RS232-PIC is locking up

[Joris H]

Hi,
In my project I use a PIC16f877-20/P. I try to communicate with a GSM-module. When I run the code then the LCD display: -AT+CMGR= xxx
(this is code that I send) after that the PIC is locking up. The displayed time is stopped.
I tryed to put the " printf(lcd_putc,"\%S",receved_from_modem);"line directly in the "get_string(receved_from_modem,int max)" and then I got the complete responce from the module in one long string. I tryed other AT-Commands with the same result.

Why is the PIC locking up?

Please HELP

CCS: 3.091

some code:

#include <16F877.h>
#use delay(clock=20000000)
#fuses HS,NOWDT,NOBROWNOUT,NOLVP,NOPROTECT
#use fixed_io(c_outputs=pin_C6)
#use rs232(baud=9600,parity=n,bits=8,xmit=PIN_C6,rcv=PIN_C7)

#int_RDA
RDA_isr() {
get_string(receved_from_modem,160);
bit_set(ModemFlag,RecMess);
}

void main() {
int b;

rtc_init();
lcd_init();
init_ext_eeprom();
enable_interrupts(INT_RDA);
enable_interrupts(global);

strcpy(OK, "OK");
do
{Display_MainMenu();}
while(TRUE);
}

void get_string(receved_from_modem,int max) {
int len;
char c;
max--;
len=0;
do {
c=getc();
if(c==0x0A ||c==0x0D) { //DEL first CR and LF
if(len<2) {
len--;
c='z';

}
} else if ((c>=' ')&&(c<='~'))
if(len<max) {
len=len+1;
receved_from_modem[len]=c;


}
} while(c!=0x0A ); //(c!=LF)||(c!=CR)||
receved_from_modem[len]=0;
//printf(lcd_putc,"\fyy%S",receved_from_modem);
}


run_manual()
{lcd_putc("\fGSM ");
disable_interrupts(global);
printf("AT+CMGR=1\n");
delay_us( 1000 );
enable_interrupts(INT_RDA);
enable_interrupts(global);
do {
Display_Time(); //display the real time hh:mm:ss

if (bit_test(ModemFlag,RecMess))
{bit_clear(ModemFlag,RecMess);

printf(lcd_putc,"\%S",receved_from_modem);
printf(lcd_putc," xxx ");}
}
while (TRUE);

[Neutone]

You are not handeling errors in your USART. If you recieve more than a single byte while performing a task like formatting a string the recieve buffer will over run.

[Humberto]

Joris
Try this way, don't tested but it will work. Just to show how I will do it.
Let us know if this aproach is usefull for you.

Best wishes,

Humberto

[Joris H]

Thanks for the help
I reworked a bit the sample code send by Humberto
For your info here the code for the interrupt

RDA_isr() {
int len;

char c;

do{

c=getc();

if(c==LF ) //DEL first CR and LF from the mess.
{if (len<=2)

Thanks again

Joris
{len=0;

c=0;
}}
else if (c>=' '&& c<='~')
{

receved_from_modem[len]=c;
len++;
len_mess=len; //find the # of caracters
}
if(c==LF ); //(c!=LF)||(c!=CR)|| //End of mess.
{
bit_set(ModemFlag,RecMess);
receved_from_modem[len]=0;
disable_interrupts(INT_RDA); //get out of interrupt
}
if (len>=BUFFER_SIZE) //someting went wrong
{

bit_set(ModemFlag,RecErr);
disable_interrupts(INT_RDA); //get out
}}
while (c!=LF );

len=0;
}

[densimitre]

Hi

If I have a 16F877 in asincronous and full duplex mode, when I send a "AT <CR>" to modem, what happend?

1.- The modem answer after "A" with a "A" but PIC don�t listen up to finish send all "AT <CR>" comand???
2.- The PIC read that "A" and after send the "T" and so on?..

How can i prevent lost data?

Thank you very much