need a sample of code to convert float to char array

userx51 · Sep 27, 2013

does any one has any code to convert float to char without using sprintf?.

jayanth.devarayanadurga · Sep 27, 2013

If you use mikroe compilers then it has FloatToStr() function.

Code C - [expand]
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//Global Variables
double FP_NUM;
char string[8];
 
//Function Prototypes
void floattostring(double FP_NUM);
 
//Sub Function
void floattostring(double FP_NUM) {
        double fpnumber;
        long int befdec, aftdec;
 
        fpnumber = FP_NUM;
 
        befdec = fpnumber;                      // Fractional part is truncated
                                                // 12.163456 becomes 12
        aftdec = fpnumber * 100;            // 12.163456 becomes 1216
        aftdec = aftdec - (befdec * 100);   // 1216 - 1200 = 16
 
 
        if (fpnumber < 1) {
                string[0] = '0';
                string[1] = '.';
                string[2] = (aftdec/10) + 48;
                string[3] = (aftdec/1)%10 + 48;
                string[4] = ' ';
                string[5] = ' ';
                string[6] = ' ';
                string[7] = '\0';
 
        }
 
        else if ((fpnumber >= 1) && (fpnumber < 10)) {
                string[0] = (befdec/1)%10 + 48;
                string[1] = '.';
                string[2] = (aftdec/10) + 48;
                string[3] = (aftdec/1)%10 + 48;
                string[4] = ' ';
                string[5] = ' ';
                string[6] = ' ';
                string[7] = '\0';
 
        }
 
        else if ((fpnumber >= 10) && (fpnumber < 100)) {
                string[0] = (befdec/10) + 48;
                string[1] = (befdec/1)%10 + 48;
                string[2] = '.';
                string[3] = (aftdec/10) + 48;
                string[4] = (aftdec/1)%10 + 48;
                string[5] = ' ';
                string[6] = ' ';
                string[7] = '\0';
 
        }
 
        else if ((fpnumber >= 100) && (fpnumber < 1000)) {
                string[0] = (befdec/100) + 48;
                string[1] = (befdec/10)%10 + 48;
                string[2] = (befdec/1)%10 + 48;
                string[3] = '.';
                string[4] = (aftdec/10) + 48;
                string[5] = ' ';
                string[6] = ' ';
                string[7] = '\0';
 
        }
        
        else if ((fpnumber >= 1000) && (fpnumber < 10000)) {
                string[0] = (befdec/1000) + 48;
                string[1] = (befdec/100)%10 + 48;
                string[2] = (befdec/10)%10 + 48;
                string[3] = (befdec/1)%10 + 48;
                string[4] = '.';
                string[5] = (aftdec/10) + 48;
                string[6] = ' ';
                string[7] = '\0';
 
        }
 
        else if ((fpnumber >= 10000) && (fpnumber < 100000)) {
                string[0] = (befdec/10000) + 48;
                string[1] = (befdec/1000)%10 + 48;
                string[2] = (befdec/100)%10 + 48;
                string[3] = (befdec/10)%10 + 48;
                string[4] = (befdec/1)%10 + 48;
                string[5] = '.';
                string[6] = (aftdec/10) + 48;
                string[7] = '\0';
 
        }
        
 
}
 
void main() {
      
      while(1) {
 
                      
           volt = 123.2364
                     
 
           floattostring(volt);
           Lcd_Out(1,1,string);
                     
 
      }
      
}

Venkadesh_M · Sep 27, 2013

Float to char or float to string??
why not using sprintf??
using Spirintf in a program could crash your program any time, better choice is using snprintf..
many compilers doesnt support float printing in printf so the easiest way is converting the float into a decimal number by multiplying it

Code C - [expand]
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float x = 34.567;
int a,b;
a = (int)x;
b = ((int)( x * 1000)) % 1000;
snprintf(str,8,"%d.%0.3d",a,b);

without using two this, your going to write lot of lines........

paulfjujo · Sep 27, 2013

Hello,

Venkadesh_M said:
many compilers doesnt support float printing in printf so the easiest way is converting the float
into a decimal number by multiplying it

Code C - [expand]

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float x = 34.567;
int a,b;
a = (int)x;
b = ((int)( x * 1000)) % 1000;
snprintf(str,8,"%d.%0.3d",a,b);

without using two this, your going to write lot of lines........

Yes, it's a very fast and simple solution,
but limited to 32767.0 and -32768.0 value
or use long int for a,b

userx51 · Sep 27, 2013

no mikroe compilers, no snprintf works. It takes a more low level c code.

FvM · Sep 27, 2013

no mikroe compilers, no snprintf works. It takes a more low level c code

Every C compiler has some kind of itoa() conversion or numeric print feature. And it's highly suggested to use thes built-in library functions, because a self-elaborated conversion as shown in post #2 maybe needs the tenfold code space.

paulfjujo · Sep 27, 2013

hello,

I checked it, you can not use code in post #3 for floating value over 32.767
maybe depend of what is an int ? for 8 bits µcontroller (as 16F or 18F) int is signed 16 bits , so -32768 to + 32767
if tested other soluce with MPLAB C18 , but near standard C.

Result get on watch register window is included inside this code , as comment.
You can see that that to handle floating and long int conversion is not so evident,
for big numbers.

