Porting FreeRTOS+TCP to a Different Microcontroller

BaseType_t xNetworkInterfaceInitialise( void );
								

BaseType_t xNetworkInterfaceOutput( NetworkBufferDescriptor_t * const pxDescriptor,
                                    BaseType_t xReleaseAfterSend );
								

void vNetworkInterfaceAllocateRAMToBuffers(
       NetworkBufferDescriptor_t xDescriptors[ ipconfigNUM_NETWORK_BUFFERS ] );
								

/* First statically allocate the buffers, ensuring an additional ipBUFFER_PADDING
bytes are allocated to each buffer.  This example makes no effort to align
the start of the buffers, but most hardware will have an alignment requirement.
If an alignment is required then the size of each buffer must be adjusted to
ensure it also ends on an alignment boundary.  Below shows an example assuming
the buffers must also end on an 8-byte boundary. */
#define BUFFER_SIZE ( ipTOTAL_ETHERNET_FRAME_SIZE + ipBUFFER_PADDING )
#define BUFFER_SIZE_ROUNDED_UP ( ( BUFFER_SIZE + 7 ) & ~0x07UL )
static uint8_t ucBuffers[ ipconfigNUM_NETWORK_BUFFERS ][ BUFFER_SIZE_ROUNDED_UP ];

/* Next provide the vNetworkInterfaceAllocateRAMToBuffers() function, which
simply fills in the pucEthernetBuffer member of each descriptor. */
void vNetworkInterfaceAllocateRAMToBuffers(
    NetworkBufferDescriptor_t pxNetworkBuffers[ ipconfigNUM_NETWORK_BUFFERS ] )
{
BaseType_t x;

    for( x = 0; x < ipconfigNUM_NETWORK_BUFFERS; x++ )
    {
        /* pucEthernetBuffer is set to point ipBUFFER_PADDING bytes in from the
        beginning of the allocated buffer. */
        pxNetworkBuffers[ x ].pucEthernetBuffer = &( ucBuffers[ x ][ ipBUFFER_PADDING ] );

        /* The following line is also required, but will not be required in
        future versions. */
        *( ( uint32_t * ) &ucBuffers[ x ][ 0 ] ) = ( uint32_t ) &( pxNetworkBuffers[ x ] );
    }
}
								

typedef struct IP_TASK_COMMANDS
{
    /* Specifies the type of event being sent to the RTOS task and must be set to
    eNetworkRxEvent to signify a receive event. */
    eIPEvent_t eEventType;

    /* Points to additional data about the event.  In this case set pvData to the
    the address of the network buffer descriptor. */
    void *pvData;
} IPStackEvent_t;
								

/* The timeout is specified in RTOS ticks.  Returns pdTRUE if the message was
sent successfully, otherwise return pdFALSE. */
BaseType_t xSendEventStructToIPTask( const IPStackEvent_t *pxEvent, TickType_t xTimeout )
								

BaseType_t xNetworkInterfaceInitialise( void )
{
BaseType_t xReturn;

    /*
     * Perform the hardware specific network initialisation here.  Typically
     * that will involve using the Ethernet driver library to initialise the
     * Ethernet (or other network) hardware, initialise DMA descriptors, and
     * perform a PHY auto-negotiation to obtain a network link.
     *
     * This example assumes InitialiseNetwork() is an Ethernet peripheral driver
     * library function that returns 0 if the initialisation fails.
     */
    if( InitialiseNetwork() == 0 )
    {
        xReturn = pdFAIL;
    }
    else
    {
        xReturn = pdPASS;
    }

    return xReturn;
}
								

BaseType_t xNetworkInterfaceOutput( NetworkBufferDescriptor_t * const pxDescriptor,
                                    BaseType_t xReleaseAfterSend )
{
    /* Simple network interfaces (as opposed to more efficient zero copy network
    interfaces) just use Ethernet peripheral driver library functions to copy
    data from the FreeRTOS+TCP buffer into the peripheral driver's own buffer.
    This example assumes SendData() is a peripheral driver library function that
    takes a pointer to the start of the data to be sent and the length of the
    data to be sent as two separate parameters.  The start of the data is located
    by pxDescriptor->pucEthernetBuffer.  The length of the data is located
    by pxDescriptor->xDataLength. */
    SendData( pxDescriptor->pucBuffer, pxDescriptor->xDataLength );

