ABOUT START END CHARACTERS ON RS232

[Sebastian]

HI ALL

I HAVE WRITE THIS CODE BUT I HAVE A PROBLEM

#if defined(__PCH__)
#include <18F452.h>
#fuses HS,NOWDT,NOPROTECT,NOLVP
#use delay(clock=20000000)
#use rs232(baud=2400, xmit=PIN_C6, rcv=PIN_C7)
#endif

#include <input.c>

void main() {

int value;
char string;

// int value1=0b00000000; // DEC 0
int value2=0b00000001; // DEC 1

set_tris_B(0x00);
set_tris_D(0xFF);

while (TRUE){

output_b(0x00);
value=input_d();


if (value==value2){

printf("?0001wdloa;1; ?");

delay_ms(500);

gets(string);
{
if ( strcmp(string,?00011;AD?))
output_b(0x0F);
}
}
}
}


IN THIS LINE
printf("?0001wdloa;1; ?");
MPLAB NOT PERMIT TO INSERT THE CHARACTER ASCII HEX 02
SYM STX THE SAME WITH CHARACTER 03HEX SYM ETX
AFTER SAVE FILE EXIT PROJECT AND REOPEN MPLAB REPLACE
THE CARACTERS WITH ?

THERE IS ONE WAY TO PREVENT THIS ??
CAN I TRANSMIT CHARACTERS ON RS 232 IN 8 BIT FORMAT ?

THANK YOU ....

[Ttelmah]

This is not MPLAB, but standard C.
An ASCII control character, has to be declared using an 'escape sequence'. These are:
\0 = ASCII '0'
\nnn = ASCII 'nnn', in octal
\xhh = ASCII 'hh' in hex
\a = 'alert' (bell) character
\b = 'backspace'
\f = 'formfeed'
\n = 'newline'
\r = 'carriage return'
\t = 'horizontal tab'
\v = 'vertical tab'
\\ = the 'backslash' character itself
\? = Question mark
\' = the 'single quote' character
\" = the 'double quote' character

So for the STX character you need (start of transmission), you need to use either \x02 or \002 i the string declaration, and for ETX, \x3 or \003.
Remember that C is designed so that you might well be typing it in using a terminal, and you obviously cannot type a STX, or ETX code into a string, since it would start/stop the actual transmission...

Best Wishes

[Sebastian]