text: /*
   * FreeRTOS V202012.00
   * Copyright (C) 2020 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
   *
   * Permission is hereby granted, free of charge, to any person obtaining a copy of
   * this software and associated documentation files (the "Software"), to deal in
   * the Software without restriction, including without limitation the rights to
   * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
   * the Software, and to permit persons to whom the Software is furnished to do so,
   * subject to the following conditions:
   *
   * The above copyright notice and this permission notice shall be included in all
   * copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
   * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
   * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
   * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
   * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
   *
   * http://www.FreeRTOS.org
   * http://aws.amazon.com/freertos
   *
   * 1 tab == 4 spaces!
   */
  
  /*
  	BASIC INTERRUPT DRIVEN SERIAL PORT DRIVER FOR UART0.
  
  	*NOTE* - This file is designed to test some of the RTOS features - it is
  	not intended to represent an efficient implementation!
  */
  
  /* Standard includes. */
  #include <stdlib.h>
  
  /* Scheduler includes. */
  #include "FreeRTOS.h"
  #include "queue.h"
  
  /* Demo application includes. */
  #include "serial.h"
  
  
  /* Hardware specifics. */
  #define serRX_DATA_PIN		( 0x01 )
  #define serTX_DATA_PIN		( 0x02 )
  #define serCLOCK_Fxx_DIV_8		0x03
  #define serUPWR		( 0x80 )
  #define serUTXE		( 0x40 )
  #define serURXE		( 0x20 )
  #define serUCL		( 0x02 )
  #define serLSB		( 0x10 )
  
  /* Misc. */
  #define serINVALID_QUEUE				( ( QueueHandle_t ) 0 )
  #define serHANDLE						( ( xComPortHandle ) 1 )
  #define serNO_BLOCK						( ( TickType_t ) 0 )
  
  /*-----------------------------------------------------------*/
  
  /* Queues used to hold received characters, and characters waiting to be
  transmitted. */
  static QueueHandle_t xRxedChars;
  static QueueHandle_t xCharsForTx;
  
  /*-----------------------------------------------------------*/
  
  /* Interrupt entry point written in the assembler file serialISR.s85. */
  extern void vSerialISREntry( void );
  
  /* Flag to indicate whether or not there are characters already queued to send. */
  static volatile unsigned long ulTxInProgress = pdFALSE;
  
  /*-----------------------------------------------------------*/
  
  /*
   * See the serial2.h header file.
   */
  xComPortHandle xSerialPortInitMinimal( unsigned long ulWantedBaud, unsigned portBASE_TYPE uxQueueLength )
  {
  xComPortHandle xReturn = serHANDLE;
  const unsigned long ulFuclk = ( configCPU_CLOCK_HZ / 2 ) / 8UL;
  
  	/* Create the queues used to hold Rx and Tx characters. */
  	xRxedChars = xQueueCreate( uxQueueLength, ( unsigned portBASE_TYPE ) sizeof( signed char ) );
  	xCharsForTx = xQueueCreate( uxQueueLength + 1, ( unsigned portBASE_TYPE ) sizeof( signed char ) );
  
  	/* If the queues were created correctly then setup the serial port
  	hardware. */
  	if( ( xRxedChars != serINVALID_QUEUE ) && ( xCharsForTx != serINVALID_QUEUE ) )
  	{
  		portENTER_CRITICAL();
  		{
  			/* Set the UART0 Rx and Tx pins to their alternative function. */
  			PMC3 |= ( serRX_DATA_PIN | serTX_DATA_PIN );
  			PM3 &= ~( serTX_DATA_PIN );
  
  			/* Setup clock for required baud. */			
  			UD0CTL1 = serCLOCK_Fxx_DIV_8;
  			UD0CTL2 = ulFuclk / ( 2 * ulWantedBaud );
  
  			/* Enable, n81. */			
  			UD0CTL0 = ( serUPWR | serUTXE | serURXE | serUCL | serLSB );
  			
  			/* Enable interrupts for both Rx and Tx. */
  			UD0TIC  = 0x07;
  			UD0RIC  = 0x07;
  			
  			ulTxInProgress = pdFALSE;
  		}
  		portEXIT_CRITICAL();
  	}
  	else
  	{
  		xReturn = ( xComPortHandle ) 0;
  	}
  
