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You are here: Home / Topics / Gsm modem with AT89C51

Gsm modem with AT89C51

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Microcontroller › 8051 › Gsm modem with AT89C51

  • This topic has 9 replies, 5 voices, and was last updated 12 years, 2 months ago by muneebullashariff.
Viewing 10 posts - 1 through 10 (of 10 total)
  • Author
    Posts
  • January 11, 2013 at 2:54 pm #2061
    amit kulkarni
    Participant

    Can you please tell me how to interface GSM modem (sim 300) to microcontroller (AT89C51)to send sms?

     

    I need assembly program for the same..

     

    I have prepared my own but it is not working:

     

    here it is:

     

    <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
    STAY: SJAMP STAY
    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<code>

     

    connections:

    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 ?? 

     

     

    can any one tell me assembly program to interface the same?

    January 11, 2013 at 5:08 pm #8932
    AJISH ALFRED
    Participant

    Hi Amith,

    Why don’t you post a diagram? It would have been more easy for us to find out the problem.

    January 13, 2013 at 8:12 am #8939
    amit kulkarni
    Participant

     

    we have drawn this circuit in paint. Drawing is not very good.
    RS232 male connector is connected just to make it easy to make the connections…
     
    Waiting for your reply 

    wysiwyg_imageupload:7214:

    January 13, 2013 at 5:20 pm #8943
    AJISH ALFRED
    Participant

    The connection is alright. Make sure that you’ve made the ground common for both the MCU and the modem including max232.

    January 14, 2013 at 9:03 am #8948
    amit kulkarni
    Participant

    The ground is common no problem with it…. :|

    why it is not working?

    January 14, 2013 at 11:55 am #8950
    nidhin.k
    Participant

    hi….. 

     

       please use 11.0592MHz crystal…. it will work

    January 14, 2013 at 12:27 pm #8952
    amit kulkarni
    Participant

    it is not shown here in this diagram,but  i have connected it :)

    February 14, 2013 at 11:10 am #9138
    RAJI G
    Participant

    first  verify  ur serial communication program and then proceed..

    February 14, 2013 at 4:18 pm #9140
    amit kulkarni
    Participant

    This problem has been Solved :)

     

    Thank you all :)

    April 26, 2013 at 3:13 pm #9586
    muneebullashariff
    Participant

    what was the problem???

     

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