轮询传输模式

[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 xBytesTransferred;



    /* 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 )

    {

        /* 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, so 

        the following FreeRTOS_write() call will write 10 bytes from the 

        ucBuffer array to the SPI2 peripheral.  The ucBuffer declaration is not 

        shown, and assumed to be outside of this example function. */

        xBytesTransferred = FreeRTOS_write( xOpenedPort, ucBuffer, 10 );

        

        /* As polled mode is being used, xBytesTransferred should be 10, unless

        an error occurred. */

        configASSERT( xBytesTransferred == 10 );

        

        /* The transfer mode has not been changed, so the following read will

        also use polled mode.  It will read 10 bytes into ucBuffer. */

        xBytesTransferred = FreeRTOS_read( xOpenedPort, ucBuffer, 10 );

        

        /* Again, as polled mode is used, the call to FreeRTOS_read() will have

        returned all of the 10 requested bytes unless an error occurred. */

        configASSERT( xBytesTransferred == 10 );

    }

    else

    {

        /* The port was not opened successfully. */

    }

}