gistfile1.c

// main.c

//  External HS XT Config bits
_FOSC( POSCMD_HS & OSCIOFNC_OFF );
_FOSCSEL( FNOSC_PRI & IESO_OFF );
_FWDT( FWDTEN_OFF );


int i = 0;

int main(int argc, char** argv) {

    OSCCONbits.COSC = 0b010;    //  HSXT no PLL
    OSCCONbits.CLKLOCK = 1;
    OSCCONbits.IOLOCK = 1;

    CLKDIVbits.ROI = 0;
    CLKDIVbits.DOZE = 0b000;
    CLKDIVbits.DOZEN = 1;

    setupUART();    //  In separate source file.  See below after "..."

    while(1);


    return (EXIT_SUCCESS);
}

void __attribute__(( __interrupt__, __auto_psv__ )) _U1TXInterrupt( void ){

    IFS0bits.U1TXIF = 0;        // Clear interrupt flag
    U1TXREG = 'b';
}


...

// Separate source file

#define FCY 8000000
#define BAUDRATE 9600
#define BRGVAL ((FCY/BAUDRATE)/16)-1

int setupUART(){

    //brgValue = ( FCY / ( 16 * baudRate )) - 1;

    U1MODEbits.UARTEN = 0;
    U1STAbits.UTXEN = 0;

    U1MODEbits.USIDL = 0;
    U1MODEbits.IREN = 0;
    U1MODEbits.RTSMD = 1;
    U1MODEbits.UEN = 0b00;
    U1MODEbits.WAKE = 0;
    U1MODEbits.LPBACK = 0;
    U1MODEbits.ABAUD = 0;
    U1MODEbits.URXINV = 0;
    U1MODEbits.BRGH = 0;            //  Enable low speed mode
    U1MODEbits.PDSEL = 0b00;
    U1MODEbits.STSEL = 0;

    U1STAbits.UTXISEL1 = 0;         
    U1STAbits.UTXISEL0 = 0;
    U1STAbits.UTXINV = 0;
    U1STAbits.UTXBRK = 0;
    

    U1BRG = BRGVAL;

    IFS0bits.U1TXIF = 0;            // Clear UART interrupt flag
    IEC0bits.U1TXIE = 1;            // Enable UART interrupts

    RPOR7bits.RP15R = 0b000011;     //  Set UART TX Pin to RP15

    U1MODEbits.UARTEN = 1;
    U1STAbits.UTXEN = 1;

    return 0;

}