text: /*
      FreeRTOS V7.1.1 - Copyright (C) 2012 Real Time Engineers Ltd.
  	
  
      ***************************************************************************
       *                                                                       *
       *    FreeRTOS tutorial books are available in pdf and paperback.        *
       *    Complete, revised, and edited pdf reference manuals are also       *
       *    available.                                                         *
       *                                                                       *
       *    Purchasing FreeRTOS documentation will not only help you, by       *
       *    ensuring you get running as quickly as possible and with an        *
       *    in-depth knowledge of how to use FreeRTOS, it will also help       *
       *    the FreeRTOS project to continue with its mission of providing     *
       *    professional grade, cross platform, de facto standard solutions    *
       *    for microcontrollers - completely free of charge!                  *
       *                                                                       *
       *    >>> See http://www.FreeRTOS.org/Documentation for details. <<<     *
       *                                                                       *
       *    Thank you for using FreeRTOS, and thank you for your support!      *
       *                                                                       *
      ***************************************************************************
  
  
      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 modification to the GPL is included to allow you to
      distribute a combined work that includes FreeRTOS without being obliged to
      provide the source code for proprietary components outside of the FreeRTOS
      kernel.  FreeRTOS is distributed in the hope that it will be useful, but
      WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
      or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
      more details. You should have received a copy of the GNU General Public
      License and the FreeRTOS license exception along with FreeRTOS; if not it
      can be viewed here: http://www.freertos.org/a00114.html and also obtained
      by writing to Richard Barry, contact details for whom are available on the
      FreeRTOS WEB site.
  
      1 tab == 4 spaces!
      
      ***************************************************************************
       *                                                                       *
       *    Having a problem?  Start by reading the FAQ "My application does   *
       *    not run, what could be wrong?                                      *
       *                                                                       *
       *    http://www.FreeRTOS.org/FAQHelp.html                               *
       *                                                                       *
      ***************************************************************************
  
      
      http://www.FreeRTOS.org - Documentation, training, latest information, 
      license and contact details.
      
      http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
      including FreeRTOS+Trace - an indispensable productivity tool.
  
      Real Time Engineers ltd license FreeRTOS to High Integrity Systems, who sell 
      the code with commercial support, indemnification, and middleware, under 
      the OpenRTOS brand: http://www.OpenRTOS.com.  High Integrity Systems also
      provide a safety engineered and independently SIL3 certified version under 
      the SafeRTOS brand: http://www.SafeRTOS.com.
  */
  
  
  /*
   * Creates a task and a timer that operate on an interrupt driven serial port.
   * This demo assumes that the characters transmitted on a port will also be
   * received on the same port.  Therefore, the UART must either be connected to
   * an echo server, or the uart connector must have a loopback connector fitted.
   * See http://www.serialporttool.com/CommEcho.htm for a suitable echo server
   * for Windows hosts.
   *
   * The timer sends a string to the UART, toggles an LED, then resets itself by 
   * changing its own period.  The period is calculated as a pseudo random number 
   * between comTX_MAX_BLOCK_TIME and comTX_MIN_BLOCK_TIME.
   *
   * The task blocks on an Rx queue waiting for a character to become available.  
   * Received characters are checked to ensure they match those transmitted by the 
   * Tx timer.  An error is latched if characters are missing, incorrect, or 
   * arrive too slowly.
   *
   * How characters are actually transmitted and received is port specific.  Demos
   * that include this test/demo file will provide example drivers.  The Tx timer
   * executes in the context of the timer service (daemon) task, and must 
   * therefore never attempt to block.
   *
   */
  
  /* Scheduler include files. */
  #include <stdlib.h>
  #include <string.h>
  #include "FreeRTOS.h"
  #include "task.h"
  #include "timers.h"
  
  #ifndef configUSE_TIMERS
  	#error This demo uses timers.  configUSE_TIMERS must be set to 1 in FreeRTOSConfig.h.
  #endif
  
  #if configUSE_TIMERS != 1
  	#error This demo uses timers.  configUSE_TIMERS must be set to 1 in FreeRTOSConfig.h.
  #endif
  
  
  /* Demo program include files. */
  #include "serial.h"
  #include "comtest_strings.h"
  #include "partest.h"
  
  /* The size of the stack given to the Rx task. */
  #define comSTACK_SIZE				configMINIMAL_STACK_SIZE
  
  /* See the comment above the declaraction of the uxBaseLED variable. */
  #define comTX_LED_OFFSET			( 0 )
  #define comRX_LED_OFFSET			( 1 )
  
