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i can't recieve information from gsm modem


Moderators: Ajay, Junied , abbas1707, Arun Kumar V, pdi33, Shailesh NAYAK, ۞ TPS ۞, shyam, sashijoseph

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agnostos

Thu May 15 2008, 11:04PM

Registered Member #7875

Joined: Thu May 15 2008, 10:50PM

Posts: 3
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hello i am a student and i have a project to do with stk500 and gsm modem (siemens mc35).
i have connected the gsm modem with avr. i use printf to send a message and work perfectly but when i use scanf to read from gsm modem nothing happend why???
for example if i run this code
while(1)
{
printf("AT \r\n");
delay_ms(10);
/*Waiting for the response*/
scanf("%s", myData);
PORTB.0 = 1;
delay_ms(1000);
printf("at+cmgs=6938699188");
putchar( CR ); //CR
putchar( LF ); //LF
delay_ms(1000);
printf("%s",myData);
putchar(CTRLZ);
delay_ms(1000);
// if (myData[0] == 'O')
PORTB.0 = 0;
break;
}

i get message writing "AT" but this isn't write i must get "OK".
what must i change to read from gsm modem correct???
please help me time pressure me i have to finish my project until this Monday.
thanks....

shyam

Fri May 16 2008, 02:54AM

Registered Member #2984

Joined: Mon Aug 06 2007, 11:33AM

Posts: 710
Thanked 104 times in 100 posts

u will have to stop the echo first
"ATE0\r\n"

now if using scanf(), why r u using delay_ms(10) ??
no need at all..
and the syntax for sms should be ( i think)
at+cmgs="6938699188"
please confirm by connecting modem directly to PC via hyperterminal and verify both the commands
1.at+cmgs=6938699188
2.at+cmgs="6938699188"

considering the first command works then=>try modifying the code like this

CODE:

printf("ATE0\r\n");

while(1)

{

printf("AT \r\n");

scanf("%s", myData);

PORTB.0 = 1;

printf("at+cmgs=6938699188\r\n");

printf("%s\r",myData);

putchar(CTRLZ);

delay_ms(1000);

// if (myData[0] == 'O')

PORTB.0 = 0;

break;

}

now if first command does not works then try the second and modify the code as

CODE:

printf("ATE0\r\n");

while(1)

{

printf("AT \r\n");

scanf("%s", myData);

PORTB.0 = 1;

printf("at+cmgs=\"6938699188\"\r\n");

printf("%s\r",myData);

putchar(CTRLZ);

delay_ms(1000);

// if (myData[0] == 'O')

PORTB.0 = 0;

break;

}

u see most of the time scanf itself waits until it receives "\r" so u need not wait...

check and let us know if it works..
till then

lProgress is not made by early risers or hard workers, but by LAZY people, trying to find easier ways to do the same........

agnostos

Sat May 17 2008, 02:48AM

Registered Member #7875

Joined: Thu May 15 2008, 10:50PM

Posts: 3
Thanked 0 times in 0 posts

the gsm modem doesn't accept the \" it works with out that. i try your code but i have the same problems the message is null. why???
please help me time pressure me and i don't know what to do...

agnostos

Sat May 17 2008, 03:08AM

Registered Member #7875

Joined: Thu May 15 2008, 10:50PM

Posts: 3
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i am afraid that my connection is error. i bought a null modem cable. and it is female in both sides. and i connect null modem. with this way
null modem - avr
2 -------> 3
3 -------> 2
5 -------> 5
i do the same from other side (null modem with gsm modem)
is my connection good???

sashijoseph

Sat May 17 2008, 05:31PM

Registered Member #5870

Joined: Mon Feb 04 2008, 06:26PM

Posts: 501
Thanked 114 times in 107 posts

See,what you need to do is connect Tx of modem to Rx of AVR and Rx of modem to Tx of AVR.(and both their grounds as well)
Check your null modem cable.....if pin2,pin3 at one end is connected to pin3,pin2 at the other end,then this is how you connect......

Let there be music........

shyam

Sat May 17 2008, 09:37PM

Registered Member #2984

Joined: Mon Aug 06 2007, 11:33AM

Posts: 710
Thanked 104 times in 100 posts

u said that the mesaage is NULL...

does that mean u not recving message ?? or u recving msg with nothing to display??

lProgress is not made by early risers or hard workers, but by LAZY people, trying to find easier ways to do the same........

trinadha

Sat Aug 09 2008, 06:01AM

Registered Member #9699

Joined: Sat Aug 09 2008, 05:49AM

Posts: 1
Thanked 0 times in 0 post

guys can u tell me how to recive area notification of gsm area onto a microprocessor

Shailesh NAYAK

Tue Aug 12 2008, 11:11PM

Registered Member #2498

Joined: Mon Jul 23 2007, 01:20AM

Posts: 39
Thanked 9 times in 7 posts

Hi,
receiving SMS will give first unsolicited SM indication with message index no.
first use AT+CNMI=2,1,0,0,0 which will give you unsolicited indication AT+CMTI: "SM",1
with message no. index.
as you receive this, use AT+CMGR=1 ( 1 is nothing but an Index no.).

Best Regards

Shailesh S. NAYAK