Example: Memory ring FiFo (FB_MemRingBufferEx)

Here you can unpack the complete sources: MemRingBufferExExample.zip

A rising edge at bAdd causes new data elements (pubObj array) to be stored in the ring buffer. Via a rising edge at bGet the oldest data element can then be copied to the getObj variable.

Data elements that are not required are removed from the buffer via a rising edge at bRelease.

PROGRAM MAIN
VAR
    fbBuffer        : FB_MemRingBufferEx;
    buffer      : ARRAY[0..30] OF BYTE;
    bAdd, bGet, bRelease, bReset, bGetFree : BOOL;
    putObj      : ARRAY[0..3] OF BYTE := 16#00, 16#AA, 16#BB, 16#CC;
    getObj      : ARRAY[0..3] OF BYTE := 4(0);
    bOk         : BOOL;
    nCount      : UDINT;
    cbSize      : UDINT;
    cbFree      : UDINT;
END_VAR

IF bAdd THEN
    bAdd := FALSE;
    putObj[0] := putObj[0] + 1;(* modify data *)
    fbBuffer.A_AddTail(pBuffer := ADR( buffer ), cbBuffer := SIZEOF( buffer ),
            pWrite := ADR( putObj ), cbWrite := SIZEOF( putObj ),
            bOk=>bOk, nCount=>nCount, cbSize=>cbSize, cbFree=>cbFree );
    IF fbBuffer.bOk THEN
        ;(* Success *)
    ELSE
        ;(* Buffer overflow *)
    END_IF
END_IF

IF bGet THEN
    bGet := FALSE;
    fbBuffer.A_GetHead(pBuffer := ADR( buffer ), cbBuffer := SIZEOF( buffer ),
            bOk=>bOk, nCount=>nCount, cbSize=>cbSize, cbFree=>cbFree );
    IF fbBuffer.bOk THEN
        (* Success *)
        MEMCPY( ADR( getObj ), fbBuffer.pRead, MIN( SIZEOF( getObj ), fbBuffer.cbRead ) );
    ELSE
        ;(* Buffer empty *)
    END_IF
END_IF

IF bRelease THEN
    bRelease := FALSE;
    fbBuffer.A_FreeHead( pBuffer := ADR( buffer ), cbBuffer := SIZEOF( buffer ),
            bOk=>bOk, nCount=>nCount, cbSize=>cbSize, cbFree=>cbFree );
    IF fbBuffer.bOk THEN
        ;(* Success *)
    ELSE
        ;(* Buffer empty *)
    END_IF
END_IF

IF bGetFree THEN
    bGetFree := FALSE;
    fbBuffer.A_GetFreeSize(pBuffer := ADR( buffer ), cbBuffer := SIZEOF( buffer ),
            bOk=>bOk, nCount=>nCount, cbSize=>cbSize, cbFree=>cbFree );
END_IF

IF bReset THEN
    bReset := FALSE;
    fbBuffer.A_Reset(       pBuffer := ADR( buffer ), cbBuffer := SIZEOF( buffer ),
            bOk=>bOk,nCount=>nCount, cbSize=>cbSize, cbFree=>cbFree );
END_IF