中断驱动的循环缓冲区传输模式

[FreeRTOS-Plus-IO 传输模式]

/* FreeRTO+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 recommneded 

    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 the interrupt driven circular buffer

        transfer mode for reading.  The third FreeRTOS_ioctl() parameter sets the

        buffer length.   In this example, the length is set to 20.  A successful 

        FreeRTOS_ioctl() call will return pdPASS, for simplicity, this example 

        does not show the return value being checked. */

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

                

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

        buffer transfer will have an infinite block time.  Lower the block time

        to ensure FreeRTOS_read() calls will return, even in the presense of an 

        error.  In this example the read block time is set to 100ms.  Again, for 

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

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

        



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

        

        

        for( ;; )

        {

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

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

            buffer 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. 

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

            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. */

    }

}