开发环境：mplab 3.45 harmony 1.09 xc32 1.42

源代码下载：/zixunimg/eeworldimg/download.csdn.net/detail/zn2857/9712707

源代码分析：

void APP_Tasks ( void )

{

/* Check the application's current state. */

switch ( appData.state )

{

/* Application's initial state. */

case APP_STATE_INIT:

{

bool appInitialized = true;

if (appInitialized)

{

/* Open the USART Driver for USART1 Client */

appData.drvUartHandle = DRV_USART_Open( DRV_USART_INDEX_0,DRV_IO_INTENT_READWRITE );

appData.state = APP_STATE_CHECK_DRVR_STATE;

}

break;

}

case APP_STATE_CHECK_DRVR_STATE:

{

/* Check the USART1 driver handler */

if (appData.drvUartHandle == DRV_HANDLE_INVALID )

{

/* Set the uart state to Ready */

appData.state = APP_STATE_INIT;

return;

}

DRV_USART_ByteReceiveCallbackSet(DRV_USART_INDEX_0, (DRV_USART_BYTE_EVENT_HANDLER)Uart_LoopBack);

appData.state = APP_STATE_IDLE;

break;

}

case APP_STATE_SERVICE_TASKS:

{

uint8_t numBytes = 0;

while( numBytes < 1 )

{

numBytes++;

if( !(DRV_USART_TRANSFER_STATUS_TRANSMIT_FULL & DRV_USART_TransferStatus(appData.drvUartHandle)) )

{

DRV_USART_WriteByte(appData.drvUartHandle, temp);

}

}

appData.state = APP_STATE_IDLE;

break;

}

case APP_STATE_IDLE:

{

break;

}

/* TODO: implement your application state machine.*/

/* The default state should never be executed. */

default:

{

/* TODO: Handle error in application's state machine. */

break;

}

}

}