  /* The Tx timer transmits the sequence of characters at a pseudo random
  interval that is capped between comTX_MAX_BLOCK_TIME and
  comTX_MIN_BLOCK_TIME. */
  #define comTX_MAX_BLOCK_TIME		( ( portTickType ) 0x96 )
  #define comTX_MIN_BLOCK_TIME		( ( portTickType ) 0x32 )
  #define comOFFSET_TIME				( ( portTickType ) 3 )
  
  /* States for the simple state machine implemented in the Rx task. */
  #define comtstWAITING_START_OF_STRING 	0
  #define comtstWAITING_END_OF_STRING		1
  
  /* A short delay in ticks - this delay is used to allow the Rx queue to fill up
  a bit so more than one character can be processed at a time.  This is relative
  to comTX_MIN_BLOCK_TIME to ensure it is never longer than the shortest gap
  between transmissions.  It could be worked out more scientifically from the
  baud rate being used. */
  #define comSHORT_DELAY				( comTX_MIN_BLOCK_TIME >> ( portTickType ) 2 )
  
  /* The string that is transmitted and received. */
  #define comTRANSACTED_STRING		"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890"
  
  /* A block time of 0 simply means "don't block". */
  #define comtstDONT_BLOCK			( portTickType ) 0
  
  /* Handle to the com port used by both tasks. */
  static xComPortHandle xPort = NULL;
  
  /* The callback function allocated to the transmit timer, as described in the
  comments at the top of this file. */
  static void prvComTxTimerCallback( xTimerHandle xTimer );
  
  /* The receive task as described in the comments at the top of this file. */
  static void vComRxTask( void *pvParameters );
  
  /* The Rx task will toggle LED ( uxBaseLED + comRX_LED_OFFSET).  The Tx task
  will toggle LED ( uxBaseLED + comTX_LED_OFFSET ). */
  static unsigned portBASE_TYPE uxBaseLED = 0;
  
  /* The Rx task toggles uxRxLoops on each successful iteration of its defined
  function - provided no errors have ever been latched.  If this variable stops
  incrementing, then an error has occurred. */
  static volatile unsigned portBASE_TYPE uxRxLoops = 0UL;
  
  /* The timer used to periodically transmit the string.  This is the timer that
  has prvComTxTimerCallback allocated to it as its callback function. */
  static xTimerHandle xTxTimer = NULL;
  
  /* The string length is held at file scope so the Tx timer does not need to
  calculate it each time it executes. */
  static size_t xStringLength = 0U;
  
  /*-----------------------------------------------------------*/
  
  void vStartComTestStringsTasks( unsigned portBASE_TYPE uxPriority, unsigned long ulBaudRate, unsigned portBASE_TYPE uxLED )
  {
  	/* Store values that are used at run time. */
  	uxBaseLED = uxLED;
  
  	/* Calculate the string length here, rather than each time the Tx timer
  	executes. */
  	xStringLength = strlen( comTRANSACTED_STRING );
  
  	/* Include the null terminator in the string length as this is used to
  	detect the end of the string in the Rx task. */
  	xStringLength++;
  
  	/* Initialise the com port, then spawn the Rx task and create the Tx
  	timer. */
  	xSerialPortInitMinimal( ulBaudRate, ( xStringLength * 2U ) );
  
  	/* Create the Rx task and the Tx timer.  The timer is started from the
  	Rx task. */
  	xTaskCreate( vComRxTask, ( signed char * ) "COMRx", comSTACK_SIZE, NULL, uxPriority, ( xTaskHandle * ) NULL );
  	xTxTimer = xTimerCreate( ( const signed char * ) "TxTimer", comTX_MIN_BLOCK_TIME, pdFALSE, NULL, prvComTxTimerCallback );
  	configASSERT( xTxTimer );
  }
  /*-----------------------------------------------------------*/
  
  static void prvComTxTimerCallback( xTimerHandle xTimer )
  {
  portTickType xTimeToWait;
  
  	/* The parameter is not used in this case. */
  	( void ) xTimer;
  
  	/* Send the string.  How this is actually performed depends on the
  	sample driver provided with this demo.  However - as this is a timer,
  	it executes in the context of the timer task and therefore must not
  	block. */
  	vSerialPutString( xPort, ( const signed char * const ) comTRANSACTED_STRING, xStringLength );
  
  	/* Toggle an LED to give a visible indication that another transmission
  	has been performed. */
  	vParTestToggleLED( uxBaseLED + comTX_LED_OFFSET );
  
  	/* Wait a pseudo random time before sending the string again. */
  	xTimeToWait = xTaskGetTickCount() + comOFFSET_TIME;
  
