error message: " **** was not declared in this scope "

Projects Programming
1

Hey guys, I'm working on a fairly simple sketch that reads some data addresses (#3-33) on an RFID card, printing the results to the monitor. I had another variant of this sketch working before, but I am trying to make it a little more elegant and have run into a problem. Whenever i try to compile the sketch, I receive the error message:

FINAL_read_whole_card_with_checking:3: error: 'whichSpace' was not declared in this scope
FINAL_read_whole_card_with_checking:31: error: redefinition of 'int readCard'
FINAL_read_whole_card_with_checking:3: error: 'int readCard' previously defined here

I have read and re-read my code, but I can't figure out what the IDE isn't liking. My code is below (sorry that it isn't formatted nicely, but that's another problem I'm having: clicking "copy for forum" returns "Exception in thread "AWT-EventQueue-0" java.lang.ArrayIndexOutOfBoundsException: 40")

Here's my code:

#include <NewSoftSerial.h>
#define RFID_READ 0x01
#define txPin 6
#define rxPin 8

int firstByte;
int secondByte;
int thirdByte;
int fourthByte;
int whichSpace;

NewSoftSerial mySerial(rxPin, txPin);

void setup()
{
  Serial.begin(9600);
  Serial.println("Read RFID addresses #3-33:");
  mySerial.begin(9600);
  pinMode(txPin, OUTPUT);     
  pinMode(rxPin, INPUT);      
}

void suppressAll()                            
{
  if(mySerial.available() > 0)
  { 
    mySerial.read();
    suppressAll();
  }
}

int readCard(whichSpace)
{
   mySerial.print("!RW");
   mySerial.print(RFID_READ, BYTE);
   mySerial.print(whichSpace, BYTE);

   if(mySerial.available() > 0) 
   {   
     val = mySerial.read();                        
     if (val != 1)                            
     {
       suppressAll();
       read(whichSpace);
     }   
  first = mySerial.read();
  second = mySerial.read();   
  third = mySerial.read();
  fourth = mySerial.read();
}
}

void loop()
{
  for (whichSpace = 3; whichSpace <= 33; whichSpace++)
  { 
    readCard(whichSpace)
    
    if(mySerial.available() > 0) {       
        val = mySerial.read();
        Serial.print(whichSpace);
        Serial.print(":"); 
        Serial.print(firstByte, DEC);
        Serial.print(" , ");
      }

      if(mySerial.available() > 0) {        
        val = mySerial.read();
        Serial.print(secondByte, DEC);
        Serial.print(" , ");
      }

      if(mySerial.available() > 0) {       
        val = mySerial.read();
        Serial.print(thirdByte, DEC);
        Serial.print(" , ");
      }

      if(mySerial.available() > 0) {          
        val = mySerial.read();
        Serial.println(fourthByte, DEC);
      }   

      delay(100);
    }
  }
}

Thanks for any/all help you can give!

2

You are defining a function with a parameter supposedly passed to it that exists already. Any parameter you pass must be unique in the function therefore you need to do at least:-
int readCard(int whichSpace) {
Note that the variable whichSpace used inside the function will not be the same as that defined outside to function. Is that what you want?

3

Change

int readCard(whichSpace)

to

int readCard(int whichSpace)

To get rid of the whichSpace error.

As Grumpy_Mike already pointed out, you're using two sets of whichSpace - because this one was 'hiding' the global one you defined at the top, the function saw it as a new variable, and since you didn't say specifically that it was an int, it complained.

However, you have another issue: doing duplicate variables like this makes for confusing code. You should rename one, or better yet get rid of one:

  • get rid of the global entry at the top, in which case means adding this to the start of loop():
int whichSpace=0;

or if the global value is needed, get rid of the parameter to int readCard(int whichSpace):

int readCard(void)

Also, the loop() has too many '}' braces in it.

4

thanks for the responses guys. I've got it working now...adding the int in front of whichspace did the trick.

int readCard(int whichSpace)
5 
[code]Warning:  This code will PROBABLY work but since it calls itself recursively it might crash the stack:

{code]
void suppressAll()                            
{
  if(mySerial.available() > 0)
  { 
    mySerial.read();
    suppressAll();
  }
}

This version has the same effect without the same risk:

void suppressAll()                            
{
  while (mySerial.available() > 0)
  { 
    mySerial.read();
  }
}

[/code]

6

thanks for the tip john, but that is not an issue. The recursion is limited by the

 if(mySerial.available() > 0)

The way the RFID reader works, there are 5 bytes reported when an address on the card is read: the first is a status byte (OK or error) and then 4 data bytes. So the recursion will only run 5 times, and then mySerial.available (which does just what you would think, reports the number of unread bytes) will be equal to zero, breaking the loop.

7

thanks for the tip john, but that is not an issue

There is an issue: the recursive version uses more stackspace, which could result in out of RAM (very small chance OK). Therefor Johns iterative version is to be prefered.