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Dima49
Joined: 11 Apr 2005
Posts: 5
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| atoi question |
 Posted: Sun Apr 17, 2005 7:28 pm |
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hi,
I am a little stuck with the the code below; trying to code up a little controller board.
I am testing my rs232 comm code by writing to the pic and getting an input back via printf function. (I am using Hyperterminal on XP)
If I type in a number below 128 I get it back no prob. As soon as I move above this magic threshold the numbers become negative.
If PIC was a 32 bit processor and CCS had signed and unsigned ints I would understand what is going on, but currently I am a bit lost  <-- no pun intended...
As I see it, the problem is ether with the way Hyperterm views the data coming in or in my bonehead implementation of atoi function (I am voting for the later.)
if anyone has time to look and comment I would very much appreciate it.
d
| Code: |
char rxBuffer[4]; //the largest number recieved will be 255, that's 3 characters but termination (0x00) byte
#INT_RDA
void isr()
//generate an interrupt when serial-in buffer is filled
{
char rxValue;
int commandValue;
int rxBufferIndex=0;
output_high(PIN_B0);
rxValue=getc(); //read in the value
if(rxValue!='A') //see if NULL character (end of string)
{
rxBuffer[rxBufferIndex]=rxValue; //add a new value to the array
rxBufferIndex++;
}
else
{
rxBuffer[rxBufferIndex]=0x00; //cap off the buffer with a termination character (NULL)
rxBufferIndex=0; //reset RX buffer
commandValue=atoi(rxBuffer); //convert the characters which we recieved to intergers
printf("---------------->%d\n\r",commandValue);
}
}
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newguy
Joined: 24 Jun 2004
Posts: 1907
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| Posted: Sun Apr 17, 2005 7:34 pm |
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Just a quick comment....
The default integer size for CCS is 8 bits, so if the aoti function is doing a signed transfer, then that's the reason why anything over 127 would be negative, because the msb (bit 8) is a 1. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Sun Apr 17, 2005 8:08 pm |
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CCS provides the source code for atoi() in this folder:
c:\program files\picc\drivers\stdlib.h
The function declaration is:
signed int atoi(char *s) |
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Dima49
Joined: 11 Apr 2005
Posts: 5
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| thnx |
| Posted: Sun Apr 17, 2005 9:48 pm |
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thanx for pointing me in the right direction. I didn't realize that function definitions where available. <-- at least that part was quite bonehead-like
I think I might take the atol route and just give myself more bits to work with.
I also like the method used in:
http://ccsinfo.com/forum/viewtopic.php?t=20726&highlight=ascii2int8&sid=9523d7ad9a07bc8f0ee078dd9d605259
It's pretty elegant.
Pls tell if there are any other ways to tackle the problem, other wise thank you again. Help much appreciated.
d |
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Dima49
Joined: 11 Apr 2005
Posts: 5
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| ikk! beating my head against the wall AGAIN |
| Posted: Sat Apr 23, 2005 8:28 pm |
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OK sorry to resurrect this topic again but I am getting signed numbers AGAIN! one bit still manages to work against me 
Why am I getting negative numbers as soon as I reach 128? The function below is supposed to return unsigned int. I am not setting or clearing MSB anywhere.
Once again sorry to bring this question up again and would very much appreciate help in this matter.
dima
| Code: |
unsigned char rxBuffer[RX_BUFFER_SIZE];
unsigned int Ascii2Int()
//convert an ascii string to an interger
{
return((rxBuffer[0]&0x0f)*100+(rxBuffer[1]&0x0f)*10+(rxBuffer[2]&0x0f));
}
#INT_RDA
void isr()
//generate an interrupt when serial-in buffer is filled
{
char rxValue;
unsigned int commandValue;
static int rxBufferIndex=0;
output_high(PIN_B0);
rxValue=getc(); //read in the value
if(rxValue!='A') //see if NULL character (end of string) was passed
{
rxBuffer[rxBufferIndex]=rxValue; //add a new value to the array
rxBufferIndex++;
}
else
{
rxBuffer[rxBufferIndex]=0x00; //cap off the buffer with a termination character (NULL)
rxBufferIndex=0; //reset RX buffer
commandValue=Ascii2Int(); //convert the characters which we recieved to integer value
printf("---------------->%d\n\r",commandValue);
}
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Sat Apr 23, 2005 11:54 pm |
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Instead of getting sad, you should go into analysis mode.
You should question your code, and look up anything that
you don't completely understand in the manual or the Help file.
You should ask yourself what is the %d in the printf statement ?
Why is it there ?
Does it affect how the numbers are displayed ?
printf("---------------->%d\n\r",commandValue);
Then you can look it up in some document and notice
that there are many options for printf. Maybe one
of them is for signed numbers, and another is for
unsigned numbers, etc.
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vclib/html/_crt_printf_type_field_characters.asp
In other words, all of this stuff should be done before you get sad.  |
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