/*
** OBD.c
** OBD interface from Suzuki SDL to PC comm port
** Version 1
** J Holland
** 19th April 2008
**
** SDL is single wire bi-directional interface
** implemented by resistors
**
** U1 is OBD is 15625bps???
** U2 is COMM port is 115200bps
** U1_TX is implemented as open drain output
** RB5 is initialised as output (low)
** when U1_TX goes high SDL is connected and UART is initialised
** and LED6 (RA3) is switched off
** LED7 (RA4) indicates data reception error on U1
** Comparator is used to clean up RX signal.
*/

#include <p24fj128ga010.h>


 
#define RXFLG_SET_MSK	0x0001
#define	RXFLG_CLR_MSK	0xFFFE
#define	RB14_DIG_MSK	0x4000

#define TRUE = 1;
#define FALSE = 0;


// timing and baud rate calculations (Fcy = 16MHz) -- note Fcy = Fosc/2
#define U1_BRATE   	66        	// 15126 baud (BREGH=0)
#define U2_BRATE	34			// 115200 baud (BREGH=1)



int U1_STATUS;
int U2_STATUS;




void obd_init()
{
	//set up ports
	
	PORTA &= 0xFFFE;			//turn off LED7
	TRISA = 0xFFF3;				//RA7,RA6 are LEDs
	
	PORTB = 0xFFDF;				//RB5 inits low
	TRISB = 0xFFDF;				//RB5 = output
	AD1PCFG = 0xFFFF;			//PORTB all digital
	
	TRISC = 0xFFFF;
	TRISD = 0xFFFF;
	TRISE = 0xFFFF;

	// initialize the UART1 serial port

	PORTFbits.RF3=0;			//set U1_TX low
	ODCF = 0x0008;				//U1_Tx = open drain 
	TRISF = 0xFFFF;				//PORTF all inputs

									
	//clear (my) status registers
	U1_STATUS = 0x0000;	//clear all status flags
	U2_STATUS = 0x0000;
	
	
	
}


void initComp1 (void)
{
	TRISB = 0xFEFF;				//init RB8=C1_OUT,RB5=C1_IN
	AD1PCFGbits.PCFG5=0;		//RB5 is analogue in
	CMCON = 0x0512;			//internal vref, input to -ve, inv output, enabled
	CVRCON = 0x00C6;		//Vref = 1.44V, Vref on RB10
	CMCONbits.C1EVT=0;
}	





void initU1( void)			//OBD interface
{


	//set up interrupts for U1
	IPC3bits.U1TXIP1 = 0;
	IPC3bits.U1TXIP0 = 0;
	IPC2bits.U1RXIP2 = 1; 			//Set Uart RX Interrupt Priority
	IPC2bits.U1RXIP1 = 0;
	IPC2bits.U1RXIP0 = 0;
	
	U1BRG = U1_BRATE;    			//set up baud rate
	U1MODEbits.BRGH = 0; 			//Use low speed mode - see errata!!!
	U1MODEbits.UARTEN = 1;			//enable UART
//	U1STAbits.UTXINV = 1;			//invert TX line 
	U1STAbits.UTXEN = 1; 			//Enable Transmit
	IFS0bits.U1RXIF = 0;			//clear interrupt flag before enabling
	IEC0bits.U1RXIE = 1; 			//Enable Receive Interrupt
	TRISFbits.TRISF3=0;
	
} // initU1



void initU2( void)		//PC Interface
{
	// initialize the UART2 serial port
	

	IPC7bits.U2TXIP1 = 0;
	IPC7bits.U2TXIP0 = 0;
	IPC7bits.U2RXIP2 = 1; 		//Set Uart RX Interrupt Priority
	IPC7bits.U2RXIP1 = 0;
	IPC7bits.U2RXIP0 = 0;

	U2BRG = U2_BRATE;    
	U2MODEbits.BRGH = 1; 
	U2MODEbits.UARTEN = 1;
	U2STAbits.UTXEN = 1; 		//Enable Transmit
	IFS1bits.U2RXIF = 0;		//clear interrupt flag before enabling
	IEC1bits.U2RXIE = 1; 		//Enable Receive Interrupt
	TRISFbits.TRISF5 = 0;
} // initU2






// send a character to the UART1 serial port
void putC_U1( int c)
{
	while ( U1STAbits.UTXBF);   // wait if Tx buffer full
	U1TXREG = c;
} // putU1


// get a new character the UART1 serial port
int getC_U1( void)
{
 	return U1RXREG;		// read the character from the receive buffer

}// getU1



// send a character to the UART2 serial port
void putC_U2( int c)
{
	while ( U2STAbits.UTXBF);   // wait if Tx buffer full
	U2TXREG = c;
} // putU2


// wait for a new character to arrive to the UART2 serial port
int getC_U2( void)
{
    return U2RXREG;		// read the character from the receive buffer
}// getU2







main()
{
		obd_init();						//call initialisation code
		
		
		while((PORTFbits.RF3==0))			//wait till RF3 goes high	
		{
			PORTAbits.RA3 = 1;			//set 'not ready LED'
			}
			
		//   ******************** add debounce delay
		
		initComp1();					//initialise comparator
		initU1();						//initialise UART1
		initU2();						//initialise UART2
		PORTAbits.RA3 = 0;				//clear 'not ready LED'
		
	
	int c1;
	int c2;
	
	while (1)
	{		
		if((U1_STATUS & RXFLG_SET_MSK) == 1){
			c1 = getC_U1();
			if((U1STAbits.FERR==1) | (U1STAbits.OERR ==1))
					PORTA |= 0x08;								//RA4 ON = error
			U1_STATUS = (U1_STATUS & RXFLG_CLR_MSK);			//ONLY IF RX BUFFER EMPTY?????
			putC_U2(c1);
		}

		if((U2_STATUS & RXFLG_SET_MSK) == 1){
			
			c2 = getC_U2();
			U2_STATUS = (U2_STATUS & RXFLG_CLR_MSK);
			putC_U1(c2);
			}
	}

}// main



/******************************  Interrupt Service Routines  ************************/

/* Fast context save (using push.s and pop.s)  ?????     */



void __attribute__ ((interrupt, no_auto_psv)) _U1RXInterrupt(void)
	 {
	
		U1_STATUS = (U1_STATUS | RXFLG_SET_MSK);	// set (polled) U1 status register rx flag  
		IFS0bits.U1RXIF = 0;						//clear interrupt flag before returning
	
	}


void __attribute__ ((interrupt, no_auto_psv)) _U2RXInterrupt(void)
	 {

		U2_STATUS = (U2_STATUS | RXFLG_SET_MSK);				// set (polled) U2 status register rx flag  
		IFS1bits.U2RXIF = 0;									// clear interrupt flag before returning
	
	}



/********* END OF INTERRUPT SERVICE ROUTINES ********/