FreeRTOS/Demo/Common/Full/comtest.c

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/**
 * Creates two tasks that operate on an interrupt driven serial port.  A loopback 
 * connector should be used so that everything that is transmitted is also received.  
 * The serial port does not use any flow control.  On a standard 9way 'D' connector 
 * pins two and three should be connected together.
 *
 * The first task repeatedly sends a string to a queue, character at a time.  The 
 * serial port interrupt will empty the queue and transmit the characters.  The 
 * task blocks for a pseudo random period before resending the string.
 *
 * The second task blocks on a queue waiting for a character to be received.  
 * Characters received by the serial port interrupt routine are posted onto the 
 * queue - unblocking the task making it ready to execute.  If this is then the 
 * highest priority task ready to run it will run immediately - with a context 
 * switch occurring at the end of the interrupt service routine.  The task 
 * receiving characters is spawned with a higher priority than the task 
 * transmitting the characters.
 *
 * With the loop back connector in place, one task will transmit a string and the 
 * other will immediately receive it.  The receiving task knows the string it 
 * expects to receive so can detect an error.
 *
 * This also creates a third task.  This is used to test semaphore usage from an
 * ISR and does nothing interesting.  
 * 
 * \page ComTestC comtest.c
 * \ingroup DemoFiles
 * <HR>
 */

/*
Changes from V1.00:
	
	+ The priority of the Rx task has been lowered.  Received characters are
	  now processed (read from the queue) at the idle priority, allowing low
	  priority tasks to run evenly at times of a high communications overhead.

Changes from V1.01:

	+ The Tx task now waits a pseudo random time between transissions.
	  Previously a fixed period was used but this was not such a good test as
	  interrupts fired at regular intervals.

Changes From V1.2.0:

	+ Use vSerialPutString() instead of single character puts.
	+ Only stop the check variable incrementing after two consecutive errors. 

Changed from V1.2.5

	+ Made the Rx task 2 priorities higher than the Tx task.  Previously it was
	  only 1.  This is done to tie in better with the other demo application 
	  tasks.

Changes from V2.0.0

	+ Delay periods are now specified using variables and constants of
	  TickType_t rather than unsigned long.
	+ Slight modification to task priorities.

*/


/* Scheduler include files. */
#include <stdlib.h>
#include <string.h>
#include "FreeRTOS.h"
#include "task.h"

/* Demo program include files. */
#include "serial.h"
#include "comtest.h"
#include "print.h"

/* The Tx task will transmit the sequence of characters at a pseudo random
interval.  This is the maximum and minimum block time between sends. */
#define comTX_MAX_BLOCK_TIME		( ( TickType_t ) 0x15e )
#define comTX_MIN_BLOCK_TIME		( ( TickType_t ) 0xc8 )

#define comMAX_CONSECUTIVE_ERRORS	( 2 )

#define comSTACK_SIZE				( ( unsigned short ) 256 )

#define comRX_RELATIVE_PRIORITY		( 1 )

/* Handle to the com port used by both tasks. */
static xComPortHandle xPort;

/* The transmit function as described at the top of the file. */
static void vComTxTask( void *pvParameters );

/* The receive function as described at the top of the file. */
static void vComRxTask( void *pvParameters );

/* The semaphore test function as described at the top of the file. */
static void vSemTestTask( void * pvParameters );

/* The string that is repeatedly transmitted. */
const char * const pcMessageToExchange = 	"Send this message over and over again to check communications interrupts. "
									   			"0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ\r\n";

/* Variables that are incremented on each cycle of each task.  These are used to 
check that both tasks are still executing. */
volatile short sTxCount = 0, sRxCount = 0, sSemCount = 0;

/* The handle to the semaphore test task. */
static TaskHandle_t xSemTestTaskHandle = NULL;

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

void vStartComTestTasks( unsigned portBASE_TYPE uxPriority, eCOMPort ePort, eBaud eBaudRate )
{
const unsigned portBASE_TYPE uxBufferLength = 255;

	/* Initialise the com port then spawn both tasks. */
	xPort = xSerialPortInit( ePort, eBaudRate, serNO_PARITY, serBITS_8, serSTOP_1, uxBufferLength );
	xTaskCreate( vComTxTask, "COMTx", comSTACK_SIZE, NULL, uxPriority, NULL );
	xTaskCreate( vComRxTask, "COMRx", comSTACK_SIZE, NULL, uxPriority + comRX_RELATIVE_PRIORITY, NULL );
	xTaskCreate( vSemTestTask, "ISRSem", comSTACK_SIZE, NULL, tskIDLE_PRIORITY, &xSemTestTaskHandle );
}
/*-----------------------------------------------------------*/

static void vComTxTask( void *pvParameters )
{
const char * const pcTaskStartMsg = "COM Tx task started.\r\n";
TickType_t xTimeToWait;

	/* Stop warnings. */
	( void ) pvParameters;

	/* Queue a message for printing to say the task has started. */
	vPrintDisplayMessage( &pcTaskStartMsg );

	for( ;; )
	{
		/* Send the string to the serial port. */
		vSerialPutString( xPort, pcMessageToExchange, strlen( pcMessageToExchange ) );

		/* We have posted all the characters in the string - increment the variable 
		used to check that this task is still running, then wait before re-sending 
		the string. */
		sTxCount++;

		xTimeToWait = xTaskGetTickCount();

		/* Make sure we don't wait too long... */
		xTimeToWait %= comTX_MAX_BLOCK_TIME;

