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ILLIAS28
Joined: 11 Jan 2011
Posts: 42
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| help in strings comparison |
 Posted: Mon Mar 17, 2014 8:33 pm |
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Could you please help me to find what's wrong with the following code. I am trying to send AT commands to test my gsm which is connected to pic16f876 through TX and RX pins. But when compiling I always get the following error:
Attempt to create a pointer to a constant
many thanks in advance.
here is the code:
| Code: |
#include <16F876.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#fuses XT NOWDT NOPUT NOPROTECT BROWNOUT NOLVP NOCPD NOWRT NODEBUG
#use delay(clock=4000000) // you must use this line becuse the LCD.C use //the delay_us() functions
#use rs232(baud=9600,xmit=pin_c6,rcv=pin_c7)
//#pragma use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7)
#define use_portb_lcd TRUE
#include <lcd.c>
void main()
{
int i;
char buffer[];
char rec_data;
SET_TRIS_A( 0xFF );
SET_TRIS_B( 0x00 );
SET_TRIS_C( 0x00 );
i=0;
lcd_init();
lcd_putc('\f');
lcd_gotoxy(1,1);
printf(lcd_putc,"hallo");
DELAY_ms(3000);
for(;;)
{
lcd_putc('\f');
printf(lcd_putc,"pressez bouton");
if(input(PIN_A0))
{
printf("at\r"); //test gsm
do
{
rec_data=getc();
}
while(rec_data!='\n'); //wait for gsm response
do
{
rec_data=getc();
buffer[i]=rec_data; //save response in a string
i++;
}
while(rec_data!='\n');
if(strcmp(buffer,"ok",2 )!=0) //see if response is "ok"
{
lcd_putc('\f');
printf(lcd_putc,"error...");
}
lcd_putc('\f');
printf(lcd_putc,"Error");
}
}
} |
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i am newbe |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Mon Mar 17, 2014 9:15 pm |
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| Quote: | But when compiling I always get the following error:
Attempt to create a pointer to a constant |
That problem can be fixed by adding the line shown below:
| Quote: | #include <16F876.h>
#device PASS_STRINGS=IN_RAM |
But your program has many other problems.
| Quote: |
char buffer[];
buffer[i]=rec_data; |
In the code above, you have not declared any size for the buffer array.
Therefore, the compiler doesn't allocate any RAM to it. But then your
code writes to buffer[i]. What RAM location is it writing to ?
Fix this. Declare buffer with a suitable size so that it will hold all your
data. Be sure to allow an additional byte for the string terminator 0x00
at the end of every string.
| Quote: | | if(strcmp(buffer,"ok",2 )!=0) |
This line has a few bugs.
1. 'buffer' has no size.
2. You have "ok" in lower case. The response I have always seen from
any device that accept AT commands is the "OK" is in upper case.
3. Where did you see that strcmp() has 3 parameters ? What document
did you read that shows it has 3 parameters ?
4. Where did you see that strcmp() returns a non-zero value if the
strings match ? Again, what document did you read that says this ?
It's possible that you meant to use strncmp(). If so, you have to spell
the function name correctly. Details are very important in programming.
Everything will fail if you don't watch the details.
Your program might have other bugs. I didn't look any farther. |
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pathmasugu
Joined: 21 Feb 2014
Posts: 25
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| Posted: Tue Mar 18, 2014 1:28 am |
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dont compare direct string in strcmp function
dont use like this
if(strcmp(buffer,"ok")==0)
try use to following
char check[2]="ok";
.
.
.
if(strcmp(buffer,check)==0)
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ROCK RAJ |
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ILLIAS28
Joined: 11 Jan 2011
Posts: 42
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| Posted: Tue Mar 18, 2014 6:16 am |
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Thank you very much for your help "PCM programmer" and "pathmasugu".
