RS232 communication in MPlab - serial-port

Question

I am using MPlab to read data from a pic micro controller. I am using pic18F87J11.
The data that I want to read is on pin 3 of the DB9 of the RS232, and my RS232 is connected to the pic micro controller.
Can anyone help me or give me a simple sample code to do that??
Thank you,

Answer 1

//
// Designed by www.MCUExamples.com
// rasika0612#gmail.com
// Serial communications example. Echo data comes to serial port
// using serial receive interrupt.
//
#include <p18f4520.h>
#pragma config OSC = HS // 20MHz Crystal, (HS oscillator)
#pragma config PBADEN = OFF // PORTB<4:0> pins are configured as digital I/O on Reset)
#pragma config WDT = OFF // watch dog timer off
#pragma config LVP = OFF // Low voltage program off
unsigned char cUART_char;
unsigned char cUART_data_flg;
void init_uart(void);
void UART_putc(unsigned char c);
void InterruptHandlerLow ();
void main()
{
init_uart(); // init UART module
while (1) // infinite loop which handles ncoming data as they arrive
{
if (cUART_data_flg==1)// if new data available, send it back through USART tx line (echo it)
{
UART_putc(cUART_char);
cUART_data_flg=0; // clear new data flag so one charactor will echoed once
}
}
}
//----------------------------------------------------------------------------
//----------------------------------------------------------------------------
#pragma code InterruptVectorLow = 0x18
void InterruptVectorLow (void)
{
_asm
goto InterruptHandlerLow //jump to interrupt routine
_endasm
}
//----------------------------------------------------------------------------
// Low priority interrupt routine
#pragma code
#pragma interrupt InterruptHandlerLow
void InterruptHandlerLow ()
{
if (PIR1bits.RCIF==1)//is interrupt occured by EUSART receive?,
//then RCREG is full we have new data (cleared when RCREG is read)
{
if(RCSTA&0x06) //more efficient way than following commented method to check for reception error
//if(RCSTAbits.FERR==1 || RCSTAbits.OERR==1 )
{
RCSTAbits.CREN=0; //Overrun error (can be cleared by clearing bit CREN)
cUART_char=RCREG; //clear Framing error
RCSTAbits.CREN=1;
}
else
{
cUART_char = RCREG; // read new data into variable
cUART_data_flg = 1; // new data received. so enable flg
}
}
}
//----------------------------------------------------------------------------
//----------------------------------------------------------------------------
void init_uart(void) // init UART module for 9600bps boud, start bit 1, stopbit 1, parity NONE
{
cUART_data_flg=0; // init data receive flag to zero (no data)
TRISCbits.TRISC7=1; //Make UART RX pin input
TRISCbits.TRISC6=0; //Make UART TX pin output
SPBRGH = 0x02; //9600bps 20MHz Osc
SPBRG = 0x08;
RCSTAbits.CREN=1; //1 = Enables receiver
RCSTAbits.SPEN=1; //1 = Serial port enabled (configures RX/DT and TX/CK pins as serial port pins)
BAUDCONbits.BRG16=1;//1 = 16-bit Baud Rate Generator – SPBRGH and SPBRG
TXSTAbits.SYNC=0; //0 = Asynchronous mode
TXSTAbits.BRGH=1; //1 = High speed
TXSTAbits.TXEN=1; //1 = Transmit enabled
RCONbits.IPEN = 1; //enable Interrupt priority levels
IPR1bits.RCIP=0; // EUSART Receive Interrupt Priority 0 = Low priority
PIE1bits.RCIE=1; // 1 = Enables the EUSART receive interrupt
INTCONbits.GIEL = 1;//enable interrupts
INTCONbits.GIEH = 1;
}
//----------------------------------------------------------------------------
//----------------------------------------------------------------------------
void UART_putc(unsigned char c)
{
TXSTAbits.TXEN=0;// disable transmission
TXREG=c; // load txreg with data
TXSTAbits.TXEN=1; // enable transmission
while(TXSTAbits.TRMT==0) // wait here till transmit complete
{
Nop();
}
}