Type conversion - string of characters to integer

Question

Hello I am writing my program in C, using PSoC tools to program my Cypress development kit. I am facing an issue regarding type conversion of a string of characters collected in my circular buffer (buffer) to a local variable "input_R", ultimately to a global variable st_input_R. The event in my FSM calling this action function is given below:

---

void st_state_5_event_0(void)   //S6 OR S4
{   
    char buffer[ST_NODE_LIMIT] = {0};
    st_copy_buffer(buffer);
    uint32 input_R = {0};
    mi_utoa(input_R, buffer);

    if ((input_R >= 19000) && (input_R <= 26000))
    {   
        st_input_R = input_R;
        _st_data.state = ST_STATE_6; 
    }
    else
    {
        _st_data.status = ST_STATE_4;
    }
    UART_1_Stop();

    st_stop();

    st_empty_buffer();
}  

---

ST_NODE_LIMIT = 64 st_copy_buffer copies the the numbers I type in using hyper terminal to the circular buffer named "buffer". input_R is the 32 bit integer I want the buffer content to be converted to. mi_utoa is the function I am using for converting the contents in the buffer to input_R and is detailed below:

---

uint8 mi_utoa(uint32 number, char *string)
{
    uint8 result = MI_BAD_ARGUMENT;

    if (string != NULL)
    {
        uint8 c = 0;
        uint8 i = 0;
        uint8 j = 0;

        do
        {
            string[i++] = number % 10 + '0';
        } while ((number /=10) > 0);

        string[i] = '\0';

        for (i = 0, j = strlen(string) - 1 ; i < j ; i++, j--)
        {
            c = string[i];
            string[i] = string[j];
            string[j] = c;
        }

        result = MI_SUCCESS;
    }

    return result;
}

---

The problem is, suppose if I enter 21500(+\r), the mi_utoa function converts the first digit to 0 the second digit to \000 while the other digits including the carriage return "\r" remains unaltered. As a result the input_R is NOT = 21500. Its happening for any string of digits I input. So the condition "if ((input_R >= 19000) && (input_R <= 26000))" is never satisfied. Hence the FSM returns to state 4 all the time and I am going in circles.

Can you please advice where the bug is in the mi_utoa function? Let me know if you want to know any other details.

Answer 1

Your function st_state_5_event_0() sets the value input_R to zero. Then you call mi_utoa(), which converts the value input_R to an ascii string, "0".

void st_state_5_event_0(void)   //S6 OR S4
{   
    char buffer[ST_NODE_LIMIT] = {0};
    //what is the value of buffer after this statement?
    st_copy_buffer(buffer);
    //the value of input_R after the next statement is =0
    uint32 input_R = {0};
    //conversion of input_R to string will give ="0"
    mi_utoa(input_R, buffer);

    if ((input_R >= 19000) && (input_R <= 26000))
    {   
        st_input_R = input_R;
        _st_data.state = ST_STATE_6; 
    }
    //...
}

You probably want a function which converts your ascii buffer to a number.

uint8
mi_atou(uint32* number, char *string)
{
    uint8 result = MI_BAD_ARGUMENT;

    if (!string) return result;
    if (!number) return result;
    uint8 ndx = 0;
    uint32 accum=0;
    for( ndx=0; string[ndx]; ++ndx )
    {
        if( (string[ndx] >= '0') && (string[ndx] <= '9') )
        {
            accum = accum*10 + (string[ndx]-'0');
            //printf("[%d] %s -> %d\n",ndx,string,accum);
        }
        else break;
    }
    //printf("[%d] %s -> %d\n",ndx,string,accum);
    *number = accum;
    result = MI_SUCCESS;
    return result;
}

Which you would call by providing the address of the number to store the result,

    mi_atou(&input_R, buffer);