Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Register Log in
  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

GSM modem interfacing to AT89C51

Status
Not open for further replies.
A

amit251291

New Member
hello,
I want to interface GSM modem to 8051. As other part of my project is in assembly language i am preferring the same programming language for this part too! I am NOT using any LCD to display Commands and responses.
Can someone please share the ASSEMBLY LANGUAGE CODE TO SEND SMS BY USING GSM MODEM AND MICROCONTROLLER. please?

Thank you :)
 
Last edited:
I think once you read the AT SMS commands for your specific modem, then all will come clear. I have C routines to set up a uBlox modem and send SMS.
Pretty easy to convert to asm as it's the commands needed that are hard to determine. create the message in an array, terminate with NULL and send sequentionally until NULL detected. Don't forget the CRTL(Z) or ASCII 26 at the end.
If you do not know how to write a string to XRAM and then sequentially send it to a port in asm then you are stuffed. That is basic computing.

/*********************************************************/
void sms_message(unsigned char *num,unsigned char *data)
/*********************************************************/
{
unsigned char str[20]={"AT+CMGS=,"};
unsigned char i;
i=0;


sprintf(modem,"AT+CMGS=");
send_modem(&modem[0]);


WriteChar(port,'"');
i=0;
while (*(num+i) != '\0') // NULL
{
WriteChar(port,(unsigned char)toupper(*(num+i)));
i++;
}
WriteChar(port,'"');
WriteChar(port,CARRIAGE_RETURN);

i=0;
delay(0.5f);



while (*(data+i) != '\0') // NULL
{
WriteChar(port,(unsigned char)toupper(*(data+i)));
i++;
}

WriteChar(port,26);



}
/*************************************************/
void send_modem(unsigned char *ch)
/*************************************************/
{
unsigned char i;

i=0;

while ((*(ch+i)) != '\0') // NULL
{
WriteChar(port,(unsigned char)toupper(*(ch+i)));
i++;
}

}
/*********************/
void modem_init(void)
/*********************/
{
int i;

delay(0.5f);
printf("\n\rInitialising Modem.......");
modem_buffer_pointer=0;
sprintf(modem,"AT\r");
send_modem(&modem[0]);
delay(1.0f);
if (modem_buffer_pointer==0)
{
printf("\n\rModem Not Responding");
// done();
}
//return;
sprintf(modem,"ATE0\r"); /*No echo */
send_modem(&modem[0]);
delay(1.0f);

sprintf(modem,"ATS10=1\r"); /*immediate NO CARRIER */
send_modem(&modem[0]);
delay(1.0f);


sprintf(modem,"ATS0=1\r"); /*auto answer */
send_modem(&modem[0]);
delay(1.0f);


sprintf(modem,"AT+CMGF=1\r"); /*sms init */
send_modem(&modem[0]);
delay(1.0f);

sprintf(modem,"AT+CLIP=1\r"); /*clid init */
send_modem(&modem[0]);
delay(1.0f);

sprintf(modem,"AT+CNMI=0,2,0,0,0\r"); /*sms init with auto alert*/
send_modem(&modem[0]);
delay(1.0f);
for (i=0;i<100;i++)
{
printf("%c",modem_buffer);
}
delay(1.0f);

modem_buffer_pointer=0;

}
 
Thank you so much for this code.
i had prepared my code before seeing your reply.
i am posting my code here. its not showing any syntax error. but i am not sure whether its logically correct or not :confused:
So please go through this code once and suggest me corrections if any :)

Code: 
ORG 0000H
		MOV TMOD,#20H	   		//TIMER 1, MODE 2
		MOV TH1,#-3				//9600 BAUD RATE
		MOV SCON,#50H			//8 BIT, 1 STOP, EN ENABLED
		SETB TR1
				
		MOV DPTR,#MSG1
		ACALL H1
		ACALL DELAY
		MOV DPTR,#MSG2
		ACALL H1
		ACALL DELAY
		MOV DPTR,#MSG3
		ACALL H1
		ACALL DELAY
		MOV DPTR,#MSG4
		ACALL H1
		ACALL DELAY
		MOV DPTR,#MSG5
		ACALL H1
		ACALL DELAY
H1:  	CLR A
		MOVC A,@A+DPTR
		JZ B1
		ACALL SEND
		INC DPTR
		SJMP H1
B1:
		RET
SEND: 	MOV SBUF,A
H2: 	JNB TI,H2
		CLR TI
		RET
DELAY:  MOV R3,#50H
HERE2:  MOV R4,#50H
HERE:	DJNZ R4,HERE
		DJNZ R3,HERE2
		RET
	

ORG 300H
MSG1: DB "AT",0DH
	  DB 0H
MSG2: DB "AT+CMGF=1",0DH
	  DB 0H
MSG3: DB "ATE=0",0DH
      DB 0H
MSG4: DB "AT+CMGS=",'"8149111111"',0DH
	  DB 0H
MSG5: DB "TEXT",0X1A
	  DB 0H

	  END
 
Hi amit251291,
I would like to suggest 2 things here,

1st is that connect microcontroller circuit to your PC then go to Hyper terminal, set baud rate to 9600. Then check if these AT commands are received on hyper terminal.... If not then check your hardware.

2nd thing, at the end of the msg1, msg2,3,4,5 you have sent 0DH.... I used to send 0AH, 0DH... try with this....
 
hello rushi53,
i din't get what 0AH, 0DH stand for? 0DH is for ctrl+m.
Can you please share your code here?
Thank you :)
 
amit251291 said:
hello rushi53,
i din't get what 0AH, 0DH stand for? 0DH is for ctrl+m.
Can you please share your code here?
Thank you :)
Click to expand...

