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nicotec
Joined: 07 Nov 2008
Posts: 60
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| IF statement not works |
 Posted: Fri Feb 13, 2009 9:16 am |
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Dear user, I need of your help since IF statement in my code doesn't work; could someone help me how to write in correct form the IF statement?
Thanks in advance and regards
| Code: | #include <input.c>
char temp[6];
#int_rda
void Serial_isr()
{
char string[6], term[3], *ptr;
char *valore;
char *comando;
printf("Enter string: ");
get_string(temp, sizeof(temp));
printf("\n\rReceived: %s \n\r", temp);
strcpy(string,temp);
strcpy(term,",");
ptr = strtok(string, term);
comando=ptr;
while(ptr!=0) {
//puts(ptr);
valore=ptr;
ptr = strtok(0, term);
}
if(comando!="55")
{
printf("\n\rComando= %s \n\r", comando);
printf("\n\rValore= %s \n\r", valore);
}
} |
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Ttelmah
Guest
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| Posted: Fri Feb 13, 2009 10:53 am |
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The reason the 'if' doesn't work, is that you cannot compare strings with the '!=' test. This _only_ applies for numeric values.
However, consider doing this all a completely different way. You are really 'abusing' the point of the interrupt. The idea of a serial ISR, should be to get just the _one_ character that is waiting in the hardware buffer. In your ISR, you are getting multiple characters, and outputting even more. Since potentially you are in the ISR, for 12 character times, before you even read a character, the hardware buffer (just two characters), can easily be overloaded, resulting in loss of characters (at the least), and hanging the UART (at the worst).
Do a search here about this. Unless you really know what you are doing, you should keep interrupt handlers short. If you want a 'input routine' triggered by the arrival of the first character, use something like the ex_sisr code, but add a flag, so that as soon as the interrupt is triggered, your main code calls the actual input routine. Avoid doing complex tasks like this in the ISR.
Best Wishes |
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nicotec
Joined: 07 Nov 2008
Posts: 60
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| Posted: Fri Feb 13, 2009 12:42 pm |
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above pic24 has 4 character buffer, so there are no risk to lost since I send only 5 char not so quickly; could you hel me to solve IF statement problem?
thanks |
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nicotec
Joined: 07 Nov 2008
Posts: 60
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| Posted: Fri Feb 13, 2009 1:17 pm |
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Please provide me a solution on if statement; i tried a lot of combination like =='55' ="55" but since i'm new user i need of your help.
thanks |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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nicotec
Joined: 07 Nov 2008
Posts: 60
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| Posted: Fri Feb 13, 2009 2:11 pm |
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Thanks, so I can change my code as follows?
| Code: | #include <input.c>
char temp[6];
#int_rda
void Serial_isr()
{
char string[6], term[3], *ptr;
char *valore;
char *comando;
char *pan_chk;
strcpy(pan_chk,"55");
printf("Enter string: ");
get_string(temp, sizeof(temp));
printf("\n\rReceived: %s \n\r", temp);
strcpy(string,temp);
strcpy(term,",");
ptr = strtok(string, term);
comando=ptr;
while(ptr!=0) {
//puts(ptr);
valore=ptr;
ptr = strtok(0, term);
}
if (strcmp(comando,pan_chk)!=1)
{
printf("\n\rComando= %s \n\r", comando);
printf("\n\rValore= %s \n\r", valore);
}
} |
What do You think?
Regards |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Fri Feb 13, 2009 2:30 pm |
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| Quote: | | if (strcmp(comando,pan_chk)!=1) |
There is no guarantee that strcmp() will return a value of 1.
If the strings are equal, it returns a value of 0.
If they are not equal, it returns a positive or negative number.
You need to get a book on C, or read an online tutorial on C.
In other words, we don't want to teach how to use every ordinary
C function such as strcmp(). You need to get a book about it. |
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nicotec
Joined: 07 Nov 2008
Posts: 60
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| Posted: Fri Feb 13, 2009 2:33 pm |
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Sorry to disturb, I have already ordered a book and waiting it to receive.
Regards |
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