  	/* This demo file only supports a single port but we have to return
  	something to comply with the standard demo header file. */
  	return xReturn;
  }
  /*-----------------------------------------------------------*/
  
  signed portBASE_TYPE xSerialGetChar( xComPortHandle pxPort, signed char *pcRxedChar, TickType_t xBlockTime )
  {
  	/* The port handle is not required as this driver only supports one port. */
  	( void ) pxPort;
  
  	/* Get the next character from the buffer.  Return false if no characters
  	are available, or arrive before xBlockTime expires. */
  	if( xQueueReceive( xRxedChars, pcRxedChar, xBlockTime ) )
  	{
  		return pdTRUE;
  	}
  	else
  	{
  		return pdFALSE;
  	}
  }
  /*-----------------------------------------------------------*/
  
  void vSerialPutString( xComPortHandle pxPort, const signed char * const pcString, unsigned short usStringLength )
  {
  signed char *pxNext;
  
  	/* A couple of parameters that this port does not use. */
  	( void ) usStringLength;
  	( void ) pxPort;
  
  	/* NOTE: This implementation does not handle the queue being full as no
  	block time is used! */
  
  	/* The port handle is not required as this driver only supports UART0. */
  	( void ) pxPort;
  
  	/* Send each character in the string, one at a time. */
  	pxNext = ( signed char * ) pcString;
  	while( *pxNext )
  	{
  		xSerialPutChar( pxPort, *pxNext, serNO_BLOCK );
  		pxNext++;
  	}
  }
  /*-----------------------------------------------------------*/
  
  signed portBASE_TYPE xSerialPutChar( xComPortHandle pxPort, signed char cOutChar, TickType_t xBlockTime )
  {
  portBASE_TYPE xReturn = pdPASS;
  
  	portENTER_CRITICAL();
  	{
  		/* There are currently no characters queued up to send so write the
  		character directly to the UART. */
  		if( ulTxInProgress == pdFALSE )
  		{
  			UD0TX = cOutChar;
  			ulTxInProgress = pdTRUE;
  		}
  		else
  		{
  			/* The UART is already busy so write the character to the Tx queue.
  			The queue is drained from within the Tx interrupt. */
  			if( xQueueSend( xCharsForTx, &cOutChar, xBlockTime ) != pdPASS )
  			{
  				xReturn = pdFAIL;
  			}
  		}
  	}
  	portEXIT_CRITICAL();
  	
  	return xReturn;
  }
  /*-----------------------------------------------------------*/
  
  void vSerialClose( xComPortHandle xPort )
  {
  	/* Not supported as not required by the demo application. */
  }
  /*-----------------------------------------------------------*/
  
  /* Tx interrupt handler.  This is called from the asm file wrapper. */
  void vUARTTxISRHandler( void )
  {
  char cChar;
  portBASE_TYPE xHigherPriorityTaskWoken = pdFALSE;
  
  	/* Are there any more characters queue to transmit? */
  	if( xQueueReceiveFromISR( xCharsForTx, &cChar, &xHigherPriorityTaskWoken ) == pdTRUE )
  	{
  		/* Send the next character. */
  		UD0TX = cChar;
  	}
  	else
  	{
  		/* The UART is no longer active. */
  		ulTxInProgress = pdFALSE;
  	}
  	
  	/* If reading a character from the Rx queue caused a task to unblock, and
  	the unblocked task has a priority higher than the currently running task,
  	then xHigherPriorityTaskWoken will have been set to true and a context
  	switch should occur now. */
  	portYIELD_FROM_ISR( xHigherPriorityTaskWoken );
  }
  /*-----------------------------------------------------------*/
  
  /* Rx interrupt handler.  This is called from the asm file wrapper. */
  void vUARTRxISRHandler( void )
  {
  char cChar;
  portBASE_TYPE xHigherPriorityTaskWoken = pdFALSE;
  
  	/* Send the received character to the Rx queue. */
  	cChar = UD0RX;
  	xQueueSendFromISR( xRxedChars, &cChar, &xHigherPriorityTaskWoken );
  	
  	/* If sending a character to the Tx queue caused a task to unblock, and
  	the unblocked task has a priority higher than the currently running task,
  	then xHigherPriorityTaskWoken will have been set to true and a context
  	switch should occur now. */
  	portYIELD_FROM_ISR( xHigherPriorityTaskWoken );	
  }
  
  
  
  
  	
  