Demo/PIC18_WizC/serial/serial.c

/*
    FreeRTOS V6.0.1 - Copyright (C) 2009 Real Time Engineers Ltd.

    ***************************************************************************
    *                                                                         *
    * If you are:                                                             *
    *                                                                         *
    *    + New to FreeRTOS,                                                   *
    *    + Wanting to learn FreeRTOS or multitasking in general quickly       *
    *    + Looking for basic training,                                        *
    *    + Wanting to improve your FreeRTOS skills and productivity           *
    *                                                                         *
    * then take a look at the FreeRTOS eBook                                  *
    *                                                                         *
    *        "Using the FreeRTOS Real Time Kernel - a Practical Guide"        *
    *                  http://www.FreeRTOS.org/Documentation                  *
    *                                                                         *
    * A pdf reference manual is also available.  Both are usually delivered   *
    * to your inbox within 20 minutes to two hours when purchased between 8am *
    * and 8pm GMT (although please allow up to 24 hours in case of            *
    * exceptional circumstances).  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 exception 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!

    http://www.FreeRTOS.org - Documentation, latest information, license and
    contact details.

    http://www.SafeRTOS.com - A version that is certified for use in safety
    critical systems.

    http://www.OpenRTOS.com - Commercial support, development, porting,
    licensing and training services.
*/

/*
Changes from V3.0.0
	+ ISRcode removed. Is now pulled inline to reduce stack-usage.

Changes from V3.0.1
*/

/* BASIC INTERRUPT DRIVEN SERIAL PORT DRIVER. */

/* Scheduler header files. */
#include "FreeRTOS.h"
#include "task.h"
#include "queue.h"

#include "serial.h"

/* Hardware pin definitions. */
#define serTX_PIN				bTRC6
#define serRX_PIN				bTRC7

/* Bit/register definitions. */
#define serINPUT				( 1 )
#define serOUTPUT				( 0 )
#define serINTERRUPT_ENABLED 	( 1 )

/* All ISR's use the PIC18 low priority interrupt. */
#define	serLOW_PRIORITY			( 0 )

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

/* Queues to interface between comms API and interrupt routines. */
xQueueHandle xRxedChars; 
xQueueHandle xCharsForTx;
portBASE_TYPE xHigherPriorityTaskWoken;

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

xComPortHandle xSerialPortInitMinimal( unsigned long ulWantedBaud, unsigned char ucQueueLength )
{
	unsigned short usSPBRG;
	
	/* Create the queues used by the ISR's to interface to tasks. */
	xRxedChars = xQueueCreate( ucQueueLength, ( unsigned portBASE_TYPE ) sizeof( char ) );
	xCharsForTx = xQueueCreate( ucQueueLength, ( unsigned portBASE_TYPE ) sizeof( char ) );

	portENTER_CRITICAL();

	/* Setup the IO pins to enable the USART IO. */
	serTX_PIN	= serINPUT;		// YES really! See datasheet
	serRX_PIN	= serINPUT;

	/* Set the TX config register. */
	TXSTA = 0b00100000;
		//	  ||||||||--bit0: TX9D	= n/a
		//	  |||||||---bit1: TRMT	= ReadOnly
		//	  ||||||----bit2: BRGH	= High speed
		//	  |||||-----bit3: SENDB = n/a
		//	  ||||------bit4: SYNC	= Asynchronous mode
		//	  |||-------bit5: TXEN	= Transmit enable
		//	  ||--------bit6: TX9	= 8-bit transmission
		//	  |---------bit7: CSRC	= n/a

	/* Set the Receive config register. */
	RCSTA = 0b10010000;
		//	  ||||||||--bit0: RX9D	= ReadOnly
		//	  |||||||---bit1: OERR	= ReadOnly
		//	  ||||||----bit2: FERR	= ReadOnly
		//	  |||||-----bit3: ADDEN	= n/a
		//	  ||||------bit4: CREN	= Enable receiver
		//	  |||-------bit5: SREN	= n/a
		//	  ||--------bit6: RX9	= 8-bit reception
		//	  |---------bit7: SPEN	= Serial port enabled

	/* Calculate the baud rate generator value.
	   We use low-speed (BRGH=0), the formula is
	   SPBRG = ( ( FOSC / Desired Baud Rate ) / 64 ) - 1 */
	usSPBRG = ( ( APROCFREQ / ulWantedBaud ) / 64 ) - 1;
	if( usSPBRG > 255 )
	{
		SPBRG = 255;
	}
	else
	{
		SPBRG = usSPBRG;
	}

	/* Set the serial interrupts to use the same priority as the tick. */
	bTXIP = serLOW_PRIORITY;
	bRCIP = serLOW_PRIORITY;

	/* Enable the Rx interrupt now, the Tx interrupt will get enabled when
	we have data to send. */
	bRCIE = serINTERRUPT_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;
}
/*-----------------------------------------------------------*/

xComPortHandle xSerialPortInit( eCOMPort ePort, eBaud eWantedBaud, eParity eWantedParity, eDataBits eWantedDataBits, eStopBits eWantedStopBits, unsigned char ucBufferLength )
{
	/* This is not implemented in this port.
	Use xSerialPortInitMinimal() instead. */
	return NULL;
}
/*-----------------------------------------------------------*/

portBASE_TYPE xSerialGetChar( xComPortHandle pxPort, char *pcRxedChar, portTickType 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 ( char ) pdTRUE;
	}

	return ( char ) pdFALSE;
}
/*-----------------------------------------------------------*/

portBASE_TYPE xSerialPutChar( xComPortHandle pxPort, char cOutChar, portTickType xBlockTime )
{
	/* Return false if after the block time there is no room on the Tx queue. */
	if( xQueueSend( xCharsForTx, ( const void * ) &cOutChar, xBlockTime ) != ( char ) pdPASS )
	{
		return pdFAIL;
	}

	/* Turn interrupt on - ensure the compiler only generates a single 
	instruction for this. */
	bTXIE = serINTERRUPT_ENABLED;

	return pdPASS;
}
/*-----------------------------------------------------------*/

void vSerialClose( xComPortHandle xPort )
{
	/* Not implemented for this port.
	To implement, turn off the interrupts and delete the memory
	allocated to the queues. */
}