    /* Call the standard trace macro to log the send event. */
    iptraceNETWORK_INTERFACE_TRANSMIT();

    if( xReleaseAfterSend != pdFALSE )
    {
        /* It is assumed SendData() copies the data out of the FreeRTOS+TCP Ethernet
        buffer.  The Ethernet buffer is therefore no longer needed, and must be
        freed for re-use. */
        vReleaseNetworkBufferAndDescriptor( pxDescriptor );
    }

    return pdTRUE;
}
								

/* The deferred interrupt handler is a standard RTOS task.  FreeRTOS's centralised
deferred interrupt handling capabilities can also be used. */
static void prvEMACDeferredInterruptHandlerTask( void *pvParameters )
{
NetworkBufferDescriptor_t *pxBufferDescriptor;
size_t xBytesReceived;
/* Used to indicate that xSendEventStructToIPTask() is being called because
of an Ethernet receive event. */
IPStackEvent_t xRxEvent;

    for( ;; )
    {
        /* Wait for the Ethernet MAC interrupt to indicate that another packet
        has been received.  The task notification is used in a similar way to a
        counting semaphore to count Rx events, but is a lot more efficient than
        a semaphore. */
        ulTaskNotifyTake( pdFALSE, portMAX_DELAY );

        /* See how much data was received.  Here it is assumed ReceiveSize() is
        a peripheral driver function that returns the number of bytes in the
        received Ethernet frame. */
        xBytesReceived = ReceiveSize();

        if( xBytesReceived > 0 )
        {
            /* Allocate a network buffer descriptor that points to a buffer
            large enough to hold the received frame.  As this is the simple
            rather than efficient example the received data will just be copied
            into this buffer. */
            pxBufferDescriptor = pxGetNetworkBufferWithDescriptor( xBytesReceived, 0 );

            if( pxBufferDescriptor != NULL )
            {
                /* pxBufferDescriptor->pucEthernetBuffer now points to an Ethernet
                buffer large enough to hold the received data.  Copy the
                received data into pcNetworkBuffer->pucEthernetBuffer.  Here it
                is assumed ReceiveData() is a peripheral driver function that
                copies the received data into a buffer passed in as the function's
                parameter.  Remember! While is is a simple robust technique -
                it is not efficient.  An example that uses a zero copy technique
                is provided further down this page. */
                ReceiveData( pxBufferDescriptor->pucEthernetBuffer );
                pxBufferDescriptor->xDataLength = xBytesReceived;

                /* See if the data contained in the received Ethernet frame needs
                to be processed.  NOTE! It is preferable to do this in
                the interrupt service routine itself, which would remove the need
                to unblock this task for packets that don't need processing. */
                if( eConsiderFrameForProcessing( pxBufferDescriptor->pucEthernetBuffer )
                                                                      == eProcessBuffer )
                {
                    /* The event about to be sent to the TCP/IP is an Rx event. */
                    xRxEvent.eEventType = eNetworkRxEvent;

                    /* pvData is used to point to the network buffer descriptor that
                    now references the received data. */
                    xRxEvent.pvData = ( void * ) pxBufferDescriptor;

                    /* Send the data to the TCP/IP stack. */
                    if( xSendEventStructToIPTask( &xRxEvent, 0 ) == pdFALSE )
                    {
                        /* The buffer could not be sent to the IP task so the buffer
                        must be released. */
                        vReleaseNetworkBufferAndDescriptor( pxBufferDescriptor );