0Ah is line feed and 0Dh is carraige return.... Modems only need 0Dh.. You code is fine.

The only issue you may find is that modems are usually hardware handshake from the off. So you may need to hook the modem up to a PC and configure for 3 wire hook up...
 
amit251291 said:
Thank you so much for this code.
i had prepared my code before seeing your reply.
i am posting my code here. its not showing any syntax error. but i am not sure whether its logically correct or not :confused:
So please go through this code once and suggest me corrections if any :)

Code: 
ORG 0000H
		MOV TMOD,#20H	   		//TIMER 1, MODE 2
		MOV TH1,#-3				//9600 BAUD RATE
		MOV SCON,#50H			//8 BIT, 1 STOP, EN ENABLED
		SETB TR1
				
		MOV DPTR,#MSG1
		ACALL H1
		ACALL DELAY
		MOV DPTR,#MSG2
		ACALL H1
		ACALL DELAY
		MOV DPTR,#MSG3
		ACALL H1
		ACALL DELAY
		MOV DPTR,#MSG4
		ACALL H1
		ACALL DELAY
		MOV DPTR,#MSG5
		ACALL H1
		ACALL DELAY
H1:  	CLR A
		MOVC A,@A+DPTR
		JZ B1
		ACALL SEND
		INC DPTR
		SJMP H1
B1:
		RET
SEND: 	MOV SBUF,A
H2: 	JNB TI,H2
		CLR TI
		RET
DELAY:  MOV R3,#50H
HERE2:  MOV R4,#50H
HERE:	DJNZ R4,HERE
		DJNZ R3,HERE2
		RET
	

ORG 300H
MSG1: DB "AT",0DH
	  DB 0H
MSG2: DB "AT+CMGF=1",0DH
	  DB 0H
MSG3: DB "ATE=0",0DH
      DB 0H
MSG4: DB "AT+CMGS=",'"8149111111"',0DH
	  DB 0H
MSG5: DB "TEXT",0X1A
	  DB 0H

	  END
Click to expand...

Your code looks workable. Check the assembler directive for DB. Some will do just that and allow a single byte in the definition whereas you are looking at a reserving a string. KEIL handles this correctly, but I have come across others that don't.

As already said, hook up hyperterm and check what is being sent to the modem is correct. You may also want to start the whole conversation with AT and check it returns OK. Most autobaud modems use this to determine the speed you are sending at.
 
Thank you WTP Pepper and Ian Rogers

I have just made a correction in program. i put

Stay: sjmp Stay

just after the last ACALL DELAY command. This i did by thinking that microcontroller would enter in subroutines after execution of the last ACALL DELAY command. whether this correction is right?


So you may need to hook the modem up to a PC and configure for 3 wire hook up...
Click to expand...
I dint get this.. :( I had connected my modem only to PC by using DB9 connector.. Sent AT commands from hyper terminal and MODEM was working fine..
 
hello Ian Rogers ,

Actually my modem is sim300. When i see hardware of this modem, i saw 1 MAX232 IC on it which is further connected to RS232 Female connector. Also only 3 pins are conneted between MAX 232 and RS232 connector i.e TXD, RXD, and ground. I can see this on PCB. In short, only TXD, RXD, and ground come out of the modem via RS232. Other pins of RS232 connector have been left unconnected..
 
You can fool the modem by wiring certain CTS/DTR lines together to avoid hardware handshaking. I cannot remember exactly what needs doing on a DB9, but can find out if wanted.

Ian Rogers. Yep correct. You need to run these devices off a good PSU or as I have done before, a slowish charging Li-Ion/Li-Pol cell as they can supply the high instantaneous current required. Especially when a call is being made or the device is registering on the network. Any other cell technology apart from maybe lead acid (bulky) is impractical. Mobile phones use Li-ion/Li-Pol battery technology for a reason.

A poor power supply can lock up a modem and send you looking for a protocol solution that isn't needed.
 
hello, Ian Rogers & WTP Pepper,

Actually my modem came with a adapter, so i don't think that there is problem of supply... :|

The last program which i have posted here, is not working.



GSM modem has following on-board connections:

MAX232----->> RS232 (Female connector)

pin 7 ---> Pin 2
pin 8 ---> Pin 3

So i have done following connections after this:

RS232 (Female connector) --->> RE232(PCB male connector ) ( This o did because it was difficult to take connections from on-board Female connetor)

I took out following pins from RS232 male connector and connected to microcontroller:

RS232(PCB male connector ) ---> AT89C51
Pin 2 --> Pin 11
Pin 3--> Pin 10
Pin 5 Grounded.

Rest AT89C51 connetions:

Crystal oscillator 12 Mhz.
EN (Pin 31) -VCC
Pin 40-- VCC
Pin 20-- Gnd


Are these connetions are correct??
why my program is not working ??
 
GSMCIRCUIT1.jpg

here is my circuit diagram... please let me know where i am going wrong...
 
Status
Not open for further replies.

Similar threads

K
  • Article
Gsm sim900 shield stopped working ||interfaced with 8051
Replies
0
Views
8K
koketso
K
D
AT89C51- Datasheet
Replies
10
Views
8K
Djsarkar
D
F
problem to understand how to divide two 16 bits number in 8051 microcontroller
Replies
1
Views
9K
rjenkinsgb
rjenkinsgb
K
what is the function that convert string to integer?
Replies
4
Views
6K
charlesli
C
S
GSM Interfacing of 8051
Replies
3
Views
2K
bilalmalik
B

Latest threads

New Articles From Microcontroller Tips

Back
Top