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aldinlapinig
Joined: 16 Dec 2005
Posts: 22
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| GSM with PIC interface Help needed!!! |
 Posted: Tue Aug 08, 2006 2:33 am |
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Hello all,
I am developing a program that will interface a GSM module with PIC through RS232. Can anybody who have tried doing this give me an idea on how I could analyze the reponse from the GSM module evry after I send an AT command to the it? To make this clearer, I'll explain the process I did which unfortunately stuck me up because I couldn't come up with a better algorithm to analyze the reponses of the GSM. Here are what I did: (actually, what the program will do)
* I send AT command to the gsm module.
* I wait for a coressponding time (depending on the command I send) for the response to be received in the serial input buffer.If data is available within the specified time, I read it. Otherwise communication error will be declared.
Example:
tx : "AT"<cr>
rcv : AT<cr><cr><lf>OK<cr><lf>
tx : "AT+IPR=38400"<cr>
rcv : AT+IPR=38400<cr><cr><lf>OK<cr><lf>
tx : "AT+CPIN"<cr>
rcv : AT+CPIN<cr><cr><lf>+CPIN: READY<cr><lf><cr><lf>OK<cr><lf>
Now, the problem I am encountering is that, the module would give me different responses on different AT commands (which is normal) and I don't know how to make a better algorithm for my program to get a certain part of the response I need. I got no problem with the first 2 of the examples above because I only need to get the "OK" status. The problem is detecting other responses and status of the communication like device is "READY" message is "READ" or "UNREAD", the "ERROR ###"... and so on... Is there any other way aside from parsing the data I receive? It would create a very long program to extract the status of the communication just to extract "OK", "READY", "REC READ", ERROR", the "ERROR ###"... Hope I stated the problem clearly enough... thanx guys. Need your help on this.
Have a good day!
kind regards,
aldin |
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jaime
Joined: 25 Nov 2005
Posts: 56
Location: Porto - Portugal
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| Posted: Tue Aug 08, 2006 3:57 am |
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I have a litle system that uses a cell phone to control a light.
I use state machine to do the job. I use a outine to read rx interrupt and then analyse what the cell phone sends...
This is my rda routine
| Code: | #int_rda
void trata_rda()
/*
two examples of what we can receive
case 1:
LF CR O K CR LF
case 2:
LF CR + C P B R: xxxxxxxxxxxxxxx CR LF CR LF O K CR LF
the program must detect only the LF if it's not CR or LF the program puts in the
buffer[x]
*/
{
temp=getc();
if(temp==0x0A)
{
if(!start_pack)
{
start_pack=true; //start of message
x=0;
}
else if(start_pack && buffer[0]=='+' && !middle_pack && !ok_pack)
middle_pack=true;
else if(start_pack && buffer[0]=='+' && middle_pack && !ok_pack)
ok_pack=true;
else
{
receive_pack=true; //we got the message
buffer[x]=0;
//uncomment the next line to debug
//printf("buffer=%s\r",buffer);
}
}
else if(temp!=0x0A && temp!=0x0D && !ok_pack)
{
buffer[x]=temp;
x++;
}
} |
This is my debug function
| Code: | void debug_data()
{
/*
when receive something in the buffer[] we debug to know what's inside
we can have in buffer[] 2 things.
case 1:
short message like:
OK, RING, ERROR, BUSY, NO DIAL TONE.
this type of message only actives a flag
case2:
Long message like:
+CLCC:...
+CPBR:...
this type of message we must decode inside the message
*/
if(!middle_pack)
{
if (buffer[0]=='O') //receive OK
ok=true;
else if(buffer[0]=='R') //receive a ring
ring=true;
else if(buffer[0]=='A') //receive a echo
ok=true;
else
error=true; //receive another short message
}
else
{
//ve se o que recebeu é um +clcc
if(buffer[2]=='L' && buffer[3]=='C' && buffer [4]=='C')
{
clcc=true;
incognito=true; //é um clcc. pesquisa a flag recebida
for(f=1;f<=x;f++) //the caller number is inside " "
{
if(!achei && buffer[f]==0x22 ) //procura a primeira aspa 0x22 = "
achei=true;
else if(achei && buffer[f]!=0x22)//estamos dentro das aspas. guarda o
{ //numero chamador
chamador[i]=buffer[f];
i++;
chamador[i]=0;
incognito=false;
}
else if(achei && buffer[f]==0x22)//segunda aspa indica q acabou o nume
break; //ro chamador
}
}
else if(buffer[2]=='P' && buffer[3]=='B' && buffer [4]=='R')
{
cpbr=true;
for(f=1;f<=x;f++) //the number is inside " "
{
if(!achei && buffer[f]==0x22 ) //0x22 = "
achei=true;
else if(achei && buffer[f]!=0x22)
{
permitido[i]=buffer[f];
i++;
permitido[i]=0;
}
else if(achei && buffer[f]==0x22)
break;
}
}
else if(buffer[2]=='P' && buffer[3]=='B' && buffer [4]=='S')
{
cpbs=true; //the lengh of the card is after,
for(f=1;f<=x;f++)
{
if(!achei && buffer[f]==0x2C ) //0x2D = ,
achei=true;
else if (!encontrei && achei && buffer[f]==0x2C)
encontrei=true;
else if(encontrei)
{
maximo[i]=buffer[f];
i++;
maximo[i]=0;
}
}
sim=atoi(maximo); //convert ascii to decimal
}
}
start_pack=middle_pack=ok_pack=false; //reset das flags de controlo
receive_pack=false;
achei=encontrei=false;
i=f=0;
x=0;
buffer[0]='0';
i=0;
} |
Hope it helps |
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