Global variables.

[ebarnes]

I am using "Static" to define variable "RfidReq", but I still get this error message.

"Undefined identifier
The specified identifier is being used but has never been defined. Check the spelling."

I am declaring it in the Interupt, because when i declared it inthe main, i got the error in the interupt. *Sigh*

-----------------------------------------------------------
#int_RDA
void RDA_isr()
{
static char RfidReq[8];
static int CharCnt;
RfidReq[CharCnt]=getc();
putc(RfidReq[CharCnt]);
CharCnt++;
if(CharCnt>=8)
{
CharCnt=0;
}
}
---------------------------------------------------------
and using it here in Main.
---------------------------------------------------------
void main()
{
static int CharComp;
static char master[8];// this is the master key in decimal



setup_adc_ports(NO_ANALOGS|VSS_VDD);
setup_adc(ADC_OFF);
setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1);
setup_timer_1(T1_DISABLED);
setup_timer_2(T2_DISABLED,0,1);
setup_comparator(NC_NC_NC_NC);// This device COMP currently not supported by the PICWizard
enable_interrupts(INT_RDA);
enable_interrupts(INT_SSP);
enable_interrupts(INT_TIMER0);
enable_interrupts(GLOBAL);
setup_oscillator(OSC_4MHZ);


master[0]='0';///lsb
master[1]='6';
master[2]='9';
master[3]='1';
master[4]='2';
master[5]='7';
master[6]='1';
master[7]='5';///msb



while (CharComp >=-1)
{
if (RfidReq[CharComp] == master[CharComp])// this is the line the error occures on
CharComp++;
else
CharComp = -10;
}

}

----------------------------------------------------
when i compile, i get the error only on the specific variable.

[ckielstra]

Your poll is useless, by it's asynchronous nature an interrupt can never return a variable.
Explanation: As you can never know when the interrupt will occur, how and when were you going to test for the result?

[ebarnes]

Thank-you for your Critique, but You didn't address why I am getting the error.

[treitmey]

If the variable is updated in a isr it has to be declared in global scope.
so that it can be used outside your void RDA_isr(){} function.

Difference between static and global variables.
2nd paragraph of item 1.
http://c.ittoolbox.com/documents/popular-q-and-a/difference-between-static-global-variable-1596

[rnielsen]

Your static variable is defined inside of your ISR and can only be used inside the ISR. When you try to use a variable inside of main(), even though it has the same name, it is considered to be a completely different variable. You will need to declare a variable inside of main() to use it inside of main(). If you want to access the same variable inside of the ISR and inside of main() then you will need to declare it at the top of the code and make it a Global variable.

Also, It would not be a good idea to declare different variables with the same name inside of different functions. Even though the compiler will handle them properly, it may cause confusion for the programmer on which variable he is manipulating. Mistakes can creep into your code if you practice this type of programming.

Ronald

[ebarnes]

what is the syntax for defining a global variable? I cannot find it in the help sections.

[rberek]

Global variables have the same syntax as local variables, they are just declared outside of main or any other code block.

This is standard C syntax and is not specific to the CCS compiler, so it may not be discussed in the help files.

[iw2nzm]