As no one knows I will just post what I ended up doing which was to write my own function for convertion not ideal but it worked.
bool cdec2s32(char* text, s32 *destination)
{
s32 tempResult = 0;
char currentChar;
u8 numDigits = 0;
bool negative = FALSE;
bool warning = FALSE;
if(*text == '-')
{
negative = TRUE;
text++;
}
while(*text != 0x00 && *text != '\r') //while current character not null or carridge return
{
numDigits++;
if(*text >= '0' && *text <= '9')
{
currentChar = *text;
currentChar -= '0';
if((warning && ((currentChar > 7 && !negative) || currentChar > 8 && negative )) || numDigits > 10) // Check number not too large
{
tempResult = 2147483647;
if(negative)
tempResult *= -1;
*destination = tempResult;
return FALSE;
}
tempResult *= 10;
tempResult += currentChar;
text++;
if(numDigits >= 9)
{
if(tempResult >= 214748364)
{
warning = TRUE; //Need to check next digit as close to limit
}
}
}
else if(*text == '.' || *text == ',')
{
break;
}
else
return FALSE;
}
if(negative)
tempResult *= -1;
*destination = tempResult;
return TRUE;
}