string into int

**doia** · 04-02-2010

I am trying to obtain data from a serial port. I managed to obtain the correct numbers to display on the screen with the following code:

Code:

char sbuf[256];
			for(unsigned int i=0; i<count; )
			{
				int len=0;
				int first_byte = i;
				for(int j=0;(j<24)&&(i<count);j++,i++)
				{
				len += sprintf(&sbuf[len], "%02X ", data[i]);
				if (i==1)
				{
					printf("\n%s", sbuf);
				}
				}

			}

So my output(sbuf) looks like this:
Hex value:
FF 00
01 24
44 FD
02 47........
Now I want to get this sbuf value and store into an unsigned int. Eg: FF 00 would become 65280.
But everytime I try to convert sbuf into a char or int I get the same number over and over again: FF 00 returns 100023 and 01 24 and all numbers return 100023.
I am really lost as to why this is happening can anyone enlighten me please?

**doia** · 04-02-2010

ok. so I changed my sprintf statement to :

Code:

len += sprintf(&sbuf[len], "%i ", data[i]);
				if (i==1)
				{
					printf("\n%s", sbuf);
					int isavar;
					isavar = atoi(sbuf);
					printf("\n dec %i",isavar);
				}

Only problem now is that atoi(sbuf) only gets the first part of my number. So:
if sbuf is: 136 34
isavar returns 136. And what I really want isavar to be is:8738
136 34 ->1000100 0100010 ->8738

**bernt** · 04-02-2010

It's because sbuf is "FF00", the characters 'F', 'F', '0', '0', and not the data 0xff00. You'll have to read it back in using scanf("%02X", &result) [ie, the same way you wrote the data].

EDIT: actually the spaces are gonna screw you up on this - you'll have to read in 2 values anyway. go with the second solution...

Or better yet, since you have the original data anyway, just put it together yourself:

Code:

/*bit-shift example*/
int low = 0x00;
int high = 0xFF;
int word = low + (high << 8); //or high*256 if you prefer

/*now word = 0xFF00*/

**doia** · 04-02-2010

I am still confused, how would I go about getting the "low" part. All I can seem to get is the high

**Subsonics** · 04-02-2010

If you can use shorts instead of ints, perhaps you could use this:

Code:

unsigned short num = (short)strtol(buf, NULL, 16);

**doia** · 04-02-2010

unsigned short still doesn't fix my problem:

Code:

if (i==1)
				{
					printf("\n%x",  data[i]);
					int isavar = (int)(data[i]);
					printf("\n dec %i",isavar);
				}

If I don't use my sbuf I don't know how to get the correct values out of data.
When I run the code above to just printf my original data (data[i]) I get the same value everytime ... and it's the wrong one. Meanwhile when I printf sbuf like I was doing before (see code in my last post) I get the correct ones.
So unless I can obtain the correct values from data[i] as a number I need to get the second part of what sbuf is holding (my 'low' part of the number)

**Subsonics** · 04-02-2010

I'm not sure I get you, but what datatype is data then?

**vart** · 04-02-2010

do you mean something like that:

Code:

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

int main()
{
    unsigned int x = 0xabcdFF23;
    unsigned char data[sizeof (unsigned)];
    int i;
    unsigned temp = x;
    char buf[256];
    int len = 0;
    char* pEnd = buf;
    printf ("%X\n", x);
    for(i = 0; i < sizeof (unsigned); i++)
    {
        data[i] = temp & 0xFF;
        temp >>= 8;
    }
    while(i> 0)
    {
        len += sprintf(buf+len,"%02X ", data[i-1]);
        i--;
    }
    printf("%s\n", buf);

    temp = 0;
    while(*pEnd)
    {
        unsigned char res = strtol(pEnd,&pEnd,16);
        temp <<= 8;
        temp |= res;
        pEnd++;
    }

     printf("%X\n",temp);
    return 0;
}

**quzah** · 04-02-2010

Code:

    unsigned int x = 0xabcdFF23;
    unsigned char data[sizeof (unsigned)];
    int i;
    unsigned temp = x;

Is there any particular reason that you specify 'unsigned' some times, and 'unsigned int' others?

Quzah.

**vart** · 04-02-2010

Originally Posted by quzah

Is there any particular reason that you specify 'unsigned' some times, and 'unsigned int' others?

laziness

**doia** · 04-05-2010

Originally Posted by vart

do you mean something like that:

yes that works great! thanks for all the help guys

Thread: string into int

Thread Tools

Search Thread

Display

string into int

Similar Threads

how to combine these working parts??

Code review

Something is wrong with this menu...

My graphics library

How do you search & sort an array?