中断驱动字符队列传输模式

[FreeRTOS-Plus-IO 传输模式]

/* FreeRTOS-Plus-IO includes. */

#include "FreeRTOS_IO.h"



void vAFunction( void )

{

/* The Peripheral_Descriptor_t type is the FreeRTOS-Plus-IO equivalent of a descriptor. */

Peripheral_Descriptor_t xOpenedPort;

BaseType_t xReturned;

const uint32_t ulMaxBlock100ms = ( 100UL / portTICK_PERIOD_MS );



    /* Open the SPI port identified in the board support package as using the

    path string "/SPI2/".  The second parameter is not currently used and can

    be set to anything, although, for future compatibility, it is recommended 

    that it is set to NULL. */

    xOpenedPort = FreeRTOS_open( "/SPI2/", NULL );



    if( xOpenedPort != NULL )

    {

        /***************** Configure the port *********************************/

    

        /* xOpenedPort now contains a valid descriptor that can be used with

        other FreeRTOS-Plus-IO API functions.  

        

        Peripherals default to using Polled mode for both reads and  writes.

        Change from the default to use interrupt driven character queues for both

        reading and writing.  The third FreeRTOS_ioctl() parameter sets the

        queue length.   In this example, the length is set to 20 in both cases.

        A successful FreeRTOS_ioctl() call will return pdPASS, for simplicity,

        this example does not show the return value being checked. */

        FreeRTOS_ioctl( xOpenedPort, ioctlUSE_CHARACTER_QUEUE_RX, ( void * ) 20 );

        FreeRTOS_ioctl( xOpenedPort, ioctlUSE_CHARACTER_QUEUE_TX, ( void * ) 20 );

                

        /* By default, a peripheral configured to use an interrupt driven character

        queue transfer will have an infinite block time.  Lower the block time for

        reading and writing to ensure FreeRTOS_read() and FreeRTOS_write() calls

        will return, even in the presence of an error.  In this example, both

        the read and write block times are set to 100ms.  Again, for simplicity,

        this example does not show the return value being checked. */

        FreeRTOS_ioctl( xOpenedPort, ioctlSET_RX_TIMEOUT, ( void * ) ulMaxBlock100ms );

        FreeRTOS_ioctl( xOpenedPort, ioctlSET_TX_TIMEOUT, ( void * ) ulMaxBlock100ms );

        



        /***************** Use the port ***************************************/

        

        

        for( ;; )

        {

            /* Write 10 bytes from ucBuffer to the opened port.  Note the 

            definition of ucBuffer is assumed to be outside of this function. */

            xBytesTransferred = FreeRTOS_write( xOpenedPort, ucBuffer, 10 );

            

            /* At this point, 10 bytes will have been written to the Tx queue,

            but not necessarily written to the peripheral yet.  Check all 10 bytes

            were written to the queue - they should have been as the queue is

            20 bytes long. */

            configASSERT( xBytesTransferred == 10 );

            

            /* Read 10 bytes from the same port into ucBuffer.  Note, this will

            not read the bytes from the peripheral directly, but from the Rx 

            queue that is populated by the FreeRTOS-Plus-IO peripheral interrupt service

            routine.  The calling task is held in the Blocked state to wait

            for 10 bytes to become available if they are not available immediately,

            but the task will not be held in the Blocked state for more than 100ms. */

            xBytesTransferred = FreeRTOS_read( xOpenedPort, ucBuffer, 10 );

            

            if( xBytesTransferred == 10 )

            {

                /* Ten bytes were read from the peripheral before the 100ms block

                time expired. */

            }

            else

            {

                /* The block time must have expired before ten bytes could be

                read from the peripheral.  xBytesTransferred could be any value

                from 0 to 9. */

            }

        }

    }

    else

    {

        /* The port was not opened successfully. */

    }

}