LCD and float question

pxds · Apr 27, 2010

I'm on dire need of displaying a float value on the LCD. The problem is, i can't do it

So far i've tried:

void func(void){
float x=3.14;
char buf[16];
sprintf(buf,"%f",x);
*send buf to the LCD*
}

Also tried the code on **broken link removed** wich converts float to string.

Both have failed and now i need your help.

Pommie · Apr 28, 2010

You could print the integer part and then do a fixed number of decimal places.

Something like,

Code:

    float x=3.1416;
    myint=(int)x;
    //send myint to LCD
    //send decimal point to LCD
    x-=myint;	//keep only decimal part
    for(i=0;i<4;i++){
        x*=10;
        myint=(int)x;
        x-=myint;
        //send myint to LCD
    }

Mike.

pxds · Apr 28, 2010

didn't work :/ i even tried something similar, where i divide the float into high and low int parts. something like:

Code:

        float f;
	int hi, lo;
	char buf[16];
        f = 25.64;
	hi = (int)f;
	lo = (int)(f - hi)*100;
        sprintf(buf,"%d.%d", hi, lo);
        // send buf to LCD

but all i get on the LCD is 25.0, any help?

pxds · Apr 28, 2010

char buf[8];
sprintf(buf,"%d.%02u", (int)f , ((int) ((f)-(int)f) * 100) );

this code was taken from Microchip oficial forum, but it gives the same 25.00 on the LCD. damn this is starting to bug me...

nsaspook · Apr 28, 2010

pxds said:
didn't work :/ i even tried something similar, where i divide the float into high and low int parts. something like:

Code:

float f; int hi, lo; char buf[16]; f = 25.64; hi = (int)f; lo = (int)(f - hi)*100; sprintf(buf,"%d.%d", hi, lo); // send buf to LCD

but all i get on the LCD is 25.0, any help?

Try this.
Multiply your floatx1000 into a long:

buf=voltfp((unsigned long) f*1000.0), buf);

Code:

char* voltfp(unsigned long millvolts, char *strprt)             // convert unsigned long (millvolts) to voltage string
{
    long                        iw = 0, ip = 0;
    float                       voltfrak;
    voltfrak = (float)millvolts / 1000;
    iw = (long)((float)voltfrak);
    ip = (long)((float)voltfrak * 100) - iw * 100;
    sprintf(strprt, "%d.%02d", (int)iw, (int)ip);
    return strprt;
}

Code:

int     ABS(int i)
{
    if (i < 0)
        return -i;
    else
        return i;
}

char* ahfp(long millah, char *strprt)           // convert long (.1 of Ah) to Ah string
{
    int                         iw = 0, ip = 0;
    float                       ahfrak;
    char                        sign = '+';

    if (millah < 0) sign = '-';

    ahfrak = (float)millah / 10;
    iw = (long)((float)ahfrak);
    ip = (long)((float)ahfrak * 10) - iw * 10;
    sprintf(strprt, "%c%d.%01d", sign, ABS(iw), ABS(ip));
    return strprt;
}

LCD and float question

pxds

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Pommie

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pxds

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pxds

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nsaspook

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