Code:

// MPLAB C18 
// Test sur convertion Float to ASCII
// pieges sur arrondi
// Test_flot_2_string_130927.c_


#include "p18f26k22.h"
#define p18f26k22
#define Versus "Versus 130926 C18   "


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


//#define OSCILLATEUR_INTERNE

#ifdef OSCILLATEUR_INTERNE
#pragma config FOSC = INTIO67, FCMEN = OFF, PLLCFG=OFF            // CONFIG1H
#else
#pragma config FOSC = HSHP, PLLCFG=OFF, PRICLKEN=ON ,FCMEN=OFF      // quartz 10Mhz
#endif
#pragma config IESO=OFF,PWRTEN=OFF,BOREN=OFF,WDTEN=OFF,CCP2MX=PORTC1
#pragma config PBADEN=OFF,T3CMX=PORTC0,P2BMX=PORTC0,CCP3MX=PORTB5
#pragma config MCLRE=EXTMCLR,STVREN=OFF,LVP=ON,XINST=OFF,DEBUG=OFF
#pragma config CP0 = OFF, CP1 = OFF, CP2 = OFF, CP3 = OFF                    // CONFIG5L
#pragma config CPB = OFF, CPD = OFF                                          // CONFIG5H
#pragma config WRT0 = OFF, WRT1 = OFF, WRT2 = OFF, WRT3 = OFF                // CONFIG6L
#pragma config WRTB = OFF, WRTC = OFF, WRTD = OFF                            // CONFIG6H
#pragma config EBTR0 = OFF, EBTR1 = OFF, EBTR2 = OFF, EBTR3 = OFF            // CONFIG7L
#pragma config EBTRB = OFF                                                   // CONFIG7H


// Using Q=20Mhz  Clock 
#define CLOCK_FREQ 20000000L 
#define FOSC 10000000


#ifndef Byte
#define Byte unsigned char
#endif

char str[32];
float x,y ,z;
long int d,e; 
int  a,b;
int k;

void main()
{

//=========Zone for short tests===================
x= 34.567;
a = (int)x;
b = ((int) (x * 1000)) % 1000;
k=sprintf(str,"%8d%1c%3d",a,46,b);
/*  Problem if over 32.0
          6C8 str                          "      34.-969"
          6FC a                                         34
          6FE b                                       -969
 */         
x= 32.767;
a = (int)x;
b = ((int) (x * 1000)) % 1000;
k=sprintf(str,"%8d%1c%3d",a,46,b);
/*  here no problemo because  32*1000 < 32767
          6C8 str                          "      32.766"
          6FC a                                         32
          6FE b                                        766
 */ 
 
x= 34.567;
d = (long int)x;
e = ((long int) (x * 1000.0)) % 1000;
k=sprintf(str,"%8ld%1c%3ld",d,46,e);
/*  OK 
          6C8 str                          "        34.567"
          6F4 d                                        34
          6F8 e                                       567
 */  
 
 
 
x= 1234567.876;
d = (long int)x;
e = ((long int) (x * 1000.0)) % 1000;
k=sprintf(str,"%8ld%1c%3ld",d,46,e);
/*  Erreur in decimal part
          6C8 str                          "  1234567.936"
          6F4 d                                   1234567
          6F8 e                                       936
 */   

      
x= 1234567.876; 
y= modf(x,&z);    // <-  used to separate entire part and decimal part  see C18 Maths
d=(long int)z;
e=(long int)(y*1000.0);
k=sprintf(str,"%8ld%1c%3ld",d,46,e);
/*  OK, only rounded at 1/1000 decimale
          6C8 str                          "  1234567.875"
          6F4 d                                   1234567
          6F8 e                                       875
 */   


while(1);

Venkadesh_M · Sep 28, 2013

paulfjujo said:
hello,
I checked it, you can not use code in post #3 for floating value over 32.767
maybe depend of what is an int ? for 8 bits µcontroller (as 16F or 18F) int is signed 16 bits , so -32768 to + 32767
if tested other soluce with MPLAB C18 , but near standard C.

I have just shown an Idea and I believe you can use that method for any float value with any compiler... Nothing is impossible with C...
and also thanks for constructing such a test case.....

and here is some more better idea..

Code C - [expand]
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#include <stdio.h>
main()
{
float x = 34.567;
 
int a,b;
float c;
 
a = (int)x;                     // taking integral part
c = x - (int) x;                // taking fractional part
b = ((int)( c * 1000)) % 1000;    // fractional part to intger
 
printf("%d.%0.3d",a,b);
}

- - - Updated - - -

For OP's problem

Code C - [expand]
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void float_to_string(float x, char* string)
{
                string[0] = (int) ( x / 1000 ) % 10 + '0';
                string[1] = (int) ( x / 100  ) % 10 + '0';
                string[2] = (int) ( x / 10   ) % 10 + '0';
                string[3] = (int) ( x / 1    ) % 10 + '0';
                string[4] = '.';
                string[5] = (int) ( x * 10   ) % 10 + '0';
                string[6] = (int) ( x * 100  ) % 10 + '0';
                string[7] = (int) ( x * 1000 ) % 10 + '0';
                string[8] = '0';
                string[9] =  0 ;
}

you can use this function but the decimal places will be fixed....

need a sample of code to convert float to char array

userx51

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jayanth.devarayanadurga

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Venkadesh_M

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paulfjujo

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userx51

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FvM

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Venkadesh_M

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Code C - [expand]
1 2 3 4 5	float x = 34.567; int a,b; a = (int)x; b = ((int)( x * 1000)) % 1000; snprintf(str,8,"%d.%0.3d",a,b);

Code C - [expand]
1 2 3 4 5	float x = 34.567; int a,b; a = (int)x; b = ((int)( x * 1000)) % 1000; snprintf(str,8,"%d.%0.3d",a,b);

need a sample of code to convert float to char array

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