text: /*
   * FreeRTOS Kernel V10.3.1
   * 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 IAR AVR PORT. */
  
  #include <stdlib.h>
  #include "FreeRTOS.h"
  #include "queue.h"
  #include "task.h"
  #include "serial.h"
  #include <avr/interrupt.h>
  
  #define USART_BAUD_RATE(BAUD_RATE) ((float)(configCPU_CLOCK_HZ * 64 / (16 * (float)BAUD_RATE)) + 0.5)
   
  static QueueHandle_t xRxedChars;
  static QueueHandle_t xCharsForTx;
  
  #define vInterruptOn() USART3.CTRLA |= (1 << USART_DREIE_bp)										
  
  #define vInterruptOff()	USART3.CTRLA &= ~(1 << USART_DREIE_bp)
  
  xComPortHandle xSerialPortInitMinimal( unsigned long ulWantedBaud, unsigned portBASE_TYPE uxQueueLength )
  {
  	portENTER_CRITICAL();
  	{
  		/* Create the queues used by the com test task. */
  		xRxedChars = xQueueCreate( uxQueueLength, ( unsigned portBASE_TYPE ) sizeof( signed char ) );
  		xCharsForTx = xQueueCreate( uxQueueLength, ( unsigned portBASE_TYPE ) sizeof( signed char ) );
  
  
  		USART3.BAUD = (uint16_t)USART_BAUD_RATE(ulWantedBaud); /* set baud rate register */
  
  		USART3.CTRLA = 0 << USART_ABEIE_bp    /* Auto-baud Error Interrupt Enable: disabled */
  						| 0 << USART_DREIE_bp  /* Data Register Empty Interrupt Enable: disabled */
  						| 1 << USART_LBME_bp   /* Loop-back Mode Enable: enabled */
  						| USART_RS485_OFF_gc   /* RS485 Mode disabled */
  						| 1 << USART_RXCIE_bp  /* Receive Complete Interrupt Enable: enabled */
  						| 0 << USART_RXSIE_bp  /* Receiver Start Frame Interrupt Enable: disabled */
  						| 0 << USART_TXCIE_bp; /* Transmit Complete Interrupt Enable: disabled */
  
  		USART3.CTRLB = 0 << USART_MPCM_bp       /* Multi-processor Communication Mode: disabled */
  						| 0 << USART_ODME_bp     /* Open Drain Mode Enable: disabled */
  						| 1 << USART_RXEN_bp     /* Reciever enable: enabled */
  						| USART_RXMODE_NORMAL_gc /* Normal mode */
  						| 0 << USART_SFDEN_bp    /* Start Frame Detection Enable */
  						| 1 << USART_TXEN_bp;    /* Transmitter Enable: enabled */
  		
  	}
  	
  	portEXIT_CRITICAL();
  	
  	/* Unlike other ports, this serial code does not allow for more than one
  	com port.  We therefore don't return a pointer to a port structure and can
  	instead just return NULL. */
  	return NULL;
  }
  /*-----------------------------------------------------------*/
  
  signed portBASE_TYPE xSerialGetChar( xComPortHandle pxPort, signed char *pcRxedChar, TickType_t xBlockTime )
  {
  	/* 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;
  	}
  }
  /*-----------------------------------------------------------*/
  
  signed portBASE_TYPE xSerialPutChar( xComPortHandle pxPort, signed char cOutChar, TickType_t xBlockTime )
  {
  	/* Return false if after the block time there is no room on the Tx queue. */
  	if( xQueueSend( xCharsForTx, &cOutChar, xBlockTime ) != pdPASS )
  	{
  		return pdFAIL;
  	}
  	
  	vInterruptOn();
  	
  	return pdPASS;
  }
  /*-----------------------------------------------------------*/
  
  void vSerialClose( xComPortHandle xPort )
  {
  unsigned char ucByte;
  
  	/* Turn off the interrupts.  We may also want to delete the queues and/or
  	re-install the original ISR. */
  
  	portENTER_CRITICAL();
  	{
  		vInterruptOff();
  		
  		ucByte = USART3.CTRLB ;									
  		ucByte &= (0xFF ^(1 << USART_RXEN_bp));					
  		USART3.CTRLB = ucByte ;	
  		
  	}
  	portEXIT_CRITICAL();
  }
  /*-----------------------------------------------------------*/
  
  ISR(USART3_RXC_vect)
  {
  signed char ucChar, xHigherPriorityTaskWoken = pdFALSE;
  
  	/* Get the character and post it on the queue of Rxed characters.
  	If the post causes a task to wake force a context switch as the woken task
  	may have a higher priority than the task we have interrupted. */
  	ucChar = USART3.RXDATAL;
  
  	xQueueSendFromISR( xRxedChars, &ucChar, &xHigherPriorityTaskWoken );
  
  	if( xHigherPriorityTaskWoken != pdFALSE )
  	{
  		portYIELD_FROM_ISR();
  	}
  		
  }
  
  ISR(USART3_DRE_vect)
  {
  signed char cChar, cTaskWoken = pdFALSE;
  
  	if( xQueueReceiveFromISR( xCharsForTx, &cChar, &cTaskWoken ) == pdTRUE )
  	{
  		/* Send the next character queued for Tx. */
  		USART3.TXDATAL = cChar;
  	}
  	else
  	{
  		/* Queue empty, nothing to send. */
  		vInterruptOff();
  	}
  }
  