serial_isr.c

/*********************************************************************************

 Copyright 2006-2008 MakingThings

 Licensed under the Apache License, 
 Version 2.0 (the "License"); you may not use this file except in compliance 
 with the License. You may obtain a copy of the License at

 http://www.apache.org/licenses/LICENSE-2.0 
 
 Unless required by applicable law or agreed to in writing, software distributed
 under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
 CONDITIONS OF ANY KIND, either express or implied. See the License for
 the specific language governing permissions and limitations under the License.

*********************************************************************************/

/* 
  BASIC INTERRUPT DRIVEN DRIVER FOR SERIAL PORT. 

  This file contains all the 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

*/

/* Scheduler includes. */
#include "FreeRTOS.h"
#include "task.h"
#include "queue.h"
#include "semphr.h"
#include "Board.h"
#include "serial_internal.h"

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

extern Serial_ Serial[ SERIAL_PORTS ];

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

/* The interrupt entry point is naked so we can control the context saving. */
void SerialIsr_Wrapper( void ) __attribute__ ((naked));

/* The interrupt handler function must be separate from the entry function
to ensure the correct stack frame is set up. */
void SerialIsr_Handler( void );

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

void SerialIsr_Handler( void )
{
  unsigned portLONG ulStatus; 
  signed portCHAR cChar; 

  long xTaskWokenByTx = false; 
  long xTaskWokenByPost = false; 

  int index;
  for ( index = 0; index < SERIAL_PORTS; index++ )
  {
    long xTaskWokenByTxThis = false; 
    long xTaskWokenByPostThis = false; 
 
    Serial_* sp = &Serial[ index ];

    /* What caused the interrupt? */ 
    ulStatus = ( sp->at91UARTRegs->US_CSR ) & ( sp->at91UARTRegs->US_IMR ); 
   
    if( ulStatus & AT91C_US_TXRDY ) 
    { 
      /* The interrupt was caused by the THR becoming empty. Are there any 
         more characters to transmit? */ 
      if( xQueueReceiveFromISR( sp->transmitQueue, &cChar, &xTaskWokenByTx ) == pdTRUE ) 
      { 
        /* A character was retrieved from the queue so can be sent to the 
           THR now. */ 
        sp->at91UARTRegs->US_THR = cChar; 
      } 
      else 
      {    
        /* Queue empty, nothing to send so turn off the Tx interrupt. */ 
        sp->at91UARTRegs->US_IDR = AT91C_US_TXRDY; 
      }   
    } 
     
    if( ulStatus & AT91C_US_RXRDY ) 
    { 
      /* The interrupt was caused by a character being received. Grab the 
      character from the RHR and place it in the queue or received  
      characters. */ 
      int t = sp->at91UARTRegs->US_RHR;
      cChar = t & 0xFF; 
      xTaskWokenByPost = xQueueSendFromISR( sp->receiveQueue, &cChar, xTaskWokenByPost ); 
    }

    xTaskWokenByTx = xTaskWokenByTx || xTaskWokenByTxThis; 
    xTaskWokenByPost = xTaskWokenByPost || xTaskWokenByPostThis; 
  }
   
  /* End the interrupt in the AIC. */ 
  AT91C_BASE_AIC->AIC_EOICR = 0;

  /* If a task was woken by either a frame being received then we may need to 
  switch to another task.  If the unblocked task was of higher priority then
  the interrupted task it will then execute immediately that the ISR
  completes. */
  if( xTaskWokenByPost || xTaskWokenByTx )
  {
    portYIELD_FROM_ISR();
  }
}

void SerialIsr_Wrapper( void )
{
  /* Save the context of the interrupted task. */
  portSAVE_CONTEXT();

  /* Call the handler to do the work.  This must be a separate
  function to ensure the stack frame is set up correctly. */
  SerialIsr_Handler();

  /* Restore the context of whichever task will execute next. */
  portRESTORE_CONTEXT();
}

---

The Make Controller Kit is an open source project maintained by MakingThings.
MakingThings code is released under the Apache 2.0 license.
Bug tracker, development wiki and status can be found at http://dev.makingthings.com.
This document was last updated on 18 May 2009.