                        /* Make a call to the standard trace macro to log the
                        occurrence. */
                        iptraceETHERNET_RX_EVENT_LOST();
                    }
                    else
                    {
                        /* The message was successfully sent to the TCP/IP stack.
                        Call the standard trace macro to log the occurrence. */
                        iptraceNETWORK_INTERFACE_RECEIVE();
                    }
                }
                else
                {
                    /* The Ethernet frame can be dropped, but the Ethernet buffer
                    must be released. */
                    vReleaseNetworkBufferAndDescriptor( pxBufferDescriptor );
                }
            }
            else
            {
                /* The event was lost because a network buffer was not available.
                Call the standard trace macro to log the occurrence. */
                iptraceETHERNET_RX_EVENT_LOST();
            }
        }
    }
}
								

BaseType_t xNetworkInterfaceOutput( NetworkBufferDescriptor_t * const pxDescriptor,
                                    BaseType_t xReleaseAfterSend )
{
DMADescriptor_t *pxDMATxDescriptor;

    /* This example assumes GetNextTxDescriptor() is an Ethernet MAC driver library
    function that returns a pointer to a DMA descriptor of type DMADescriptor_t. */
    pxDMATxDescriptor = GetNextTxDescriptor();

    /* Further, this example assumes the DMADescriptor_t type has a member
    called pucEthernetBuffer that points to the buffer the DMA will transmit, and
    a member called xDataLength that holds the length of the data the DMA will
    transmit.  If BufferAllocation_2.c is being used then the DMA descriptor may
    still be pointing to the buffer it last transmitted.  If this is the case
    then the old buffer must be released (returned to the TCP/IP stack) before
    descriptor is updated to point to the new data waiting to be transmitted. */
    if( pxDMATxDescriptor->pucEthernetBuffer != NULL )
    {
        /* Note this is releasing just an Ethernet buffer, not a network buffer
        descriptor as the descriptor has already been released. */
        vReleaseNetworkBuffer( pxDMATxDescriptor->pucEthernetBuffer );
    }

    /* Configure the DMA descriptor to send the data referenced by the network buffer
    descriptor.  This example assumes SendData() is an Ethernet peripheral driver
    function. */
    pxDMATxDescriptor->pucEthernetBuffer = pxDescriptor->pucEthernetBuffer;
    pxDMATxDescriptor->xDataLength = pxDescriptor->xDataLength;
    SendData( pxDMATxDescriptor );

    /* Call the standard trace macro to log the send event. */
    iptraceNETWORK_INTERFACE_TRANSMIT();

    /* The network buffer descriptor must now be returned to the TCP/IP stack, but
    the Ethernet buffer referenced by the network buffer descriptor is still in
    use by the DMA.  Remove the reference to the Ethernet buffer from the network
    buffer descriptor so releasing the network buffer descriptor does not result
    in the Ethernet buffer also being released.  xReleaseAfterSend() should never
    equal pdFALSE when  ipconfigZERO_COPY_TX_DRIVER is set to 1 (as it should be
    if data is transmitted using a zero copy driver.*/
    if( xReleaseAfterSend != pdFALSE )
    {
        pxDescriptor->pucEthernetBuffer = NULL;
        vReleaseNetworkBufferAndDescriptor( pxDescriptor );
    }

    return pdTRUE;
}
								

/* The deferred interrupt handler is a standard RTOS task.  FreeRTOS's centralised
deferred interrupt handling capabilities can also be used - however for additional
speed use BufferAllocation_1.c to perform the entire operation in the interrupt
handler. */
static void prvEMACDeferredInterruptHandlerTask( void *pvParameters )
{
NetworkBufferDescriptor_t *pxDescriptor;
size_t xBytesReceived;
DMADescriptor_t *pxDMARxDescriptor;
uint8_t *pucTemp;
/* Used to indicate that xSendEventStructToIPTask() is being called because
of an Ethernet receive event. */
IPStackEvent_t xRxEvent;

  for( ;; )
  {
    /* Wait for the Ethernet MAC interrupt to indicate that another packet
    has been received.  The task notification is used in a similar way to a
    counting semaphore to count Rx events, but is a lot more efficient than
    a semaphore. */
    ulTaskNotifyTake( pdFALSE, portMAX_DELAY );

