/* | |
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*************************************************************************** | |
* * | |
* Get the FreeRTOS eBook! See http://www.FreeRTOS.org/Documentation * | |
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* This is a concise, step by step, 'hands on' guide that describes both * | |
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* explains numerous examples that are written using the FreeRTOS API. * | |
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* .zip file. * | |
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*************************************************************************** | |
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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 portLONG ) 0 ) | |
/* Constants to determine the ISR source. */ | |
#define serSOURCE_THRE ( ( unsigned portCHAR ) 0x02 ) | |
#define serSOURCE_RX_TIMEOUT ( ( unsigned portCHAR ) 0x0c ) | |
#define serSOURCE_ERROR ( ( unsigned portCHAR ) 0x06 ) | |
#define serSOURCE_RX ( ( unsigned portCHAR ) 0x04 ) | |
#define serINTERRUPT_SOURCE_MASK ( ( unsigned portLONG ) (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 ); | |
/*-----------------------------------------------------------*/ | |
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 portCHAR ) ); | |
xCharsForTx = xQueueCreate( uxQueueLength + 1, ( unsigned portBASE_TYPE ) sizeof( signed portCHAR ) ); | |
/* 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. */ | |
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 portCHAR cChar; | |
portBASE_TYPE xHigherPriorityTaskWoken = pdFALSE; | |
unsigned portLONG 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(); | |
} | |
} | |
/*-----------------------------------------------------------*/ | |