Problem with GSM switch and 89c51

Especially considering that the maximum length of an SMS is - what?

In processors with limited memory, you normally don't have large buffers for storing worst-case multiline data. The normal way to handle things is to have a state machine that processers received characters on-the-fly (either directly from the serial port but often using a smaller ring-buffer to reduce the tight time coupling between serial port and processing).

The state machine can then figure out what is the start of a new text line, what is echo, what is answer, etc. And when processing answers, it can on-the-fly decode the individual fields in the answer to extract time, message etc. And such state machines can also take care of any unexpected unsolicited messages you may receive from a modem, such as a ring message if someone happens to ring the subscriber number while you think you are about to check for reception of an SMS - the modem promises that any unsolicited messages will not be inlined inside other text l ines so it's trivial for a state machine to handle them while handling all other answers.

So you can constantly check if your state machine have found something interesting you want to handle - like an unsolicited message that the modem has an overtemperature or other interesting messages it may be capable to report. And you can send commands to the modem and within a timeout interval check that you get expected responses - any enabled echo strings, ok/error strings, any specific answer string. When you have received what you should recieve or an error message, you can then figure out what to do next, i.e. if you have more strings to send to the modem.

First of all i want to thank you for you time. I have an Philips 89C51RD+.
The delay_sms() creates a delay in ms, e.x. delay_sms(1000) creates 1sec delay.
I'll try to fix the things you recommended but i really don't understand state machines.
I'll sent you the new code when i done it.

The delay_sms() creates a delay in ms, e.x. delay_sms(1000) creates 1sec delay.
maybe today, maybe tomorrow, maybe not next week

NOBODY knows what a compiler will do to a delay routine, delays MUST be done in assemble or with timers

Also, why is there no indentions in your code, it is very tough to read

Erik

I fix some of the errors you indicated me but still the code is not running properly.
I can receive whatever i sent with the SMSString() but i can't receive the sms to the microcontroller and of course i can't get the phone number and the message from it.
This is my fixed code

#include <reg51.h>
#include <string.h>

sbit Water=P2^0;
sbit Window=P2^1;

//declarations

void clear(void);
void tx0(unsigned char);
void delay_sms (unsigned int);
void SMSString(char*text) ;
void init();
void Status();
void init_modem();
void process_modem_character(unsigned char *);

unsigned char idata phone[15];               // Store received phone number
unsigned char idata msg1[100];               // Store received message
unsigned char j,abc;
//unsigned char idata tmp10[27];

void serial () interrupt 4 using 1
{
if(RI)            //receive mode
{
RI=0;
abc=SBUF;
if(abc<100)
{
msg1[abc++]=SBUF;
}
else
{
RI=1;
}
}
}

void main (void)
{
clear();
init();
init_modem();

do
{
IE=0X90;   // Enable serial interrupt
delay_sms(1000);

// i get a response like this
// +CMGR: "REC UNREAD","+3069********",,"11/04/09,11:26:48+12"
// Window on
// OK
// I think that's the format the 8051 get
// \+CMTI\: \"SM\",1\r+CMGR: \"REC UNREAD\"\,\"+306982037789\"\,\,\"11\/04\/09\,11\:26\:48\+12\"\rStatus\n\rOK\r

process_modem_character(msg1);    // read sms and store it

if(strncmp("Water on",msg1,8)==0)
{
Water=1;
Status();
}
else  if(strncmp("Water off",msg1,9)==0)
{
Water=0;
Status();
}
else  if(strncmp("Window on",msg1,9)==0)
{
Window=1;
Status();
}
else  if(strncmp("Window off",msg1,10)==0)
{
Window=0;
Status();
}
else  if(strncmp("Status",msg1,6)==0)
{
Status();
}
else
{
SMSString("AT+CMGS=\"");
SMSString(phone);
SMSString("\"+<CR>\r");
delay_sms(1000);
SMSString("Wrong Command");
SMSString("\n\r");
delay_sms(1000);

SMSString(phone);
delay_sms(1000);

SMSString(msg1);
delay_sms(1000);
}
SMSString("AT+CMGD=1\r");
delay_sms(1000);

IE=0X00;   // Disable serial interrupt
delay_sms(1000);

