CRC_CHECK and CRC_GEN

2020-02-27T19:34:26.929000Z

oscat304.lib all help about CRC functions in English

CRC_CHECK

FUNCTION CRC_CHECK : BOOL
VAR_INPUT
   pt : POINTER TO ARRAY[0..32000] OF BYTE;
   size : UINT;
END_VAR
VAR_INPUT CONSTANT
   Polynom_L : DWORD;
   Polynom_32 : BOOL;
END_VAR
VAR
END_VAR
(*
version 1.1   16. mar. 2008
programmer    hugo
tested by      tobias
CRC_CHECK checks a block of data for a crc checksum and returns true is the checksum is 0 and therfore a error free data transmission.
the CRC Polynom is specified with the config variable Polynom_L which holds the lowest 32 bits of the polynom and Polynom_33 which holds bit 33 of the Polynom.
A Polynom x4 + X + 1 is represented by 10011.
The input data is an array of byte of any size, the function is called by CRC_CHECK(ADR(array),SIZEOF(array)).
*)

CRC_GEN

FUNCTION CRC_GEN : DWORD
VAR_INPUT
   pt : POINTER TO ARRAY[0..32000] OF BYTE;
   size : UINT;
END_VAR
VAR_INPUT CONSTANT
   Polynom_L : DWORD;
   Polynom_32 : BOOL;
   init: DWORD;
   XOR_out : DWORD;
   rev_in : BOOL;
   rev_out : BOOL;
END_VAR
VAR
   polynom : DWORD;
   p_length : INT;
   BS : BYTE;
   data : DWORD;
   count : BYTE;
   temp : BOOL;
   step: INT;
   s4: INT;
END_VAR
(*
version 1.4   16. mar. 2008
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 Polynom_L which holds the lowest 32 bits of the polynom and Polynom_33 which holds bit 33 of the Polynom.
A Polynom x4 + X + 1 is represented by 10011.
The input data is an array of byte of any size, the function is called by CRC_GEN(ADR(array),SIZEOF(array)).
*)

CRC_CHECK and CRC_GEN

2020-02-27T19:34:25.598000Z

Thanks for the reply Avgur.

But my problem is that i don't know how to use the CRC_CHECK and CRC_GEN functions from the oscat304.lib

What i need is a guide on how to use the two functions.

My code so far is below.

PROGRAM COMM2

VAR

COMM2: SERIAL_INTERFACE;

M_RECVSTR: BOOL;

pReceiveStr:POINTER TO ARRAY[0..255] OF BYTE;

I:INT;

CRC: BOOL;

Polynom_32: BOOL;

END_VAR

COMM2( bCOM_PORT_NR := 2,

        utRECEIVE_BUFFER := RECEIVE_BUFFER,

        iBYTES_TO_SEND  := LEN(SEND_STRING),

        ptSEND_BUFFER       := ADR(SEND_STRING),

        xINIT                   := INIT,

            xOPEN_COM_PORT  := TRUE,

        xSTART_SEND     := SEND );

IF pReceiveStr = 0 THEN ( receive buffer with address of receivers initialize string )

  pReceiveStr := ADR( ReceiveString );

END_IF;

IF Receive_Buffer.Index>0 THEN ( new data is received )

     FOR i:=0 TO 255 DO

        pReceiveStr^[i]:=16#00; (* receive buffer delete *)

     END_FOR;

     FOR i:=0 TO Receive_Buffer.Index-1 DO

        pReceiveStr^[i] :=  Receive_Buffer.Data[ i ]; (* ring buffer data in receive buffer to copy *)

     END_FOR;

     M_RECVSTR:=TRUE;

END_IF;

IF CLEAR_BUFFER THEN ( new request will be sent )

FOR i:= 0 TO 255 DO

    Receive_Buffer.Data[i] := 0; (* receive buffer delete *)

END_FOR

Receive_Buffer.Index := 0; ( receive buffer delete )

END_IF

CRC:= CRC_CHECK(pRECEIVESTR, I, 469, Polynom_32);

Any help would be appreciated.

Dave

CRC_CHECK and CRC_GEN

2020-02-27T19:34:22.093000Z

Try to google "A painless guide to CRC error detection algorithms"

Good luck!

CRC_CHECK and CRC_GEN

2020-02-27T19:34:20.849000Z

Can anyone help me with CRC_CHECK and CRC_GEN libraries from oscat304.lib.

My project is using a Wago 750-650 RS232 card to communicate with a laptop. The customer has asked me to use crc and i found the oscat library after some seaching. My problem is, i don't know how to use them. All the information i can find is in German. Can anyone provide me with an example codesys project or provide a step by step guide to implement CRC.

Thank You

Dave

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