    /* This example assumes GetNextRxDescriptor() is an Ethernet MAC driver
    library function that returns a pointer to the DMA descriptor (of type
    DMADescriptor_t again) that references the Ethernet buffer containing the
    received data. */
    pxDMARxDescriptor = GetNextRxDescriptor();

    /* Allocate a new network buffer descriptor that references an Ethernet
    frame large enough to hold the maximum network packet size (as defined
    in the FreeRTOSIPConfig.h header file). */
    pxDescriptor = pxGetNetworkBufferWithDescriptor( ipTOTAL_ETHERNET_FRAME_SIZE, 0 );

    /* Copy the pointer to the newly allocated Ethernet frame to a temporary
    variable. */
    pucTemp = pxDescriptor->pucEthernetBuffer;

    /* This example assumes that the DMADescriptor_t type has a member
    called pucEthernetBuffer that points to the Ethernet buffer containing
    the received data, and a member called xDataLength that holds the length
    of the received data.  Update the newly allocated network buffer descriptor
    to point to the Ethernet buffer that contains the received data. */
    pxDescriptor->pucEthernetBuffer = pxDMARxDescriptor->pucEthernetBuffer;
    pxDescriptor->xDataLength = pxDMARxDescriptor->xDataLength;

    /* Update the Ethernet Rx DMA descriptor to point to the newly allocated
    Ethernet buffer. */
    pxDMARxDescriptor->puxEthernetBuffer = pucTemp;

    /* A pointer to the descriptor is stored at the front of the buffer, so
    swap these too. */
    *( ( NetworkBufferDescriptor_t ** )
       ( pxDescriptor->pucEthernetBuffer - ipBUFFER_PADDING ) ) = pxDescriptor;

    *( ( NetworkBufferDescriptor_t ** )
       ( pxDMARxDescriptor->pucEthernetBuffer - ipBUFFER_PADDING ) ) = pxDMARxDescriptor;

    /*
     * The network buffer descriptor now points to the Ethernet buffer that
     * contains the received data, and the Ethernet DMA descriptor now points
     * to a newly allocated (and empty) Ethernet buffer ready to receive more
     * data.  No data was copied.  Only pointers to data were swapped.
     *
     * THE REST OF THE RECEIVE HANDLER FUNCTION FOLLOWS THE EXAMPLE PROVIDED
     * FOR THE SIMPLE ETHERNET INTERFACE IMPLEMENTATION, whereby the network
     * buffer descriptor is sent to the TCP/IP on the network event queue.
     */



    /* See if the data contained in the received Ethernet frame needs
    to be processed.  NOTE! It might be possible to do this in
    the interrupt service routine itself, which would remove the need
    to unblock this task for packets that don't need processing. */
    if( eConsiderFrameForProcessing( pxDescriptor->pucEthernetBuffer )
                                == eProcessBuffer )
    {
      /* The event about to be sent to the TCP/IP is an Rx event. */
      xRxEvent.eEventType = eNetworkRxEvent;

      /* pvData is used to point to the network buffer descriptor that
      references the received data. */
      xRxEvent.pvData = ( void * ) pxDescriptor;

      /* Send the data to the TCP/IP stack. */
      if( xSendEventStructToIPTask( &xRxEvent, 0 ) == pdFALSE )
      {
        /* The buffer could not be sent to the IP task so the buffer
        must be released. */
        vReleaseNetworkBufferAndDescriptor( pxDescriptor );

        /* Make a call to the standard trace macro to log the
        occurrence. */
        iptraceETHERNET_RX_EVENT_LOST();
      }
      else
      {
        /* The message was successfully sent to the TCP/IP stack.
        Call the standard trace macro to log the occurrence. */
        iptraceNETWORK_INTERFACE_RECEIVE();
      }
    }
    else
    {
      /* The Ethernet frame can be dropped, but the Ethernet buffer
      must be released. */
      vReleaseNetworkBufferAndDescriptor( pxDescriptor );
    }
  }
}