}
while(1);
}

void init(void)
{
j=0;
abc=0;
TL1=0XFD; //9600 @ 11.0592
TH1=0xFD;
TMOD=0x20;
SCON=0x50;
TR1=1;
}

void SMSString(unsigned char* text) //function to send SMS using GSM modem
{
while (*text)
{
tx0(*text++);
}
}


void tx0(unsigned char x) //send data to serial port 0
{
EA=0;
SBUF=x;
while(TI==0);
TI=0;
EA=1;
}


void delay_sms (unsigned int count)
{
unsigned int i;
    while(count) {
        i = 115;
                while(i>0) i--;
        count--;
}
}

void init_modem(void)
{
Window=0;
Water=0;


SMSString("AT\r"); // AT commands to initialize gsm modem
delay_sms(1000);

SMSString( "ATe0\r"); // turn off echo
delay_sms(1000);

SMSString( "AT&W\r"); // save settings
delay_sms(1000);

SMSString( "AT+CMGF=1\r"); // select text mode for sms
delay_sms(1000);

SMSString( "AT+CNMI=2,1,0,0,0\r"); // notification of new sms
delay_sms(1000);

SMSString( "AT+CMGR=1\r"); // AT command to read sms
delay_sms(1000);
}

void Status(void)
{
//tmp10 = sprintf( SBUF, "Water is %s and Window is %s\n" , Water, Window);
SMSString("AT+CMGS=\"");
SMSString(phone);
SMSString("\"+<CR>");
delay_sms(1000);
//SMSString(tmp10);
SMSString("\n\r");
delay_sms(1000);
}

enum States {
    STATE_IDLE,
    STATE_FIND_CMT,
    STATE_CMT_GET_NUMBER,
    STATE_CMT_GET_COMMA,
    STATE_CMT_GET_MSG_START,
    STATE_CMT_GET_MSG,
} state = STATE_IDLE;
const char* pattern;
int ch;

void process_modem_character(unsigned char*msg) {
    switch (state) {
        case STATE_IDLE:
            if (msg == '+') {
                state = STATE_FIND_CMT;
                pattern = "\+CMTI\: \"SM\",1\r+CMGR: \"REC UNREAD\"\,\"";
            }
            break;
        case STATE_FIND_CMT:
            if (*pattern != msg) {
                state = STATE_IDLE;
            } else {
                pattern++;
                if (*pattern == '\0') {
                    state = STATE_CMT_GET_NUMBER;
                    ch = 0;
                }
            }
            break;
        case STATE_CMT_GET_NUMBER:
            if (msg == '\"') {
                state = STATE_CMT_GET_COMMA;
            } else if (ch >= sizeof(phone)) {
                // Too long phone number :(
                state = STATE_IDLE;
            } else {
                                ch++;
                phone[ch] = *msg;
                phone[ch] = '\0';
            }
            break;
        case STATE_CMT_GET_COMMA:
            if (msg == ' ') {
                ;    // Ignore white space
            } else if (msg == ',') {
                state = STATE_CMT_GET_MSG_START;
            } else {
                // Invalid character received
                state = STATE_IDLE;
            }
            break;

        default:
            // Invalid state.
            state = STATE_IDLE;
    } // switch
} // process_modem_character
void clear(void)
{
unsigned char a;
for(a=0;a<100;a++)
msg1[a]=0x00;
}

Please help

This is not how to receive data:

void serial () interrupt 4 using 1 {
    if (RI) {            //receive mode
        RI=0;
        abc=SBUF;
        if(abc<100) {
            msg1[abc++]=SBUF;
        } else {
            RI=1;
        }
    }
}

Seems more like random changes.

Look at standard example code for receiving serial data in interrupt handler.
But abc (which you haven't still renamed to something meaningful) should not be assigned from SBUF - for every character received on the UART you may only read one (1) time from SBUF.

And you call process_modem_character(msg1) without caring if msg1 contains any characters.
And your state machine doesn't consume any characters.
And you have code like:

if (*pattern != msg) ...

but pattern is a pointer to char and msg is a pointer to unsigned char. Besides mixing char and unsigned char - what does the star do? *pattern would be the character pointed to by pattern. But msg is not a character but a pointer - comparing a character and a pointer isn't meaningful.