  	/* Ensure the time to wait is not greater than comTX_MAX_BLOCK_TIME. */
  	xTimeToWait %= comTX_MAX_BLOCK_TIME;
  
  	/* Ensure the time to wait is not less than comTX_MIN_BLOCK_TIME. */
  	if( xTimeToWait < comTX_MIN_BLOCK_TIME )
  	{
  		xTimeToWait = comTX_MIN_BLOCK_TIME;
  	}
  
  	/* Reset the timer to run again xTimeToWait ticks from now.  This function
  	is called from the context of the timer task, so the block time must not
  	be anything other than zero. */
  	xTimerChangePeriod( xTxTimer, xTimeToWait, comtstDONT_BLOCK );
  }
  /*-----------------------------------------------------------*/
  
  static void vComRxTask( void *pvParameters )
  {
  portBASE_TYPE xState = comtstWAITING_START_OF_STRING, xErrorOccurred = pdFALSE;
  signed char *pcExpectedByte, cRxedChar;
  const xComPortHandle xPort = NULL;
  
  	/* The parameter is not used in this example. */
  	( void ) pvParameters;
  
  	/* Start the Tx timer.  This only needs to be started once, as it will
  	reset itself thereafter. */
  	xTimerStart( xTxTimer, portMAX_DELAY );
  
  	/* The first expected Rx character is the first in the string that is
  	transmitted. */
  	pcExpectedByte = ( signed char * ) comTRANSACTED_STRING;
  
  	for( ;; )
  	{
  		/* Wait for the next character. */
  		if( xSerialGetChar( xPort, &cRxedChar, ( comTX_MAX_BLOCK_TIME * 2 ) ) == pdFALSE )
  		{
  			/* A character definitely should have been received by now.  As a
  			character was not received an error must have occurred (which might
  			just be that the loopback connector is not fitted). */
  			xErrorOccurred = pdTRUE;
  		}
  
  		switch( xState )
  		{
  			case comtstWAITING_START_OF_STRING:
  				if( cRxedChar == *pcExpectedByte )
  				{
  					/* The received character was the first character of the
  					string.  Move to the next state to check each character
  					as it comes in until the entire string has been received. */
  					xState = comtstWAITING_END_OF_STRING;
  					pcExpectedByte++;
  
  					/* Block for a short period.  This just allows the Rx queue 
  					to contain more than one character, and therefore prevent
  					thrashing reads to the queue, and repetitive context 
  					switches as	each character is received. */
  					vTaskDelay( comSHORT_DELAY );
  				}
  				break;
  
  			case comtstWAITING_END_OF_STRING:
  				if( cRxedChar == *pcExpectedByte )
  				{
  					/* The received character was the expected character.  Was
  					it the last character in the string - i.e. the null
  					terminator? */
  					if( cRxedChar == 0x00 )
  					{
  						/* The entire string has been received.  If no errors
  						have been latched, then increment the loop counter to
  						show this task is still healthy. */
  						if( xErrorOccurred == pdFALSE )
  						{
  							uxRxLoops++;
  
  							/* Toggle an LED to give a visible sign that a
  							complete string has been received. */
  							vParTestToggleLED( uxBaseLED + comRX_LED_OFFSET );
  						}
  
  						/* Go back to wait for the start of the next string. */
  						pcExpectedByte = ( signed char * ) comTRANSACTED_STRING;
  						xState = comtstWAITING_START_OF_STRING;
  					}
  					else
  					{
  						/* Wait for the next character in the string. */
  						pcExpectedByte++;
  					}
  				}
  				else
  				{
  					/* The character received was not that expected. */
  					xErrorOccurred = pdTRUE;
  				}
  				break;
  
  			default:
  				/* Should not get here.  Stop the Rx loop counter from
  				incrementing to latch the error. */
  				xErrorOccurred = pdTRUE;
  				break;
  		}
  	}
  }
  /*-----------------------------------------------------------*/
  
  portBASE_TYPE xAreComTestTasksStillRunning( void )
  {
  portBASE_TYPE xReturn;
  
  	/* If the count of successful reception loops has not changed than at
  	some time an error occurred (i.e. a character was received out of sequence)
  	and false is returned. */
  	if( uxRxLoops == 0UL )
  	{
  		xReturn = pdFALSE;
  	}
  	else
  	{
  		xReturn = pdTRUE;
  	}
  
  	/* Reset the count of successful Rx loops.  When this function is called
  	again it should have been incremented again. */
  	uxRxLoops = 0UL;
  
  	return xReturn;
  }
  
  