You're right "PCMprogrammer" it must be strncmp and not strcmp and by adding "#device PASS_STRINGS=IN_RAM" my problem was resolved. I get no more error. I have added a size for my array buffer too.
many many thanks
_________________
i am newbe |
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ILLIAS28
Joined: 11 Jan 2011
Posts: 42
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| can't read gsm response |
| Posted: Mon Mar 24, 2014 10:38 am |
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could you please help me ,
what is wrong in the following code ,i can't read the answer of the gsm to "at" command.i always get error.
| Code: |
#include <16F876.h>
#device PASS_STRINGS=IN_RAM
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#fuses XT NOWDT NOPUT NOPROTECT BROWNOUT NOLVP NOCPD NOWRT NODEBUG
#use delay(clock=4000000) // you must use this line becuse the LCD.C use //the delay_us() functions
#use rs232(baud=9600,xmit=pin_c6,rcv=pin_c7)
#define use_portb_lcd TRUE
#include <lcd.c>
void main()
{
int i;
char *reponse , buffer[20];
unsigned char rec_data;
SET_TRIS_A( 0xFF );
lcd_init();
lcd_putc('\f');
printf(lcd_putc,"hallo");
DELAY_ms(3000);
lcd_putc('\f');
printf(lcd_putc,"pressez bouton");
for(;;)
{
if(!input(PIN_A0))
{
lcd_putc('\f');
printf(lcd_putc,"waiting...");
DELAY_ms(3000);
printf("at\r"); //send at command
i=0;
do
{
rec_data=getchar();
buffer[i]=rec_data; //save response in a string
i++;
}
while(rec_data!='\n');
//DELAY_ms(3000);
//if (memcmp("OK",&buffer,2) != 0)
reponse=strstr(buffer,"OK");
if (reponse == NULL)
//!if(strcmp(buffer,"OK")!=0) //see if response is "ok"
{
lcd_putc('\f');
printf(lcd_putc,"error");
DELAY_ms(3000);
}
else {
lcd_putc('\f');
printf(lcd_putc,"ready");
DELAY_ms(3000);
}
lcd_putc('\f');
printf(lcd_putc,"pressez bouton");
}
}
} |
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i am newbe |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Mon Mar 24, 2014 11:21 am |
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| Quote: | | i always get error. |
If you get an error, tell us what the error is, in detail. |
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ILLIAS28
Joined: 11 Jan 2011
Posts: 42
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| Posted: Mon Mar 24, 2014 11:41 am |
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THANKS PCM PROGRAMMER FOR YOUR INTEREST,
I mean that when i run the program, i get on my lcd display "error" but never "ready"".
As you can see in the code, i send at command and i read the answer from gsm through rs232((tx and rx on the pic16f876,connected to rx and tx of my gsm)), when the response is "OK" i display on the lcd "ready" otherwise i display "error".
_________________
i am newbe |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19510
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| Posted: Mon Mar 24, 2014 12:24 pm |
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A string needs to be null terminated.
When you receive the '\n', you need to write '\0' to the buffer so it has the termination. strstr, and other 'string' functions, _require_ the string to have the proper termination.
Add 'errors' to the RS232 declaration. Otherwise if data is received in the long delays, the RS232 receive will become hung.
The clock and fuse declarations should always be before all the includes except the processor definition. Sequence should be:
| Code: |
#include <16F876.h>
#device PASS_STRINGS=IN_RAM
#fuses XT NOWDT NOPUT NOPROTECT BROWNOUT NOLVP NOCPD NOWRT NODEBUG
#use delay(clock=4000000) // you must use this line becuse the LCD.C use //the delay_us() functions
#use rs232(baud=9600,UART1, ERRORS)
//end of processor setup - this should be completed _before_ loading
//anything else
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define use_portb_lcd TRUE
#include <lcd.c>
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ILLIAS28
Joined: 11 Jan 2011
Posts: 42
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| Posted: Mon Mar 24, 2014 5:09 pm |
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Thanks Ttelmah for your help,
What do you mean with "When you receive the '\n', you need to write '\0' to the buffer" which buffer are talking about and how can i do that?
_________________
i am newbe |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Mon Mar 24, 2014 10:36 pm |
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This is your routine which reads data and puts it in a buffer until you get \n.
| Quote: | do
{
rec_data=getchar();
buffer[i]=rec_data; //save response in a string
i++;
}
while(rec_data!='\n');
|
Look at your code while reading Ttelmah's comments. |
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ILLIAS28
Joined: 11 Jan 2011
Posts: 42
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| Posted: Tue Mar 25, 2014 9:39 am |
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thank's guys for your help it's very kind of you.
i did the corrections you told me ,and i have found a hardware problem too that i resolved.now it's working fine and i can send at commands from pic to gsm.the difficulty for me now is when receiving response or sms from gsm,how can i detect the end of it.'cause the "\n" isn't any more enough ,since some at commands response send many time "\n"
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