		/* ...but we do want to wait. */
		if( xTimeToWait < comTX_MIN_BLOCK_TIME )
		{
			xTimeToWait = comTX_MIN_BLOCK_TIME;
		}

		vTaskDelay( xTimeToWait );
	}
} /*lint !e715 !e818 pvParameters is required for a task function even if it is not referenced. */
/*-----------------------------------------------------------*/

static void vComRxTask( void *pvParameters )
{
const char * const pcTaskStartMsg = "COM Rx task started.\r\n";
const char * const pcTaskErrorMsg = "COM read error\r\n";
const char * const pcTaskRestartMsg = "COM resynced\r\n";
const char * const pcTaskTimeoutMsg = "COM Rx timed out\r\n";
const TickType_t xBlockTime = ( TickType_t ) 0xffff / portTICK_PERIOD_MS;
const char *pcExpectedChar;
portBASE_TYPE xGotChar;
char cRxedChar;
short sResyncRequired, sConsecutiveErrors, sLatchedError;

	/* Stop warnings. */
	( void ) pvParameters;

	/* Queue a message for printing to say the task has started. */
	vPrintDisplayMessage( &pcTaskStartMsg );
	
	/* The first expected character is the first character in the string. */
	pcExpectedChar = pcMessageToExchange;
	sResyncRequired = pdFALSE;
	sConsecutiveErrors = 0;
	sLatchedError = pdFALSE;

	for( ;; )
	{
		/* Receive a message from the com port interrupt routine.  If a message is 
		not yet available the call will block the task. */
		xGotChar = xSerialGetChar( xPort, &cRxedChar, xBlockTime );
		if( xGotChar == pdTRUE )
		{
			if( sResyncRequired == pdTRUE )
			{
				/* We got out of sequence and are waiting for the start of the next 
				transmission of the string. */
				if( cRxedChar == '\n' )
				{
					/* This is the end of the message so we can start again - with 
					the first character in the string being the next thing we expect 
					to receive. */
					pcExpectedChar = pcMessageToExchange;
					sResyncRequired = pdFALSE;

					/* Queue a message for printing to say that we are going to try 
					again. */
					vPrintDisplayMessage( &pcTaskRestartMsg );

					/* Stop incrementing the check variable, if consecutive errors occur. */
					sConsecutiveErrors++;
					if( sConsecutiveErrors >= comMAX_CONSECUTIVE_ERRORS )
					{
						sLatchedError = pdTRUE;
					}
				}
			}
			else
			{
				/* We have received a character, but is it the expected character? */
				if( cRxedChar != *pcExpectedChar )
				{
					/* This was not the expected character so post a message for 
					printing to say that an error has occurred.  We will then wait 
					to resynchronise. */
					vPrintDisplayMessage( &pcTaskErrorMsg );					
					sResyncRequired = pdTRUE;
				}
				else
				{
					/* This was the expected character so next time we will expect 
					the next character in the string.  Wrap back to the beginning 
					of the string when the null terminator has been reached. */
					pcExpectedChar++;
					if( *pcExpectedChar == '\0' )
					{
						pcExpectedChar = pcMessageToExchange;

						/* We have got through the entire string without error. */
						sConsecutiveErrors = 0;
					}
				}
			}

			/* Increment the count that is used to check that this task is still 
			running.  This is only done if an error has never occurred. */
			if( sLatchedError == pdFALSE )
			{
				sRxCount++;			
			}
		}
		else
		{
			vPrintDisplayMessage( &pcTaskTimeoutMsg );
		}
	}
} /*lint !e715 !e818 pvParameters is required for a task function even if it is not referenced. */
/*-----------------------------------------------------------*/

static void vSemTestTask( void * pvParameters )
{
const char * const pcTaskStartMsg = "ISR Semaphore test started.\r\n";
portBASE_TYPE xError = pdFALSE;

 	/* Stop warnings. */
	( void ) pvParameters;

	/* Queue a message for printing to say the task has started. */
	vPrintDisplayMessage( &pcTaskStartMsg );

	for( ;; )
	{
		if( xSerialWaitForSemaphore( xPort ) )
		{
			if( xError == pdFALSE )
			{
				sSemCount++;
			}
		}
		else
		{
			xError = pdTRUE;
		}
	}
} /*lint !e715 !e830 !e818 pvParameters not used but function prototype must be standard for task function. */
/*-----------------------------------------------------------*/

/* This is called to check that all the created tasks are still running. */
portBASE_TYPE xAreComTestTasksStillRunning( void )
{
static short sLastTxCount = 0, sLastRxCount = 0, sLastSemCount = 0;
portBASE_TYPE xReturn;

	/* Not too worried about mutual exclusion on these variables as they are 16 
	bits and we are only reading them.  We also only care to see if they have 
	changed or not. */

	if( ( sTxCount == sLastTxCount ) || ( sRxCount == sLastRxCount ) || ( sSemCount == sLastSemCount ) )
	{
		xReturn = pdFALSE;
	}
	else
	{
		xReturn = pdTRUE;
	}

	sLastTxCount = sTxCount;
	sLastRxCount = sRxCount;
	sLastSemCount = sSemCount;

	return xReturn;
}
/*-----------------------------------------------------------*/

void vComTestUnsuspendTask( void )
{
	/* The task that is suspended on the semaphore will be referenced from the
	Suspended list as it is blocking indefinitely.  This call just checks that
	the kernel correctly detects this and does not attempt to unsuspend the
	task. */
	xTaskResumeFromISR( xSemTestTaskHandle );
}