reading sms from gsm modem and comparing with predefind one

[td]

hi,

in our project, we are using pic 18f and modem sim 300.and we are using c18 compiler.in that i have written program for sending and receiving sms through gsm modem.when i use the AT command for reading sms, i m getting like this

 

AT+CMGR=1
+CMGR: “REC READ”,”+918108111649″,,”12/07/22,14:24:11+22″
Hello

OK

 

here i have to read the sms “Hello”, which comes before “OK”.and compare it with a predefined string. i write for parsing string.but i m not getting the word “Hello”. here is codes…

 

<code>

putrsUSART(“ATnr”);
putrsUSART(“AT+CMGF=1”);
putcUSART(0x0D);
Delay10KTCYx(500);
putrsUSART(“AT+CMGR=1”);
putcUSART(0x0D);
Delay10KTCYx(500);

 if(PIR1bits.RCIF)  
{
for(i=0;i<5;i++)

    a=getcUSART();

}
putsUSART(a);
 

</code>

while exicuting this, i m getting “a ” as some srange characters like ?2k> or ?ï2oÈ

how can i extract the messange hello?? please help me to solve this problem.

thank you

[Manikandan]

Hi,

   I think delay may be the problem. please check and correct the delay.

Thank you,

Manikandan A

[td]

Thank you for reply.

 

i have reduced the delay .and took the buffer like a[50],

in both case stange characters are coming.

[td]

thanks for reply..

 

what you mean by

if(Rcv_Byte==arr1[count]||count>5)

 

is that necessary to set flag??

[td]

thank you 

 

here your program is for getting hello only..but the modem response is 

 

+CMGR: “REC READ”,”+918108111649″,,”12/07/22,14:24:11+22″
Hello

OK

so 1st we have to read these whole string.how can i read this whole sting?

i used some inbuilt functions for reading charecter wise.but some strange characters are coming.here is my code.

 

for(i=0;i<70;i++)

    a=getcUSART();

}
putsUSART(a);

how can i input that whole sting to pic?

 

 

 

[td]

i changed the steps, but i m not getting the string…

+CMGR: “REC READ”,”+918108111649″,,”12/07/22,14:24:11+22″
Hello

OK

 

here is the pgm……

 

putrsUSART(“AT+CMGR=1”);
putcUSART(0x0D);

while(BusyUSART());
gets(a);
Delay1KTCYx(75);
putsUSART(a);

}

 

void gets(char *buffer)
{
  unsigned char data;
 do
  {
    while(!DataRdyUSART());// Wait for data to be received
    data = getcUSART();                         
    *buffer = data;
    buffer++;              // Increment the string pointer
  }
while(data!=’K’);
*buffer=’’;
}

 

please help me to print the modem response….

 

thank you

[td]

when i connected pic and levelconverter to pc, the above program is working fine.but, when i connected modem and pic, i can send sms.and modem can read the sms.but when the modem execute the AM+CMGR=1 command, the modem response string is not going to pic. please help me to solve the problem..

[Amrith]

Hi td,

Correct your command mentioned AM+CMGR=1 as AT+CMGR = 1,

[td]

in my program, i have written like this

AT+CMGR = 1

when i re-write in last post, AT changes to AM. sorry for the mistske.

 

please give me one solution to my problem.how can i give modem response to pic?

[Amrith]

Hi,

As you send command AT+CMGR =1 to GSM modem, you will receive the message data. you might not capturing the data properly in the buffer. Avoid delay functions in between this communication.

 

Important Note: Take care that you are connecting Tx pin of GSM module to Rx pin of DB9 serial cable & Rx pin of GSM module to Tx pin of DB9 serialcable.

 

[td]

i m not giving the delay aftr AT+CMGR=1

 

 

putrsUSART(“AT+CMGR=1”);
putcUSART(0x0D);

while(BusyUSART());
gets(a);

 

 

and i connected modem and pic directly- rx of pic to tx of modem and vice verse. but then also nothing is going to tic.ie, response of modem is not going to pic

[Amrith]

Hey,

You must use level converter between your PIC & GSM modem, better share your schematics to verify how you are connecting..

[td]

thank for reply..

my pic is working at 3.3v and modem at 4v.so why should i use level converter? i connected rx,tx pin of modem to tx,rx pin of pic.

and connected level converter(max232) parallel to pic(used only for watching in hyper)

 

i can send sms from modem to mobile.and modem can read the sms..but the response of the modem is not going to pic

 

 

[td]

hi

 

in this project pic is not getting the response from modem.

i just write the AT command, then modem is responding OK.but pic is not getting that response.i tried to print the response from modem.but i m not getting any output.

when i checked pic and hyper, its working and checked modem and hyper.that is also working. ang when i connected pic and gsm modem, modem is getting all the commands from controller.and i can send sms from modem to mobile.but in case of sms reading, modem is responding for AT+CMGR=1.

but pic is not getting that response.ie,from pic to gsm, transmission is ok.but from gsm to pic, not working.

 

please help me to sove this problem

[Amrith]

you need a level converter between PIC & GSM modem because the GSM modem has a level converter inside which converts ttl to rs232 level, so you should not connect GSM modem directly to controller, you got to use level converter to convert these rs232 levels to ttl levels again.

 

[Author]

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