How to deal with float values..?

Hello all,

I am working on 16 bit adc ADS 7825, I've got output of it which is in form of 2's complement. I've also converted that hex value into decimal, now I want to display the voltage value like 2.45xx, 3.4267 etc., on six digit 7 segment.

So, I need to multiply the decimal value with 5V / 65536(16 bit). So I got float value to multiplied with the decimal. Now how to handle this float value calculation and how to display the resultant float value on 7 segment..?

I am using codevision avr and the controller is ATMEGA 128.

The code is given below::

#include <stdio.h>
#include <stdlib.h>

#define CLK PORTA.0
#define DATA PORTA.2
#define LATCH PORTA.1
#define A1 PORTA.3
#define A0 PORTA.4
#define byte PORTA.5
#define rc PORTA.6
#define busy PORTA.7

unsigned char digit[5];
void main(void)
{
unsigned char data,data2,data3,data4,i,j;
unsigned int final=0,fi2=0;

while(1)
{

rc = 1;
A1 = 0;
A0 = 0;
PORTG &= 0x00; // portg.2 (contc) = 0
byte = 0;
rc = 0;
delay_us(4);
rc = 1;
while(busy == 0);
data = PINC;
byte = 1;
for(i=0;i<1;i++) for(j=0;j<2;j++);
data2 = PINC;

data3 = ~ data;
data4 = ~ data2;

final = (data3<<8) + data4 + 1; // 2's complement

fi2=hex2dec(final); // getting decimal value



}
}

int hex2dec(unsigned int lnum)
{
unsigned char i=0;
unsigned int deci;
while(lnum > 10)
{
digit = lnum % 0x0a;
lnum = lnum / 0x0a;
i++;
}

deci = atoi (digit);
return deci;
}


NIKS

Hi

In order to display the A2D value on a 7 segment display you will need to convert the decimal number into plain char's separate them into segment and then add the decimal point

for example :you want to display : 6.55V

1) set it to mV reading :655
2)separate and convert to to ASCII( or to 7 seg data ) char : 0x36,0x35,0x35
3)send each char to seven Seg display
4)Set on the decimal point

All the best

Bobi

The microcontroller specialist

Instead of multiplying by 5/65536, multiply by 5000/65536. So u know that a result of 1000 means 1. Just put the point btw 1 and 0. Enjoy friend.

Hello all,

There is one more problem arises, The function hex2dec doesn't give output, when I run that code, it gives nothing... Can anyone tell me what's wrong with that funciton??

NIKS

There's a lot of confusion in your code. hex2dec doesn't work because you apply atoi() on numeric values, but it only works
for null terminated ASCII strings. Furthermore, I don't see the purpose of applying atoi(). The digit array contains already
the numeric values, that can be output to your display.

Hi,

I tried the code without atoi, you are right it works and gives the numeric value..
The new function for testing is like this..

void hex2dec(unsigned int lnum)
{
unsigned char i=0;
unsigned int deci;
while(lnum > 10)
{
digi = lnum % 0x0a;
lnum = lnum / 0x0a;
uart_digit(digi); // Display value for uart
i++;
}
delay_ms(500);
}

I am getting decimal value in uart..But i don't know exactly that how to go ahead and display the output on 7-segment..

I've to use this array and have to do some multiplications and then display it to 7 segment. But I am not able to get this value out of this function..

NIKS