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/*

    FreeRTOS V6.1.1 - Copyright (C) 2011 Real Time Engineers Ltd.

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    This file is part of the FreeRTOS distribution.

    FreeRTOS is free software; you can redistribute it and/or modify it under

    the terms of the GNU General Public License (version 2) as published by the

    Free Software Foundation AND MODIFIED BY the FreeRTOS exception.

    ***NOTE*** The exception to the GPL is included to allow you to distribute

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*/

/*

  BASIC INTERRUPT DRIVEN SERIAL PORT DRIVER FOR USART0.

  This file contains all the serial port components that must be compiled

  to ARM mode.  The components that can be compiled to either ARM or THUMB

  mode are contained in serial.c.

*/

/* Standard includes. */

#include <stdlib.h>

/* Scheduler includes. */

#include "FreeRTOS.h"

#include "queue.h"

#include "task.h"

/* Demo application includes. */

#include "serial.h"

#include "AT91R40008.h"

#include "usart.h"

/*-----------------------------------------------------------*/

/* Constant to access the AIC. */

#define serCLEAR_AIC_INTERRUPT      ( ( unsigned long ) 0 )

/* Constants to determine the ISR source. */

#define serSOURCE_THRE                          ( ( unsigned char ) 0x02 )

#define serSOURCE_RX_TIMEOUT            ( ( unsigned char ) 0x0c )

#define serSOURCE_ERROR                         ( ( unsigned char ) 0x06 )

#define serSOURCE_RX                            ( ( unsigned char ) 0x04 )

#define serINTERRUPT_SOURCE_MASK    ( ( unsigned long ) (US_RXRDY | US_TXRDY | US_RXBRK | US_OVRE | US_FRAME | US_PARE) )

/* Queues used to hold received characters, and characters waiting to be

transmitted. */

static xQueueHandle xRxedChars;

static xQueueHandle xCharsForTx;

/*-----------------------------------------------------------*/

/* UART0 interrupt service routine.  This can cause a context switch so MUST

be declared "naked". */

void vUART_ISR_Wrapper( void ) __attribute__ ((naked));

/* The ISR function that actually performs the work.  This must be separate

from the wrapper to ensure the correct stack frame is set up. */

void vUART_ISR_Handler( void ) __attribute__ ((noinline));

/*-----------------------------------------------------------*/

void vSerialISRCreateQueues( unsigned portBASE_TYPE uxQueueLength, xQueueHandle *pxRxedChars, xQueueHandle *pxCharsForTx )

{

        /* Create the queues used to hold Rx and Tx characters. */

        xRxedChars = xQueueCreate( uxQueueLength, ( unsigned portBASE_TYPE ) sizeof( signed char ) );

        xCharsForTx = xQueueCreate( uxQueueLength + 1, ( unsigned portBASE_TYPE ) sizeof( signed char ) );

        /* Pass back a reference to the queues so the serial API file can

        post/receive characters. */

        *pxRxedChars = xRxedChars;

        *pxCharsForTx = xCharsForTx;

}

/*-----------------------------------------------------------*/

void vUART_ISR_Wrapper( void )

{

        /* Save the context of the interrupted task. */

        portSAVE_CONTEXT();

        /* Call the handler.  This must be a separate function to ensure the

        stack frame is correctly set up. */

        __asm volatile( "bl vUART_ISR_Handler" );

        /* Restore the context of whichever task will run next. */

        portRESTORE_CONTEXT();

}

/*-----------------------------------------------------------*/

void vUART_ISR_Handler( void )

{

/* Now we can declare the local variables.   These must be static. */

signed char cChar;

portBASE_TYPE xHigherPriorityTaskWoken = pdFALSE;

unsigned long ulStatus;

        /* What caused the interrupt? */

        ulStatus = AT91C_BASE_US0->US_CSR & AT91C_BASE_US0->US_IMR;

        if (ulStatus & US_TXRDY)

        {

                /* The interrupt was caused by the THR becoming empty.  Are there any

                more characters to transmit? */

                if( xQueueReceiveFromISR( xCharsForTx, &cChar, &xHigherPriorityTaskWoken ) == pdTRUE )

                {

                        /* A character was retrieved from the queue so can be sent to the

                        THR now. */

                        AT91C_BASE_US0->US_THR = cChar;

                }

                else

                {

                        /* Queue empty, nothing to send so turn off the Tx interrupt. */

                        AT91C_BASE_US0->US_IDR = US_TXRDY;

                }

        }

        if (ulStatus & US_RXRDY)

        {

                /* The interrupt was caused by the receiver getting data. */

                cChar = AT91C_BASE_US0->US_RHR;

                xQueueSendFromISR(xRxedChars, &cChar, &xHigherPriorityTaskWoken);

        }

        /* Acknowledge the interrupt at AIC level... */

        AT91C_BASE_AIC->AIC_EOICR = serCLEAR_AIC_INTERRUPT;

        /* If an event caused a task to unblock then we call "Yield from ISR" to

        ensure that the unblocked task is the task that executes when the interrupt

        completes if the unblocked task has a priority higher than the interrupted

        task. */

        if( xHigherPriorityTaskWoken )

        {

                portYIELD_FROM_ISR();

        }

}

/*-----------------------------------------------------------*/