[PIC] pic16f877a uart not working

[navintiwari08]

hello there!
I'm trying to communicate with PC using pic16f877a's uart.. I've written a code in HITECH C.. but it doesn't seem to work.. pls help.. I'm using 20 MHz crystal and 9600 bauds..
the code is given below..

#include <htc.h>
#define _XTAL_FREQ 20000000
__CONFIG(FOSC_HS&LVP_OFF&CP_OFF&BOREN_OFF&PWRTE_OFF&WRT_OFF&WDTE_OFF);
unsigned char x;
void main()
{
    TRISC6 = 1;
    TRISC7 = 1;
    BRGH = 1;
    SYNC = 0;

    SPEN = 1;
    SPBRG = 129; //9600 baud with 20MHz
    TXIE = 1;
    RCIE = 1;
    GIE = 1;
    PEIE = 1;
       CREN = 1;
    TXEN = 1;
    while(1);
    
}

void interrupt ISR(void)
{
    if(RCIE && RCIF)
    {    
        x = RCREG;
        if(TXIF)
            TXREG = x;
            __delay_ms(100);
    }
}

 

[milan.rajik]

This might help you.

https://saeedsolutions.blogspot.in/2012/11/pic16f877-uart-code-proteus-simulation.html

 

[betwixt]

The code looks fine. Do you have an RS232 interface between the PIC and the PC port?

Brian.

 

[milan.rajik]

Remove delay instruction from ISR. RCIF needs to be cleared in ISR.

 

[betwixt]

On most PICs the RCIF is cleared by reading RCREG. Agreed - any delay in an ISR is bad news, it serves no useful purpose so take it out.

Brian.

 

[sana_akhtar]

I am not starting a new thread. My question is also related to this. here is my UART code

#ifndef _XTAL_FREQ
 #define _XTAL_FREQ 4000000
#endif


char UART_Init(const long int baudrate)
{
	unsigned int x;
	x = (_XTAL_FREQ - baudrate*64)/(baudrate*64);
	if(x>255)
	{
		x = (_XTAL_FREQ - baudrate*16)/(baudrate*16);
		BRGH = 1;
		SPBRG = x;
	 	SYNC = 0;
	    SPEN = 1;
        TRISC7 = 1;
        TRISC6 = 1;
        CREN = 1;
        TXEN = 1;
	    return 1;
	}
	if(x<256)
	{
	  BRGH=0;
	  SPBRG = x;
	  SYNC = 0;
	  SPEN = 1;
      TRISC7 = 1;
      TRISC6 = 1;
      CREN = 1;
      TXEN = 1;
	  return 1;
	}
	return 0;
}

char UART_TX_Empty()
{
  return TRMT;
}

char UART_Data_Ready()
{
   return RCIF;
}
char UART_Read()
{
 
  while(!RCIF);
  return RCREG;
}

void UART_Read_Text(char *Output, unsigned int length)
{
	int i;
	for(int i=0;i<length;i++)
		Output[i] = UART_Read();
}

void UART_Write(char data)
{
  while(!TRMT);
  TXREG = data;
}

void UART_Write_Text(char *text)
{
  int i;
  for(i=0;text[i]!='\0';i++)
	  TXREG=text[i];
}

I am just calling UART_Write_text function and passing a char string but it doesnt seems to work. Controller does send something but it is sending some random character. What is the possible error here.