Strange RS232 board behavior

[tonyyy]

Hi.
My board works fine with this code but then it doesn't. I am using Tera Term for sending
commands to the board. The board gets the command and executes it and send me back the
string. The problem is that after 3 or 4 attempts or after some time the board regonize
only the trasmitted command but any replies is received from it. Here
th code (pic is 16f876a):

#include <stdio.h>
#include <htc.h>
#include "usart.h"
#include <stdlib.h>


#ifndef _XTAL_FREQ
#define _XTAL_FREQ 10000000
#endif

__CONFIG(CP_OFF & BOREN_OFF & LVP_OFF & WDTE_OFF & PWRTE_ON & FOSC_HS );

void putch(unsigned char byte)
{
while(!TXIF)
continue;
TXREG = byte;
}


char getch() {/* retrieve one byte */
while(!RCIF) /* set when register is not empty */
continue;
return RCREG;
}

unsigned char
getche(void)
{
unsigned char c;
putch(c = getch());
return c;
}

void init_enable()
{

BRGH = 1; /* high baud rate */
SPEN = 1; /*attiva porta seriale */
SYNC = 0; /* asyncrono */
//passo 3
TXIE = 0; /* disable tx interrupts */
TX9 = 0; /* 8- or 9-bit transmission */
RX9 = 0; /* 8- or 9-bit reception */
TXEN = 1; /* enable the transmitter */
RCIE = 0; /* disable rx interrupts */
CREN = 1; /* enable reception */
SREN = 0; /* no effect */
}



void main(void){
PORTB = 0;
TRISB = 0;
TRISC = 0;
INTCON=0;
INIT_COMMS(); // set up the USART - settings defined in usart.h
init_enable();
char input;
while(1){
input = getch(); // read a response from the user
int i ;
for(i=0;i!=10; i++)
{
printf("test");
}

if (input == '1') {
RC0 = 1;
RC1 = 1;
RC2 = 1;
RC3 = 1;
RB3 = 1;
RB4 = 1;
RB5 = 1;
}


if (input == '2') {
RC3 = 1;
__delay_ms(1000);
RC3 = 0;
__delay_ms(2000);
RC3 = 1;
__delay_ms(1000);
RC3 = 0;
}
}

}



usart.h

#ifndef _SERIAL_H_
#define _SERIAL_H_

#define BAUD 9600
#define FOSC 10000000L
#define NINE 0 /* Use 9bit communication? FALSE=8bit */

#define DIVIDER ((int)(FOSC/(16UL * BAUD) -1))
#define HIGH_SPEED 1

#if NINE == 1
#define NINE_BITS 0x40
#else
#define NINE_BITS 0
#endif

#if HIGH_SPEED == 1
#define SPEED 0x4
#else
#define SPEED 0
#endif

#define RX_PIN TRISC7
#define TX_PIN TRISC6

/* Serial initialization */
#define INIT_COMMS()\
RX_PIN = 1;\
TX_PIN = 1;\
SPBRG = DIVIDER;\
RCSTA = (NINE_BITS|0x90);\
TXSTA = (SPEED|NINE_BITS|0x20)


void putch(unsigned char);
char getch(void);
unsigned char getche(void);

#endif

Thanks a lot.

 

[jayanth.devarayanadurga]

There is no code which sends or received strings. Is your commands 1 byte wide? Use Serial interrupt to receive data. Also make a function to send strings through UART.

 

[tonyyy]

There is no code which sends or received strings. Is your commands 1 byte wide? Use Serial interrupt to receive data. Also make a function to send strings through UART.

Hi. Thanks for your reply.
I see, so why istruction like

printf("test")

works for a while?

Yes, there is no string you are right. So the problem
should not occur using the putch below.

void putch(unsigned char byte)
{
while(!TXIF)
continue;
TXREG = byte;
}

Then I will use array :

while ((input=getch())!='\r') {
co = input;
putch(co); // echo to the terminal
i++;
}

// First command
if(strcmp(co, "com1") == 0)
{
RB2 = 1;
RB3 = 1;
RB4 = 1;
RB5 = 1;

_send_reply();

}


So assuming I want to reply to the command with a string the best is to create a function (i.e. _send_reply() )
which will take a string as parameter and uses TXREG for sending it char by char.


Thanks