   XOR_OUT : DWORD;
END_VAR
VAR
   pos : INT;
   shift : INT;
   dx: BYTE;
   bits: INT;
END_VAR
(*
version 2.0   16.Jan. 2011
programmer    hugo
tested by      tobias
CRC_GEN generates a CRC checksum from a block of data and returns  the checksum in a DWORD to be connected to the data for transmission.
the CRC Polynom is specified with the config variable PN and the length of the Polynom is specified by PL
A Polynom x4 + X + 1 is represented by 0011 with length 4, the highest order bit is not specified at all..
The input data is an array of byte of any size, the function is called by CRC_GEN(ADR(array),SIZEOF(array), ....).
*)
(* align polygon *)
shift := 32 - PL;
PN := SHL(PN, shift);
(* load first 4 bytes into register minimum message size is 4 bytes
   for smaller messages fill with 0#s at the beginning*)
FOR pos := 0 TO 3 DO
   IF REV_IN THEN CRC_GEN := SHL(CRC_GEN, 8) OR REVERSE(PT^[pos]); ELSE CRC_GEN := SHL(CRC_GEN, 8) OR PT^[pos]; END_IF;
END_FOR;
pos := 4;
(* xor with init value *)
CRC_GEN := CRC_GEN XOR SHL(init, shift);
(* calculate CRC for each byte *)
WHILE pos < size DO
   IF REV_IN THEN DX := REVERSE(PT^[pos]); ELSE DX := PT^[pos]; END_IF;
   pos := pos + 1;
   (* crc calculation for one byte *)
   FOR bits := 0 TO 7 DO
      IF CRC_GEN.31 THEN
         CRC_GEN := (SHL(CRC_GEN, 1) OR BOOL_TO_DWORD(DX.7)) XOR PN;
      ELSE
         CRC_GEN := SHL(CRC_GEN, 1) OR BOOL_TO_DWORD(DX.7);
      END_IF;
      dx := SHL(dx, 1);
   END_FOR;
END_WHILE;
(* all bytes are processed, need to finish the registers 32 bits *)
FOR bits := 0 TO 31 DO
   IF CRC_GEN.31 THEN
      CRC_GEN := (SHL(CRC_GEN, 1) OR BOOL_TO_DWORD(DX.7)) XOR PN;
   ELSE
      CRC_GEN := SHL(CRC_GEN, 1) OR BOOL_TO_DWORD(DX.7);
   END_IF;
END_FOR;
(* final XOR *)
CRC_GEN := SHR(CRC_GEN, shift) XOR XOR_OUT;
(* reverse the crc_out put if necessary *)
IF REV_OUT THEN CRC_GEN := REFLECT(CRC_GEN, PL); END_IF;
(* typical crc polynoms
CRC-4-ITU          x4 + x + 1                (ITU G.704, p. 12)    0x3 or 0xC (0x9)
CRC-5-ITU          x5 + x4 + x2 + 1          (ITU G.704, p. 9)    0x15 or 0x15 (0x0B) Bluetooth
CRC-5-USB          x5 + x2 + 1             (use: USB token packets)    0x05 or 0x14 (0x9)
CRC-6-ITU          x6 + x + 1                (ITU G.704, p. 3)    0x03 or 0x30 (0x21)
CRC-7             x7 + x3 + 1             (use: telecom systems, MMC)    0x09 or 0x48 (0x11)
CRC-8-ATM          x8 + x2 + x + 1             (use: ATM HEC)    0x07 or 0xE0 (0xC1)
CRC-8-CCITT       x8 + x7 + x3 + x2 + 1       (use: 1-Wire bus)    0x8D or 0xB1 (0x63)
CRC-8-Dallas/Maxim    x8 + x5 + x4 + 1          (use: 1-Wire bus)    0x31 or 0x8C (0x19)
CRC-8             x8 + x7 + x6 + x4 + x2 + 1    0xD5 or 0xAB (0x57)
CRC-8-SAE J1850    x8 + x4 + x3 + x2 + 1       0x1D or 0xB8
CRC-10             x10 + x9 + x5 + x4 + x + 1    0x233 or 0x331 (0x263)
CRC-12             x12 + x11 + x3 + x2 + x + 1 (use: telecom systems)    0x80F or 0xF01 (0xE03)
CRC-15-CAN          x15 + x14 + x10 + x8 + x7 + x4 + x3 + 1    0x4599 or 0x4CD1 (0x19A3)
CRC-16-Fletcher    Not a CRC; see Fletcher's checksum    Used in Adler-32 A & B CRCs
CRC-16-CCITT    x16 + x12 + x5 + 1 (XMODEM,X.25, V.41, Bluetooth, PPP, IrDA; known as "CRC-CCITT")    0x1021 or 0x8408 (0x0811)
CRC-16-IBM    x16 + x15 + x2 + 1 (USB, many others; also known as "CRC-16")    0x8005 or 0xA001 (0x4003)
CRC-24-Radix-64    x24 + x23 + x18 + x17 + x14 + x11 + x10 + x7 + x6 + x5 + x4 + x3 + x + 1    0x864CFB or 0xDF3261 (0xBE64C3)
CRC-32-Adler    Not a CRC; see Adler-32    See Adler-32
CRC-32-MPEG2    x32 + x26 + x23 + x22 + x16 + x12 + x11 + x10 + x8 + x7 + x5 + x4 + x2 + x + 1    0x04C11DB7 or 0xEDB88320 (0xDB710641) Also used in IEEE 802.3
CRC-32-IEEE 802.3    x32 + x26 + x23 + x22 + x16 + x12 + x11 + x10 + x8 + x7 + x5 + x4 + x2 + x + 1 (V.42)    0x04C11DB7 or 0xEDB88320 (0xDB710641)
CRC-32C (Castagnoli)    x32 + x28 + x27 + x26 + x25 + x23 + x22 + x20 + x19 + x18 + x14 + x13 + x11 + x10 + x9 + x8 + x6 + 1    0x1EDC6F41 or 0x82F63B78 (0x05EC76F1)
CRC-64-ISO    x64 + x4 + x3 + x + 1 (use: ISO 3309)    0x000000000000001B or 0xD800000000000000 (0xB000000000000001)
CRC-64-ECMA-182    x64 + x62 + x57 + x55 + x54 + x53 + x52 + x47 + x46 + x45 + x40 + x39 + x38 + x37 + x35 + x33 + x32 + x31 + x29 + x27 + x24 + x23 + x22 + x21 + x19 + x17 + x13 + x12 + x10 + x9 + x7 + x4 + x + 1
(as described in ECMA-182 p.63)    0x42F0E1EBA9EA3693 or 0xC96C5795D7870F42 (0x92D8AF2BAF0E1E85)
*)
(* revision history
hm   9.6.2007      rev 1.0      
   original version 
hm   11.9.2007      rev 1.1
   deleted unused variable i
hm   9. oct 2007    rev 1.2
   added init code for crc and xor_out
   added refelct in and reflect_out (rev_in und Rev_out)
hm   2. jan 2008   rev 1.3
   small changes for performance improvements
hm   16. mar. 2008   rev 1.4
   changed type of input size to uint
hm   10. mar. 2009   rev 1.5
   removed nested comments
hm   16. jan. 2011   rev 2.0
   new version
*)
     

  • Vijolica555 - 2019-03-22

    Thank you!

     

Log in to post a comment.