Thread: Converting an int to an address in an array

Hello. This is my first post and I welcome any and all advice on this particular program I am writing. I am trying to take any int value and convert it to a constant address off an array. For instance, if I enter the value 8, the output should be 0x08 as a string. I suspect there maybe a simpler way of doing this, but I am at a loss. I get the following errors when I compile:

main.c:54: warning: passing arg 1 of `ConvertStringToTable' makes integer from pointer without a cast
main.c:57: error: syntax error before '(' token
main.c:57:17: warning: multi-character character constant
main.c: In function `ConvertStringToTable':
main.c:61: error: syntax error at end of input

Eventually I want to take micro controller output as an int value and produce a matching address which I will use for an on screen display, but I'd like to get this simpler version working first.

Code:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

// 
// defining constants
const unsigned char charcodetable[] =
{
    0x01,0x02,0x03,0x04,0x05,0x06,0x07,0x08,0x09,0x0A,
};


const unsigned char ascii_table[] =
{
    '1','2','3','4','5','6','7','8','9','0',
};

unsigned char ConvertStringToTable (unsigned char data)
{
	unsigned char outchar=0x99;
	unsigned int i;

    for (i=0; i< sizeof(ascii_table); i++)
    {
        if (data == ascii_table[i])
        {
            outchar = charcodetable[i];
           break; 
        }
    }
	
    if (outchar!=0x99)
	{
		return outchar;	
	}
	else
	{
		return data;
	}

int main() 
{
    int num = 1;
    unsigned char buf[15];
    unsigned char dummy;
    
     itoa (num, buf, 10);

	printf("%s\n", buf);
	
    do 
	{
	dummy = ConvertStringToTable (buf);
	printf ("%s\n",dummy);
	
    } (dummy != '0x99');
    
    System ("Pause");
	return 0;
}

If you want to convert the integer to a hexadecimal value you can use sprintf or snprintf.

The compiler errors tell you where to look.

Line 57, it's a do while loop.

Code:

do 
	{
	dummy = ConvertStringToTable (buf);
	printf ("%s\n",dummy);
	
    } (dummy != '0x99');

Should be:

Code:

do 
	{
	dummy = ConvertStringToTable (buf);
	printf ("%s\n",dummy);
	
    } while (dummy != '0x99');

Line 54 should tell you to look at the data type you're passing the the function ConvertStringToTable. When you look at the function there's quite a few issues.. If you don't want to use sprintf etc then you need to take a look at the function.

Some questions you might want to try answering:
1. Why are you using the size of the ascii_table to parse the string data.
2. Is the function parameter correct - expecting a single character?
3. Is the function return value really meant to be a character - if so why are you printing a string in main.
4. '0x99' refers to a character (http://www.ieee.li/computer/ascii.htm

Apologies if this isn't very helpful.

I'm not clear why you don't simply use an array of pointers. Aren't regular ptr addresses what you want?

Originally Posted by saeculum

Some questions you might want to try answering:
1. Why are you using the size of the ascii_table to parse the string data.
2. Is the function parameter correct - expecting a single character?
3. Is the function return value really meant to be a character - if so why are you printing a string in main.
4. '0x99' refers to a character (http://www.ieee.li/computer/ascii.htm

Apologies if this isn't very helpful.

1. I just want it cycle through numbers 0-9 for each decimal place. I don't want it to loop more than the number of digits in the original int value.

2. I want it to convert one character at a time within the function. This is so I can just do a SPI_WRITE for each address within the function itself. This will be implemented later.

3. This is just an arbitrary statement. I wanted to see what the output of the string is.

4. These aren't the real ASCII characters, this chip I am using has a different address associated with each number. For instance 7, is actually 0x07.

Originally Posted by Adak

I'm not clear why you don't simply use an array of pointers. Aren't regular ptr addresses what you want?

I have very limited experience working with pointers. Is the address associated with an integer match to that of the table of ascii_table[] and charcodetable[]? If so, it would be much simpler to just output the pointer address.

So instead of making tables I could just send values 0-9 to the display registers directly? Say my integer is num = 1234, could I send num[3] to the display register? would num [3] be equal to 1 or 1000 in this case? I thought I would have to convert everything to a string first because I want to interpret the number 1 in the number 1234 as 0x01 and not 3E8 (which is 1000).