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/*
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    Copyright (C) 2004    John Orlando
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   AVRcam: a small real-time image processing engine.
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    This program is free software; you can redistribute it and/or
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    modify it under the terms of the GNU General Public
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    License as published by the Free Software Foundation; either
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    version 2 of the License, or (at your option) any later version.
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    This program is distributed in the hope that it will be useful,
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    but WITHOUT ANY WARRANTY; without even the implied warranty of
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    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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    General Public License for more details.
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    You should have received a copy of the GNU General Public
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    License along with this program; if not, write to the Free Software
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    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
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   For more information on the AVRcam, please contact:
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   john@jrobot.net
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   or go to www.jrobot.net for more details regarding the system.
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*/
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/***********************************************************
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	Module Name: UartInterface.c
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	Module Date: 04/10/2004
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	Module Auth: John Orlando
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	Description: This module is responsible for providing an
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	interface to the UART hardware available on the mega8.
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	This interface is an interrupt-driven interface.
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    Revision History:
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    Date        Rel Ver.    Notes
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    4/10/2004      0.1     Module created
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    6/30/2004      1.0     Initial release for Circuit Cellar
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                           contest.
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    11/15/2004     1.2     Updated UART baud rate regs so that
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                           it runs at 115.2 kbps when the input
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                           crystal is at 17.7 MHz (which is the
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                           speed of the OV6620's crystal).
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    1/16/2005      1.4     Moved the serial received ISR to
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                           this file, instead of having it
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                           in its own UartInterfaceAsm.S file
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                           written in assembly.
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***********************************************************/
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/*	Includes */
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#include <avr/io.h>
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#include <avr/interrupt.h>
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#include "CommonDefs.h"
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#include "UartInterface.h" 
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#include "UIMgr.h"
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#include "Executive.h"
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/*  Local Variables */
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/* 	Local Structures and Typedefs */
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/*  Extern Variables */
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/*  Definitions */
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/***********************************************************
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	Function Name: UartInt_init
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	Function Description: This function is responsible for
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	initializing the UART interface on the mega8.  This 
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	interface is set to communicate at 115.2 Kbps, with an
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	8N1 protocol.
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	Inputs:  none
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	Outputs: none
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***********************************************************/	
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void UartInt_init(void)
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{	
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	/* set up the baud rate registers so the UART will operate
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	at 115.2 Kbps */
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	UBRRH = 0x00;
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#ifdef NO_CRYSTAL    
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    UBRRL = 18;  /* 18 for double clocking at 115.2 kbps */
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#else    
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	UBRRL = 0x08;  /* for 16 MHz crystal at 115.2 kbps */
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#endif    
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	/* enable the tx and rx capabilities of the UART...as well 
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		as the receive complete interrupt */
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	UCSRB = (1<<RXCIE)|(1<<RXEN)|(1<<TXEN);	
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	/* set up the control registers so the UART works at 8N1 */
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	UCSRC = (1<<URSEL)|(1<<UCSZ1)|(1<<UCSZ0);
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#ifdef NO_CRYSTAL     
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    /* set the baud rate to use the double-speed */
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    UCSRA = (1<<U2X);
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#endif    
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}
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/***********************************************************
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	Function Name: UartInt_txByte
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	Function Description: This function is responsible for
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	transmitting a single byte on the uart.  
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	Inputs:  txByte - the byte to send
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	Outputs: none
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	NOTES: When the TX UDRE (data register empty) is set, there
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	is puposefully no interrupt...thus, to send a string of
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	data out, the calling routine needs to hold up the entire
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	application while this takes place (or just send one
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	byte at a time at strtegically timed intervals, like
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	the stats data is sent out :-)
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***********************************************************/
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void UartInt_txByte(unsigned char txByte)
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{
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	/* Wait for empty transmit buffer */
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	while ( !( UCSRA & (1<<UDRE)) );
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	/* Put data into buffer, sends the data */
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	UDR = txByte;
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}
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/***********************************************************
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	Function Name: SIG_UART_RECV ISR
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	Function Description: This function is responsible for
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	handling the interrupt caused when a data byte is 
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    received by the UART.
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	Inputs:  none
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	Outputs: none
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	NOTES: This function was originally written in assembly,
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    but moved over to C when the setting of the "T" bit at
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    the end of the routine was no longer necessary (this
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    theoretically allowed the AVRcam to respond to serial
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    bytes in the middle of tracking or dumping a frame.
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    But it wasn't really needed, and understanding the C
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    is easier  :-)
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***********************************************************/
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SIGNAL(SIG_UART_RECV)
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{
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    unsigned char tmpHead;
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    /* read the data byte, put it in the serial queue, and
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    post the event */
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    UIMgr_rxFifo[UIMgr_rxFifoHead] = UDR;
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    /* now move the head up */
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    tmpHead = (UIMgr_rxFifoHead + 1) & (UI_MGR_RX_FIFO_MASK);
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    UIMgr_rxFifoHead = tmpHead;
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    /* write the serial received event to the event fifo */
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    Exec_eventFifo[Exec_eventFifoHead] = EV_SERIAL_DATA_RECEIVED;
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    /* now move the head up */
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    tmpHead = (Exec_eventFifoHead + 1) & (EXEC_EVENT_FIFO_MASK);
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    Exec_eventFifoHead = tmpHead;
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}
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