Try to implement a ring buffer or incomming data, and have your processing check if the ring buffer have data available. Then eat data and switch states depending on what you find. And keep track of pauses where you have no data or line endings to synchronize your state machine.

You don't get anything to work for the simple reason that you have neither tried to debug this code by running it and comparing what happens with what you expected, nor have you tried to just in your head evaluate these lines and figure out what values the different variables might have and what would happen if you step the code in your head. The major part of writing code is actually stepping the code in the head - we can't run a debugger until we have code, but we must be able to read and understand without debugger to be able to write the code in the first place.

void serial () interrupt 4 using 1
    {
    if (RI)
        {            //receive mode
        RI=0;
        abc=SBUF;
        if(abc<100)
        {
            msg1[abc++]=SBUF;
        }
        else
        {
            RI=1; /////////// this will get you right back into the ISR
        }
    }
}

I had to reformat your code to verufy this, what is wrong with lining the braces up???, look at the comment above.

Erik

        abc=SBUF;
....
            msg1[abc++]=SBUF;

storing in a buffer indexed by the hex value of the character received?????

It looks to me as if you do not believe in the adage "think before you do"

Erik

Brace positioning is very much a matter of strongly-held personal preference.

Many people like their braces on the end of the "controlling" line:

   if( test ) {
      // stuff
   } else {
      // alternative stuff
   }

Some people (like me) like their braces alone on a line, aligned with the "controlling" line

   if( test )
   {
      // stuff
   }
   else
   {
      // alternative stuff
   }

Some people (quite inexplicably, IMO) like their braces alone on a line, aligned with the "controlled" line(s)

   if( test )
      {
      // stuff
      }
   else
      {
      // alternative stuff
      }

To name but three.

The important thing is, whatever you choose, to be consistent

I modified my braces and changed the serial interrupt but there is still a lot work to be done.

#include <reg51.h>
#include <string.h>
#include <stdio.h>

sbit Water=P2^0;
sbit Window=P2^1;

//declarations
void clear(void);
void tx0(unsigned char);
void delay_sms (unsigned int);
void SMSString(char*text) ;
void init();
void Status();
void init_modem();
void process_modem_character(unsigned char *);

unsigned char idata phone[15];               // Store received phone number
unsigned char idata msg1[100];               // Store received message
unsigned char j,bufcounter;

void serial () interrupt 4 using 1
{
    if (RI)
        {
        while(!RI)
                {
                RI=0;
                if(bufcounter<100)
                {
                msg1[bufcounter++]=SBUF;
                }
                }
    }
}
void main (void)
{
        clear();
        init();
        init_modem();
        do
                {
                        IE=0X90;   // Enable serial interrupt
                        delay_sms(1000);

                // i get a response like this
                // +CMGR: "REC UNREAD","+3069********",,"11/04/09,11:26:48+12"
                // Window on
                // OK
                // I think that's the format the 8051 get
                // \+CMTI\: \"SM\",1\r+CMGR: \"REC UNREAD\"\,\"+3069********\"\,\,\"11\/04\/09\,11\:26\:48\+12\"\rStatus\n\rOK\r

                        process_modem_character(msg1);    // read sms and store it

                        if(strncmp("Water on",msg1,8)==0)
                        {
                                Water=1;
                                Status();
                        }
                        else  if(strncmp("Water off",msg1,9)==0)
                        {
                                Water=0;
                                Status();
                        }
                        else  if(strncmp("Window on",msg1,9)==0)
                        {
                                Window=1;
                                Status();
                        }
                        else  if(strncmp("Window off",msg1,10)==0)
                        {
                                Window=0;
                                Status();
                        }
                        else  if(strncmp("Status",msg1,6)==0)
                        {
                                Status();
                        }
                        else
                        {
                        SMSString("AT+CMGS=\"");
                        SMSString(phone);
                        SMSString("\"\n\r");
                        delay_sms(1000);
                        SMSString("Wrong Command");
                        SMSString("\n\r");
                        delay_sms(1000);
                        }
                SMSString("AT+CMGD=1\r");
                delay_sms(1000);

