simple-FreeRTOS-demo/serial/serialISR.c

   1 /*
   2     FreeRTOS V6.0.5 - Copyright (C) 2010 Real Time Engineers Ltd.
   3
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  24
  25     This file is part of the FreeRTOS distribution.
  26
  27     FreeRTOS is free software; you can redistribute it and/or modify it under
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  52 */
  53
  54
  55 /*
  56         BASIC INTERRUPT DRIVEN SERIAL PORT DRIVER FOR UART0.
  57
  58         This file contains all the serial port components that must be compiled
  59         to ARM mode.  The components that can be compiled to either ARM or THUMB
  60         mode are contained in serial.c.
  61
  62 */
  63
  64 /* Standard includes. */
  65 #include <stdlib.h>
  66
  67 /* Scheduler includes. */
  68 #include "FreeRTOS.h"
  69 #include "queue.h"
  70 #include "task.h"
  71
  72 /* Demo application includes. */
  73 #include "serial.h"
  74
  75 /*-----------------------------------------------------------*/
  76
  77 /* Constant to access the VIC. */
  78 #define serCLEAR_VIC_INTERRUPT                  ( ( unsigned long ) 0 )
  79
  80 /* Constants to determine the ISR source. */
  81 #define serSOURCE_THRE                                  ( ( unsigned char ) 0x02 )
  82 #define serSOURCE_RX_TIMEOUT                    ( ( unsigned char ) 0x0c )
  83 #define serSOURCE_ERROR                                 ( ( unsigned char ) 0x06 )
  84 #define serSOURCE_RX                                    ( ( unsigned char ) 0x04 )
  85 #define serINTERRUPT_SOURCE_MASK                ( ( unsigned char ) 0x0f )
  86
  87 /* Queues used to hold received characters, and characters waiting to be
  88 transmitted. */
  89 static xQueueHandle xRxedChars;
  90 static xQueueHandle xCharsForTx;
  91 static volatile long lTHREEmpty;
  92
  93 /*-----------------------------------------------------------*/
  94
  95 /*
  96  * The queues are created in serialISR.c as they are used from the ISR.
  97  * Obtain references to the queues and THRE Empty flag.
  98  */
  99 void vSerialISRCreateQueues( unsigned portBASE_TYPE uxQueueLength, xQueueHandle *pxRxedChars, xQueueHandle *pxCharsForTx, long volatile **pplTHREEmptyFlag );
 100
 101 /* UART0 interrupt service routine entry point. */
 102 void vUART_ISR_Wrapper( void ) __attribute__ ((naked));
 103
 104 /* UART0 interrupt service routine handler. */
 105 void vUART_ISR_Handler( void ) __attribute__ ((noinline));
 106
 107 /*-----------------------------------------------------------*/
 108 void vSerialISRCreateQueues(    unsigned portBASE_TYPE uxQueueLength, xQueueHandle *pxRxedChars,
 109                                                                 xQueueHandle *pxCharsForTx, long volatile **pplTHREEmptyFlag )
 110 {
 111         /* Create the queues used to hold Rx and Tx characters. */
 112         xRxedChars = xQueueCreate( uxQueueLength, ( unsigned portBASE_TYPE ) sizeof( signed char ) );
 113         xCharsForTx = xQueueCreate( uxQueueLength + 1, ( unsigned portBASE_TYPE ) sizeof( signed char ) );
 114
 115         /* Pass back a reference to the queues so the serial API file can
 116         post/receive characters. */
 117         *pxRxedChars = xRxedChars;
 118         *pxCharsForTx = xCharsForTx;
 119
 120         /* Initialise the THRE empty flag - and pass back a reference. */
 121         lTHREEmpty = ( long ) pdTRUE;
 122         *pplTHREEmptyFlag = &lTHREEmpty;
 123 }
 124 /*-----------------------------------------------------------*/
 125
 126 void vUART_ISR_Wrapper( void )
 127 {
 128         /* Save the context of the interrupted task. */
 129         portSAVE_CONTEXT();
 130
 131         /* Call the handler.  This must be a separate function from the wrapper
 132         to ensure the correct stack frame is set up. */
 133         __asm volatile ("bl vUART_ISR_Handler");
 134
 135         /* Restore the context of whichever task is going to run next. */
 136         portRESTORE_CONTEXT();
 137 }
 138 /*-----------------------------------------------------------*/
 139
 140 void vUART_ISR_Handler( void )
 141 {
 142 signed char cChar;
 143 portBASE_TYPE xHigherPriorityTaskWoken = pdFALSE;
 144
 145         /* What caused the interrupt? */
 146         switch( UART0_IIR & serINTERRUPT_SOURCE_MASK )
 147         {
 148                 case serSOURCE_ERROR :  /* Not handling this, but clear the interrupt. */
 149                                                                 cChar = UART0_LSR;
 150                                                                 break;
 151
 152                 case serSOURCE_THRE     :       /* The THRE is empty.  If there is another
 153                                                                 character in the Tx queue, send it now. */
 154                                                                 if( xQueueReceiveFromISR( xCharsForTx, &cChar, &xHigherPriorityTaskWoken ) == pdTRUE )
 155                                                                 {
 156                                                                         UART0_THR = cChar;
 157                                                                 }
 158                                                                 else
 159                                                                 {
 160                                                                         /* There are no further characters
 161                                                                         queued to send so we can indicate
 162                                                                         that the THRE is available. */
 163                                                                         lTHREEmpty = pdTRUE;
 164                                                                 }
 165                                                                 break;
 166
 167                 case serSOURCE_RX_TIMEOUT :
 168                 case serSOURCE_RX       :       /* A character was received.  Place it in
 169                                                                 the queue of received characters. */
 170                                                                 cChar = UART0_RBR;
 171                                                                 xQueueSendFromISR( xRxedChars, &cChar, &xHigherPriorityTaskWoken );
 172                                                                 break;
 173
 174                 default                         :       /* There is nothing to do, leave the ISR. */
 175                                                                 break;
 176         }
 177
 178         if( xHigherPriorityTaskWoken )
 179         {
 180                 portYIELD_FROM_ISR();
 181         }
 182
 183         /* Clear the ISR in the VIC. */
 184         VICVectAddr = serCLEAR_VIC_INTERRUPT;
 185 }
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