| View previous topic :: View next topic |
| Author |
Message |
vjn86
Joined: 12 Oct 2009
Posts: 11
|
| operator/operand error when comparing AT command |
 Posted: Mon Oct 12, 2009 10:43 am |
 |
|
Hi there. I have tried to do a simple coding to read message from gsm modem and send another message as an acknowledgment to pre determined number. The error that I get in ccs compiler says that + and " " symbol cannot be use as it is a operand but the problem is the data transmitted to pic is contains both + and "" sign... [ +CMTI: "SM",1 ]
This is my coding. I hope someone could guide me on this.
| Code: | #include <16f876a.h>
#device adc=10
#use delay(clock=20000000)
#fuses hs,nowdt,nolvp,noprotect
#use rs232(baud=9600,xmit=pin_c6,rcv=pin_c7, parity=n)
byte mystat=0;
char mydata;
char +CMTI: "SM",1
void main()
{set_tris_c(0x80);
do
{
if (kbhit())
{ mydata=getch();
mystat=1;
}
if (mystat==1)
{
// compare data
if(mydata=='+CMTI: "SM",1')
{ printf("at+cmgf=1\r\n");
delay_ms(500);
printf("at+csmp=17,168,0,0\r\n");
delay_ms(500);
printf("at+cmgs=\"+60136240915\"\r\n");
delay_ms(3000);
printf("hey ");
putc(0x1A);
delay_ms(10000);
}
else
break;
}
}while(1);
}
|
|
|
 |
PCM programmer
Joined: 06 Sep 2003
Posts: 21708
|
|
|
Wayne_
Joined: 10 Oct 2007
Posts: 681
|
|
| Posted: Thu Oct 15, 2009 2:12 am |
|
|
You also need to read up on C char arrays and strings.
This :-
char +CMTI: "SM",1
is not possible.
This :-
if(mydata=='+CMTI: "SM",1')
Will also fail.
The single quote is used to represent a single char as in
char a = 'a';
The double quote is used to create a string BUT the string must be assigned to a char array and the array MUST have enough space for the hidden null terminating character '\0'
char str[17] = "This is a string";
To create a string that contains double quotes as in your case you use the escape char \ This tells the compiler to ignore the next char and just use it as is. A little vague there but what I mean is if you start a string with " then the next time the compiler sees a " it will think it is the end of the string. You need the compiler to ignore that " and in your case the next one so that they are part of the string. If you see what I mean ?
char myStr[] = "+CMTI: \"SM\",1";
This will create a var called myStr which will contain the string
+CMTI: "SM",1
Hope this helps. |
|
|
vjn86
Joined: 12 Oct 2009
Posts: 11
|
|
| Posted: Sat Dec 05, 2009 8:26 am |
|
|
thanks guys.. this really helps ...
Wayne : when i was exploring ur tips i found that :
char myStr[] = "+CMTI: \"SM\",1"; will produce (+CMTI: "SM",) only... but with an addition of /n in the coding : "+CMTI: \"SM\",1/n"
I was able to get output as expected. I wonder how /n changes the output... anyway thanks man... |
|
|
Wayne_
Joined: 10 Oct 2007
Posts: 681
|
|
| Posted: Mon Dec 07, 2009 3:12 am |
|
|
"/n" places a newline char[10] charater at that point. The device you are talking to will use the nl newline char as the end of the command.
Some devices need "/r/n" char[13] char[10] (cr carridge return, nl newline) to indicate the end of the command.
I am not sure how you debuged the string to determine that it only contained (+CMTI: "SM",) but I expect that it was the way you did this that made it look like it didn't contain the rest!
Either that or there is a bug in CCS! |
|
|
vjn86
Joined: 12 Oct 2009
Posts: 11
|
|
| Posted: Thu Dec 10, 2009 12:53 pm |
|
|
| Ayte.. thanks man... |
|
|
vjn86
Joined: 12 Oct 2009
Posts: 11
|
|
| Posted: Sun Mar 21, 2010 12:50 pm |
|
|
| Wayne: I think there is an error with my pic circuit. Whenever I print a string using c6 and c7, it will omit the last two characters. But somehow I am still able to send send at command and get its response. However I am able to get the string without being trimmed if I defined other than c6 and c7 for rs232...hmm...weird... |
|
|
|
FAQ 
Search
Register
Profile 
Log in to check your private messages 
Log in