                IE=0X00;   // Disable serial interrupt
                delay_sms(1000);
                }
        while(1);
}
void init(void)
{
        j=0;
        bufcounter=0;
        TL1=0XFD; //9600 @ 11.0592
        TH1=0xFD;
        TMOD=0x20;
        SCON=0x50;
        TR1=1;
}
void SMSString(unsigned char* text) //function to send SMS using GSM modem
{
        while (*text)
        {
                tx0(*text++);
        }
}
void tx0(unsigned char x) //send data to serial port 0
{
        EA=0;
        SBUF=x;
        while(TI==0);
        TI=0;
        EA=1;
}
void delay_sms (unsigned int count)
{
        unsigned int i;
    while(count)
        {
       i = 115;
       while(i>0) i--;
       count--;
        }
}
void init_modem(void)
{
        Window=0;
        Water=0;
        SMSString("AT\r"); // AT commands to initialize gsm modem
        delay_sms(1000);

        SMSString( "ATe0\r"); // turn off echo
        delay_sms(1000);

        SMSString( "AT&W\r"); // save settings
        delay_sms(1000);

        SMSString( "AT+CMGF=1\r"); // select text mode for sms
        delay_sms(1000);

        SMSString( "AT+CNMI=2,1,0,0,0\r"); // notification of new sms
        delay_sms(1000);

        SMSString( "AT+CMGR=1\r"); // AT command to read sms
        delay_sms(1000);
}
void Status(void)
{
        unsigned char tmp10 = sprintf(msg1 ,"Water is %s and Window is %s\n" , Water, Window);
        SMSString("AT+CMGS=\"");
        SMSString(phone);
        SMSString("\"\n");
        delay_sms(1000);
        //SMSString(tmp10);
        SMSString("\n\r");
        delay_sms(1000);
}
enum States
{
    STATE_IDLE,
    STATE_FIND_CMT,
    STATE_CMT_GET_NUMBER,
    STATE_CMT_GET_COMMA,
    STATE_CMT_GET_MSG_START,
    STATE_CMT_GET_MSG,
}
state = STATE_IDLE;
const unsigned char* pattern;
int ch;

void process_modem_character(unsigned char*msg) {
    switch (state) {
        case STATE_IDLE:
            if (msg == '+')
                        {
                state = STATE_FIND_CMT;
                pattern = "\+CMTI\: \"SM\",1\r+CMGR: \"REC UNREAD\"\,\"";
            }
            break;
        case STATE_FIND_CMT:
            if (*pattern != msg)
                        {
                state = STATE_IDLE;
            }
                        else
                        {
                pattern++;
                if (*pattern == '\0')
                                {
                    state = STATE_CMT_GET_NUMBER;
                    ch = 0;
                }
            }
            break;
        case STATE_CMT_GET_NUMBER:
            if (msg == '\"')
                        {
                state = STATE_CMT_GET_COMMA;
            }
                        else if (ch >= sizeof(phone))
                        {
                // Too long phone number :(
                state = STATE_IDLE;
            }
                        else
                        {
                                ch++;
                phone[ch] = *msg;
                phone[ch] = '\0';
            }
            break;
        case STATE_CMT_GET_COMMA:
            if (msg == ' ')
                        {
                ;    // Ignore white space
            }
                        else if (msg == ',')
                        {
                state = STATE_CMT_GET_MSG_START;
            }
                        else
                        {
                // Invalid character received
                state = STATE_IDLE;
            }
            break;

        default:
            // Invalid state.
            state = STATE_IDLE;
    } // switch
} // process_modem_character
void clear(void)
{
        unsigned char a;
        for(a=0;a<100;a++)
        msg1[a]=0x00;
}

Also i get error C214: illegal pointer conversion

void Status(void)
{
        unsigned char tmp10 = sprintf(msg1 ,"Water is %s and Window is %s\n" , Water, Window);
        SMSString("AT+CMGS=\"");
        SMSString(phone);
        SMSString("\"\n");
        delay_sms(1000);
        SMSString(tmp10);
        SMSString("\n\r");
        delay_sms(1000);
}

and i don't really understand why.