Welcome to our new forum
All users of the legacy CODESYS Forums, please create a new account at account.codesys.com. But make sure to use the same E-Mail address as in the old Forum. Then your posts will be matched. Close

Reading from serial communication

Engineering 🇬🇧
damian177
2021-12-22
2021-12-22

  • damian177 - 2021-12-22

    Hi,
    I try do communication on RS232. I do write Data but I have a problem with read Data. Someone can hel me with code to read data form RS232 ?

    In the following code:

    VAR
   rdData: ARRAY[0..41] OF BYTE;  //buf
END_VAR
IF hCom <> RTS_INVALID_HANDLE AND bReadCom THEN
    // Read data
    dwRead := SysComRead(hCom:= hCom, pbyBuffer:= ADR(rdData), ulSize:= SIZEOF(rdData), ulTimeout:= 100, pResult:= ADR(Result));
    IF dwRead > 0 THEN
        ///??
    END_IF
    bReadCom:=FALSE;

END_IF

    I would like save bytes to my bufor beggining <stx> byte (including) and ending on <ext> + last byte(wher Should be CRC sum). How do this ?</ext></stx>

     

  • damian177 - 2021-12-22

    I done something like this. It works. But probably it not an optimal solution:

    //timeout to receive  complete message
tonRcv(IN:= (iCountG>0) AND NOT tonRcv.Q, PT:=T#20S);

IF hCom <> RTS_INVALID_HANDLE AND bReadCom THEN
    // Complete the data
    numberOfbytes := SysComRead(hCom:= hCom, pbyBuffer:= ADR(temp_rdData), ulSize:= SIZEOF(temp_rdData), ulTimeout:= 100, pResult:= ADR(Result));
    IF numberOfbytes > 0 THEN
        FOR iCount :=0 TO numberOfbytes-1 DO
            rdData[iCountG]:=temp_rdData[iCount];
            iCountG:= iCountG +1;
        END_FOR
    END_IF
    //check if all data and  CRC sum OK 
        IF find_chars(ADR(rdData), UDINT_TO_BYTE(iCountG), ctrl.STX, ctrl.ETX) THEN 
            IF calc_CRC(ADR(rdData), UDINT_TO_BYTE(iCountG)-1) = rdData[iCountG-1] THEN
                iCountG:=0; 
                weHaveWholePackage:=TRUE; 
                bReadCom:=FALSE;    
            END_IF; 
        END_IF;

END_IF
     

Log in to post a comment.